Download natural heritage zones: earth sciences

NATURAL HERITAGE ZONES:
EARTH SCIENCES
John E. Gordon, R. George Lees,
Katherine F. Leys, Colin C. J. MacFadyen, Geeta Puri,
Robert Threadgould and Vanessa Kirkbride
CONTENTS
PART 1 SCOTLAND’S EARTH HERITAGE
10
Summary
11
1
Introduction
12
2
Geology
14
2.1
The geological framework
14
2.2
Understanding the Earth: Scotland’s geology in a worldwide context
25
3
4
5
Palaeontology
27
3.1
27
Key elements of Scottish palaeontology
Geomorphology
30
4.1
Pre-glacial landforms
30
4.2
Quaternary landforms and deposits
35
4.3
Coastal geomorphology
50
4.4
Fluvial geomorphology
55
4.5
Mass movement
59
4.6
Caves and karst
64
Soils
5.1
66
Scottish soil types
66
6
Scotland’s role in the history of geology and geomorphology
69
7
Knowledge and state of the resource
70
7.1
National datasets
70
7.2
Geology and palaeontology
71
7.3
Geomorphology
71
7.4
Soils
72
8
Trends
73
8.1
Trends in coastal evolution
73
8.2
Trends in river channel change
73
8.3
Mass movements as environmental indicators
74
Page 2
10 January, 2002
9
10
Pressures and threats
76
9.1
76
Pressures and impacts
References
81
Annex 1: The beaches of Scotland series
84
Annex 2: The coastal cells of Scotland series
85
Annex 3: Shoreline management plans and shoreline assessments
86
PART 2 ZONAL DESCRIPTIONS
87
ZONE 1 SHETLAND
89
1
Highlights
89
2
Geology
89
3
Palaeontology
91
4
Geomorphology
91
5
Soils
93
6
Summary of key Earth science features in Shetland
94
7
Pressures and trends
94
8
State of the resource
95
9
Bibliography
95
10
Maps
96
ZONE 2 NORTH CAITHNESS AND ORKNEY
97
1
Highlights
97
2
Geology
97
3
Palaeontology
98
4
Geomorphology
98
5
Soils
101
6
Summary of key Earth science features in North Caithness and Orkney
101
7
Pressures and trends
102
8
State of the resource
103
9
Bibliography
103
10
Maps
104
ZONE 3 WESTERN ISLES
105
1
Highlights
105
2
Geology
105
Page 3
10 January, 2002
3
Geomorphology
107
4
Soils
111
5
Summary of key Earth science features in the Western Isles
111
6
Pressures and trends
111
7
State of the resource
112
8
Bibliography
112
9
Maps
113
ZONE 4 NORTH-WEST SEABOARD
115
1
Highlights
115
2
Geology
115
3
Palaeontology
118
4
Geomorphology
119
5
Soils
121
6
Summary of key Earth science features in the North-West Seaboard
122
7
Pressures and trends
123
8
State of the resource
123
9
Bibliography
123
10
Maps
124
ZONE 5 THE PEATLANDS OF CAITHNESS AND SUTHERLAND
125
1
Highlights
125
2
Geology
125
3
Palaeontology
127
4
Geomorphology
128
5
Soils
130
6
Summary of key Earth science features in the Peatlands of Caithness and Sutherland
130
7
Pressures and trends
131
8
State of the resource
132
9
Bibliography
132
10
Maps
133
ZONE 6 WESTERN SEABOARD
134
1
Highlights
134
2
Geology
134
3
Palaeontology
139
4
Geomorphology
140
5
Soils
142
6
Summary of key Earth science features in the Western Seaboard
143
Page 4
10 January, 2002
7
Pressures and trends
144
8
State of the resource
144
9
Bibliography
144
10
Maps
145
ZONE 7 NORTHERN HIGHLANDS
146
1
Highlights
146
2
Geology
146
3
Palaeontology
148
4
Geomorphology
149
5
Soils
150
6
Summary of key Earth science features in the Northern Highlands
151
7
Pressures and trends
151
8
State of the resource
152
9
Bibliography
152
10
Maps
152
ZONE 8 WESTERN HIGHLANDS
154
1
Highlights
154
2
Geology
154
3
Palaeontology
156
4
Geomorphology
156
5
Soils
158
6
Summary of key Earth science features in the Western Highlands
158
7
Pressures and trends
158
8
State of the resource
159
9
Bibliography
159
10
Maps
160
ZONE 9 NORTH-EAST COASTAL PLAIN
161
1
Highlights
161
2
Geology
161
3
Palaeontology
162
4
Geomorphology
163
5
Soils
164
6
Summary of key Earth science features in the North East Coastal Plain
165
7
Pressures and trends
165
8
State of the resource
166
9
Bibliography
166
Page 5
10 January, 2002
10
Maps
ZONE 10 CENTRAL HIGHLANDS
167
168
1
Highlights
168
2
Geology
168
3
Geomorphology
169
4
Soils
170
5
Summary of key Earth science features in the Central Highlands
170
6
Pressures and trends
171
7
State of the resource
171
8
Bibliography
171
9
Maps
171
ZONE 11 CAIRNGORM MASSIF
172
1
Highlights
172
2
Geology
172
3
Geomorphology
173
4
Soils
176
5
Summary of key Earth science features in the Cairngorm Massif
176
6
Pressures and trends
177
7
State of the resource
177
8
Bibliography
178
9
Maps
179
ZONE 12 NORTH-EAST GLENS
180
1
Highlights
180
2
Geology
180
3
Palaeontology
181
4
Geomorphology
182
5
Soils
182
6
Summary of key Earth science features in the North East Glens
183
7
Pressures and trends
183
8
State of the resource
184
9
Bibliography
184
10
Maps
184
ZONE 13 LOCHABER
185
1
Highlights
185
2
Geology
185
3
Geomorphology
187
Page 6
10 January, 2002
4
Soils
189
5
Summary of key Earth science features in Lochaber
189
6
Pressures and trends
189
7
State of the resource
190
8
Bibliography
190
9
Maps
191
ZONE 14 ARGYLL WEST AND ISLANDS
192
1
Highlights
192
2
Geology
192
3
Palaeontology
196
4
Geomorphology
197
5
Soils
200
6
Summary of key Earth science features in Argyll West and Islands
200
7
Pressures and trends
201
8
State of the resource
202
9
Bibliography
202
10
Maps
203
ZONE 15 BREADALBANE AND EAST ARGYLL
204
1
Highlights
204
2
Geology
204
3
Palaeontology
205
4
Geomorphology
206
5
Soils
206
6
Summary of key Earth science features in Breadalbane and East Argyll
207
7
Pressures and trends
207
8
State of the resource
208
9
Bibliography
208
10
Maps
208
ZONE 16 EASTERN LOWLANDS
209
1
Highlights
209
2
Geology
209
3
Palaeontology
212
4
Geomorphology
212
5
Soils
216
6
Summary of key Earth science features in Eastern Lowlands
216
7
Pressures and trends
217
Page 7
10 January, 2002
8
State of the resource
218
9
Bibliography
219
10
Maps
219
ZONE 17 WEST CENTRAL BELT
221
1
Highlights
221
2
Geology
221
3
Palaeontology
223
4
Geomorphology
224
5
Soils
226
6
Summary of key Earth science features in the West Central Belt
226
7
Pressures and trends
227
8
State of the resource
228
9
Bibliography
228
10
Maps
229
ZONE 18 WIGTOWN MACHAIRS AND OUTER SOLWAY
230
1
Highlights
230
2
Geology
230
3
Palaeontology
232
4
Geomorphology
232
5
Soils
233
6
Summary of key Earth science features in Wigtown Machairs and Outer Solway
233
7
Pressures and trends
234
8
State of the resource
234
9
Bibliography
235
10
Maps
235
ZONE 19 WESTERN SOUTHERN UPLANDS AND INNER SOLWAY
236
1
Highlights
236
2
Geology
236
3
Palaeontology
238
4
Geomorphology
238
5
Soils
240
6
Summary of key Earth science features in the Western Southern Uplands and Inner Solway
240
7
Pressures and trends
241
8
State of the resource
242
9
Bibliography
243
10
Maps
244
Page 8
10 January, 2002
ZONE 20 BORDER HILLS
245
1
Highlights
245
2
Geology
245
3
Palaeontology
247
4
Geomorphology
247
5
Soils
248
6
Summary of key Earth science features in the Border Hills
248
7
Pressures and trends
249
8
State of the resource
250
9
Bibliography
250
10
Maps
250
ZONE 21 MORAY FIRTH
251
1
Highlights
251
2
Geology
251
3
Palaeontology
254
4
Geomorphology
254
5
Soils
257
6
Summary of key Earth science features in the Moray Firth
257
7
Pressures and trends
257
8
State of the resource
258
9
Bibliography
258
10
Maps
259
Page 9
10 January, 2002
PART 1
SCOTLAND’S EARTH
HERITAGE
Page 10
10 January, 2002
Summary
1
For a relatively small area, Scotland demonstrates an exceptional geological and
geomorphological diversity, a legacy of its prolonged history of some three billion years and
its position at the crossroads of colliding and rifting continents. Of particular note are:
•
•
•
•
•
the length of the geological record and the range of rock types and geological processes
and environments represented;
the rich and diverse fossil record;
the geomorphological diversity, reflecting the variations in underlying geology, ice-age
processes and environmental change, and postglacial and contemporary processes;
the range of soils, reflecting the variations in parent materials, topography and
hydrology;
Scotland’s role in the history of geology and geomorphology.
2
Scotland’s geology, geomorphology and soils underpin many other aspects of the
natural heritage. They are a strong influence on the character and key features of many of
the Natural Heritage Zones through links with landscape, habitats and ecosystems.
3
Part 1 of this report systematically reviews the main features of interest of the Earth
heritage of Scotland and their importance. It summarises the current state of knowledge and
the principal pressures on the resource. Where they are known, trends in the resource are
also reviewed.
4
Part 2 reviews the Earth science interests of each of the 21 Natural Heritage Zones
and highlights the key features that make each zone special.
Page 11
10 January, 2002
1
Introduction
The geological and geomorphological inheritance of Scotland – our Earth heritage – is a
source of considerable diversity in many of the physical factors that influence the character
and key features of Natural Heritage Zones. This diversity exerts a profound influence upon
the natural heritage, and is the foundation for landscapes, soils, habitats, species, land use
and recreation. There is both a relict aspect to this, in the form of the shaping of the
landscape and the provision of the basic materials and support systems for soil, habitat and
ecosystem development, and an active element, in the form the geomorphological and soil
processes that continue to modify the landscape and the habitats and ecosystems it
supports.
For a relatively small area, Scotland displays an exceptional diversity in its rocks, fossils,
landforms and soils. This diversity is a legacy of Scotland’s prolonged evolution over some 3
billion years and its position at the crossroads of colliding and rifting continents. In the
course of a journey across the face of the Earth to the southern hemisphere and back,
Scotland has been shaped by geological processes of continental drift, mountain building,
volcanism and the action of weathering, river, glacial, marine and slope processes. Evidence
for all of these is recorded in the archives of the rocks. Fossils preserved in Scotland’s rocks
provide crucial records of evolution in the plant and animal kingdoms, spanning the last 900
million years.
More recently, in geological terms, the effects of the Quaternary ice ages have left an
extensive imprint on the diversity of form of the present landscape. Patterns of glacial
erosion and deposition have fundamentally determined the physical character of the
landscape and, in many areas, the characteristics of soil parent materials; relative changes in
the levels of the land and sea and variations in sediment supply have produced a great
diversity of coastal landscapes; climate changes have been accompanied by major variations
in geomorphological processes and the types and patterns of vegetation. Although the
tempo and magnitude of physical change have reduced since the end of the last glaciation,
the geomorphological evolution of the landscape continues today, as reflected in changes at
the coastline, in river channel changes and in slope mass movements.
The soil represents the dynamic interface between physical, biological and hydrological
systems. Soils are an integral part of the landscape, reflecting not only the natural processes
through which they have been formed, but also the influences of human activities, past and
present. Soil sustains plant growth, so that terrestrial ecosystems are intimately linked to
soil conditions. Soil conditions are crucial to maintaining biological diversity in terrestrial
higher plants, and variation in vegetation distribution in habitats is intimately linked to soil
properties. Soils link the inorganic and organic components of terrestrial ecosystems and
are themselves an intimate mixture of both mineral matter and organic matter.
The purpose of this report is to highlight the nature of the Earth heritage resource, its main
components and their distributions and significance. The purpose is not to describe in detail
the geology and geomorphology of Scotland, which are covered in existing publications (e.g.
Sissons, 1967, 1976; Craig, 1991; Emeleus and Gyopari, 1992; Gordon and Sutherland, 1993;
Ballantyne and Harris, 1994; Cleal and Thomas, 1995, 1996; Gregory, 1997; Dinely and
Metcalfe, 1999; Rushton et al., 1999; Stephenson et al., 1999; Aldridge et al., 2000; Cleal et
al., 2001; Wright and Cox, 2001; May and Hansom, in press).
Page 12
10 January, 2002
In summary, the key features of our Earth heritage are:
•
•
•
•
•
the geological diversity, reflecting the length of the geological record (spanning much of
the geological timescale from the period of the oldest rocks on Earth to modern
geomorphological processes), global plate tectonics, continental drift, changing
palaeogeographies and palaeoenvironments, and geological processes such as mountain
building, volcanism and sea level change;
the rich and diverse fossil record that spans crucial moments in evolution of different life
forms;
the diversity of surface landforms and processes (geomorphological diversity), arising
from the underlying geology and pre-glacial relief, ice-age processes and environmental
change, and postglacial and contemporary geomorphological processes;
the diversity of soils, reflecting the range of parent materials and soil-forming processes;
Scotland’s role in the history of geology and geomorphology.
Page 13
10 January, 2002
2
Geology
The geology of Scotland is of national or international importance for:
•
•
•
•
•
•
•
•
•
•
•
the presence of some of the oldest rocks in the world;
rocks representative of every period in the Palaeozoic and Mesozoic;
records of palaeoenvironmental conditions, palaeogeography and structural evolution
preserved in sedimentary rock formations covering the last billion years;
understanding past geological processes (volcanism, crustal deformation) and modern
applications;
a range of igneous rocks representative of a wide range of volcanic processes ranging
from ocean floor to within plate volcanism;
sedimentary rock record produced in a wide range of sedimentary environments from
deep ocean through shallow continental shelf, deltaic and fluvial to desert and intermontane;
a range of metamorphic facies from the lowest to the highest grades;
tectonic features resulting from a variety of stress regimes from continent–continent
collision to within-plate rifting.
stratigraphic correlation;
revealing the tectonics of continental rifting, collision and mountain building
the processes of igneous activity, metamorphism and mineralisation.
Scotland’s oldest rocks date from around three billion years ago. However, most of
Scotland’s rock foundation underlying the landscape and supporting the fauna and flora, was
formed within the last billion years. For most of that time the area we know as Scotland, has
been closely associated with the edge of shifting continents or at the point where
continental splitting has occurred. The tectonic upheavals associated with the opening and
subsequent closure of the once great Iapetus Ocean and the birth and development of the
Atlantic Ocean has accounted for Scotland’s geological diversity.
2.1 The geological framework
In simple terms Scotland represents a giant geological jigsaw, essentially comprising three
large pieces: the area to the north of the Highland Boundary Fault; between the Highland
Boundary Fault and the Southern Upland Fault; and south of the Southern Upland Fault to
the Iapetus Suture (Figure 1). The areas bounded by these faults define terranes – blocks of
the Earth’s crust containing different early geological histories. A Landsat image clearly
shows the terrane boundaries, together with two other large faults – the Moine Thrust and
the Great Glen Fault – neither of which is a true terrane boundary, but both of which play
fundamental roles in influencing aspects of the natural heritage.
The jigsaw of Scotland was put together over millions of years, and only really came
together as we know it around 400 million years ago, with the joining of the Midland Valley
and the Southern Uplands to the rest of Scotland, and further south the remainder of
Britain. The history and composition of the different parts of the jigsaw, intimately related
to the birth and death of oceans, explains Scotland’s rich geological diversity and its varied
landscape, broadly reflected in the Highlands of the north, the low-lying Midland Valley and
the rolling moorland of the Southern Uplands.
Page 14
10 January, 2002
Figure 1
Simplified map of the geology of Scotland, showing the major structural features and
the distribution of the main rock groups (from Mitchell, 1997)
From 400 million years ago, younger rocks cloaked the early framework: the Devonian of
the Midland Valley, the Inverness area, Caithness, Orkney and southern Shetland; the
Carboniferous of the Midland Valley and the Tweed Basin; the Permo-Triassic sandstones of
Morayshire, Dumfriesshire and Stornoway; the Jurassic of Skye and eastern Caithness; small
pockets of Cretaceous in Morvern and Mull and the Tertiary of the Inner Hebrides (Figure
2).
Page 15
10 January, 2002
The framework is also punctured by numerous intrusions and lava flows, which bring with
them local diversity of rock type, markedly influencing topography, habitat and scenery.
These include the large granite intrusions of the Highlands – Cairngorm, Strontian, Ben
Nevis; the Devonian lava flows of the Sidlaw and Ochil Hills; the alkaline intrusions of Ben
Loyal and Loch Borrolan in the north; the Carboniferous intrusions and lavas of the Midland
Valley – Arthur’s Seat, Garleton Hills, the Midland Valley Sill; and the Tertiary Igneous
Centres of the west of Scotland – Arran, Mull, Ardnamurchan, Rum, Skye, St Kilda (Figures
1 and 2).
Scotland’s journey across the face of the Earth, the associated climatic variation and the
rock types formed through its long geological history, are summarised in Table 1.
2.1.1 Basement, Moine and Dalradian rocks
The oldest rocks in Scotland outcrop in north-western Scotland and in the Western Isles
and are called the Lewisian Gneiss. These rocks, which are some of the oldest in the world,
are about 3000 million years old and have been subjected to intense deformation and have
recrystallised from their original volcanic and sedimentary origins. For 1500 million years the
rocks were deeply buried and ‘baked’ at high temperatures deep within the crust; by 1000
million years ago they had been uplifted to form a mountain range, which now corresponds
to the area of Greenland, Canada and north-west Scotland, that was linked before the
Atlantic Ocean opened. Overlying the Lewisian in north-west Scotland is Torridonian
Sandstone, the oldest still recognisable sedimentary rock in Britain. Around 900 million
years ago, rivers draining the ancient basement rocks of Greenland brought great quantities
of sand and pebbles over the area that was to become the north-west of Scotland. The
sediment was deposited in vast alluvial fans and delta-like settings, burying the ancient
gneisses by up to 7 km. All that is left now of this huge pile of sediment is isolated hills,
notably in Assynt and the Torridon Forest.
Page 16
10 January, 2002
Figure 2
Simplified map of the geology of Scotland showing the main rock types (from Mitchell,
1997)
Page 17
10 January, 2002
Table 1
Summary of the geological evolution of Scotland
Event
Geological Period
Where in the
World?
Climate
Environment
Ice ages
Quaternary
2.5 million years ago to
the present day
57° N
Major cooling
of climate to
glacial–interglacial
conditions
Opening of
the North
Atlantic
Tertiary
2.5 – 65 million years
ago
50° N
Sub-tropical:
warm and
humid
Cretaceous
145–65 million years
ago
Drifted from
40° to 45° N
Warm
Repeated growth and
decay of ice sheets and
mountain glaciers.
Formation of landforms
of glacial erosion and
glacial and glaciofluvial
deposits. Last glaciers in
Scotland during Loch
Lomond Readvance
(12,500–11,000 years
ago).
Large volcanoes develop
in western Scotland –
Mull; Ardnamurchan;
Rum; Skye; St Kilda –
erupting ash and lava.
Fissure dykes, such as
present-day Iceland,
generate large amounts
of lava. Some sediments,
deposited by streams
and carrying boulders off
the rapidly eroding
volcanoes and remains
(e.g. leaves and stems) of
trees and plants growing
on and around the
volcanoes, accumulate
between lava flows.
Scotland is
predominantly an upland
area. Initially, it is flanked
by sea to the east in the
Moray Firth, but the
coast to the west lies
beyond the Outer
Hebrides. Later, the area
of sea increased to
cover parts of the west
coast of Scotland. Some
white shoreline sands
were deposited, and
later some chalk.
Page 18
10 January, 2002
Page 19
Jurassic
210–145 million years
ago
Moved from
40° to 45° N
Sub-tropical:
warm, fairly
humid
Triassic
245–210 million years
ago
Moved from
15° to 35° N
Hot, semiarid, becoming
less arid later
Permian
290–245 million years
ago
Moved from
10° N to 25° N
Hot, arid
becoming
semi-arid later
Most of Shetland, the
Outer Hebrides and
northern and eastern
Scotland form upland
areas that supply
deposits into deltas and
shallow marine seas.
Reef corals develop in
warm waters, and shelly
creatures, such as
brachiopods, bivalves,
ammonites and seaurchins, thrive in the sea.
Dinosaurs and swimming
reptiles are also present.
Continental-type
environment, becoming
marine later in the west
of Scotland. Reptiles live
near Lossiemouth
around pools of fresh to
brackish water that dries
up from time to time.
There are areas of
floodplains with
intermittent streams.
Desert conditions
prevail, similar to today’s
Arizona deserts. There
are bare rocky hills, and
mesas and buttes.
Volcanoes are erupting
in the Midland Valley.
Reptiles and a few
desert plants exist. The
Highland’s are eroding,
and large amounts of
deposits are building out
where the mountains
meet the plains. Areas of
windblown sand are
surrounded by higher
land, which supplies
more deposits to
occasional streams.
Later, Scotland is flanked
to the east by the
Zechstein Sea, which
occasionally dries up and
forms salt deposits.
10 January, 2002
The Iapetus
Ocean
closes and
the
Caledonian
Mountains
form
Page 20
Carboniferous
360–290 million years
ago
Travelled
across the
equator, from
5° S to 15° N
Hot, arid to
semi-arid,
becoming
tropical, very
humid and
monsoonal
with high
humidity,
returning to
semi-arid
conditions
later
Devonian
408–360 million years
ago
Starting around
10° S and
moved
gradually north
to 5° S
Warm to hot,
mostly semiarid,
sometimes
arid, with
occasional
downpours
Silurian
440–408 million years
ago
Started at 15° S
and moved to
around 12° S
Hot start
becoming
warm later
A mixture of rivers,
deltas, swamps, shallow
seas, lagoons and
occasional salt-flats. The
swamps gave rise to the
present-day coal fields.
Lavas occur in the Clyde
and Forth areas, and
active volcanoes exist
throughout the Midland
Valley, (e.g. Arthur’s Seat
in Edinburgh) the
Highlands and the
Southern Uplands are
above sea level. The first
reptile makes its
appearance near
Bathgate.
A land-locked desert,
the nearest sea being
located in what is now
the southern North Sea.
A huge inland lake
covers the Caithness,
Orkney and Shetland
area and extends
eastwards to Norway.
Sediments are
transported in rivers and
deposited in fans where
mountains meet the
plains. Some lakes occur
containing fish.
Volcanoes are active.
Primitive plants and
arthropods represent
one of the world’s first
terrestrial ecosystems
around hot volcanic
springs at Rhynie, in
north-east Scotland.
Northern Scotland,
north of the Highland
Boundary Fault, remains
above sea level.
Sediments continue to
build up in the trench
area and eventually
become exposed to the
air. Sands and muds,
some containing the
remains of fish, are
deposited in the sea
10 January, 2002
Ordovician
490–440 million years
ago
Moved from
30° S to 15°S
Hot, turning
warm later
The Iapetus
Ocean
opens
Cambrian
543–490 million years
ago
25° S to 30° S
Tropical,
warm and
humid
Before the
Iapetus
Ocean
develops
PreDalradian
cambrian
pre-543
million
years ago
Started north
of the equator
then crossed it
and moved
south later
Warm and
humid
Torridonian
Page 21
occupying part of the
Midland Valley area.
Limestones develop in
the warm shallow seas
of north-west Scotland.
A series of volcanoes
develops in the Iapetus
Ocean, just south of the
edge of the continent.
North of the volcanoes
is a deep basin,
containing muds and
volcanic rocks. South of
the volcanoes, sediments
accumulate in the trench
area formed by the
subduction of the
Iapetus Ocean crust
beneath the edge of
continent Laurentia;
today, these sediments
form the Southern
Uplands.
Shallow marine
conditions give rise to
sandy shelf deposits. The
sea becomes deeper and
muds are deposited.
Finally, it shallows again,
and limestones form in
the warm waters.
Shallow to deep marine
basin deposition occurs.
This is accompanied by
volcanic activity as the
crust is stretched and
thinned. Great ice ages
scour the adjacent lands
and glacial debris is
deposited in the marine
environment.
Large meandering
braided rivers flow
across a wide flat plain.
The rivers are depositing
sands on top of the old
Lewisian landscape. The
rivers are quite shallow,
perhaps 7 m at their
deepest, but wide, some
over 1 km and perhaps
up to 500 km in length.
The banks of the rivers
10 January, 2002
Moine
Some
rocks
dating
back to 3
billion
years
Lewisian
are unstable, since there
is no vegetation at this
time to hold the
sediment together. The
sand is being eroded
from mountains far to
the north-west, perhaps
in Greenland, or beyond
in present-day Canada.
Shallow marine deposits
of sand and muds
accumulate on the
eroded Lewisian
Gneisses.
Volcanic rocks and their
igneous equivalents form
the crust of a young
planet Earth. The
erosion of the volcanics
provides sediment
deposited in low-lying
areas and seas, affected
by tidal forces much
greater than the present
day, owing to the Moon
being thousands of
kilometres closer to the
Earth.
Occupying the bulk of the Scottish Highlands, to the south and east of the Torridonian
Sandstone, are large outcrops of Moinian and Dalradian metamorphic rocks. Around 800
million years ago, this area was a basin on a newly formed Iapetus Ocean into which rivertransported sediments were poured and deposited continuously for around 500 million
years. This produced sediments 25 km thick on the subsiding ocean floor. The older
Moinian rocks are largely grey, flaggy schists, whereas the younger and more varied
Dalradian consist of schists, phyllites, slates, limestones and volcanic rocks. Within the
Dalradian succession on Islay a ‘fossil’ glacial deposit provides evidence of great ice sheets
that once covered Scotland 670 million years ago, 30° south of the equator. Trace fossils
found within the Dalradian succession of Islay represent some of the oldest evidence of
complex multicellular life.
2.1.2 Caledonian mountain building: the coming together of Scotland
Around 500 million years ago the building of the Caledonian mountains began; two crustal
plates, one comprising much of what is now northern North America and northern Europe,
collided to close the Iapetus Ocean. The Moinian and Dalradian sediments that had
accumulated in the ocean were recrystallised and intensely deformed, producing folds,
during a process called regional metamorphism, which converted the sedimentary rocks,
mainly shales and sandstones, into the hard, schists and slates we see today. The pile of
sedimentary rock being affected was considerable, with the most intense metamorphism
occurring many kilometres deep within the crust. The occurrence of these metamorphic
Page 22
10 January, 2002
rocks at the Earth’s surface is testimony to the erosional processes over many millions of
years since the formation of the Caledonian mountains.
The crustal collision was so intense that the Dalradian rocks in the Grampians were arched
up and over-folded, producing a huge recumbent fold, termed a nappe, that stretches from
Aberdeen to Ireland. A similar nappe in the northern Grampians involved both Moine and
Dalradian, the two nappes being separated by a large thrust fault, called a slide, above which
enormous slabs of rock were laterally transported. In north-west Scotland a telescoping
effect occurred, with the formation of a world-renowned fault known as the Moine Thrust.
This telescoping of the Moine succession represented an actual shortening of the crust by
many miles. Whole masses of rock were thus lifted upward and thrust forward, placing
older rocks above younger ones. This is evident at places such as Loch Glencoul, where,
separated by a thrust fault, Lewisian Gneiss rests upon Cambrian sediments.
As the continental plates carrying North America and northern Europe converged, the
oldest and coolest portions of the Iapetus Ocean floor sunk beneath the advancing Scottish
foreland in a process called subduction. The sediments which had accumulated over
southern Scotland were lifted and bulldozed to form the Southern Uplands. Evidence of the
break-up of the ocean floor can be seen between Girvan and Ballantrae, where unmistakably
marine sedimentary rocks and erupted underwater pillow lavas are well exposed. The
ancient ocean floor sedimentary rocks yield fossils that have provided critical dating for
these events. Elsewhere, in the Grampians the intensity of the deformation and
metamorphism have, apart form the fossil-bearing rocks of Islay, precluded the survival of
any fossil evidence. Across the Caledonian Mountain chain, which would have been alpine in
scale, masses of molten rock, derived from melting of rock deep in the crust, rose upward
through the crust and cooled to form granite. Now exposed, these rock masses form the
range of familiar and diverse Scottish granites from Aberdeen and Peterhead through the
Cairngorms to Rannoch Moor, Etive, Strontian and the Ross of Mull.
2.1.3 Devonian and Carboniferous
The tectonic upheavals that brought together the foundations of Scotland ended around 400
million years ago at the start of the Devonian, a period in time quite often referred to as the
Old Red Sandstone. Scotland now formed a mountainous land in a vast super-continent that
comprised northern Europe and much of North America. Landlocked and far from the
nearest ocean, Scotland lay 20° south of the equator and had a hot, semi-arid climate. As a
consequence of the Caledonian crustal collision, major faults developed in Scotland,
principally the Great Glen, Highland Boundary and Southern Upland Faults, the last two
being the bounding faults of a large rift valley which formed in the Midland Valley of central
Scotland. Under the arid environmental conditions, the Caledonian Mountains were
subjected to erosion, with rivers transporting and depositing the resulting sediment load
into mountain-girt basins and adjacent low-lying areas, mainly the Midland Valley and the
area we know now as the Moray Firth. In the Midland Valley total sediment accumulation
eventually amounted to some 10 km over a period of around 50 million years. In the Moray
Firth, Caithness and Orkney areas, coarse-grained deposits were deposited around the
edges of a vast inland lake, the Orcadian Basin Lake, while fine-grained deposits were
deposited at its centre, giving rise to the famous Caithness flagstone. In a few places erosion
has revealed the unconformable contact of the Devonian deposits with older foundation
rocks, such as the Dalradian schists on Arran and the Silurian deposits at Siccar Point,
Berwickshire, both incidentally discovered and described by James Hutton.
Page 23
10 January, 2002
The Orcadian lake supported a rich and diverse fish fauna, which Hugh Miller discovered
and described. Around the basin and further afield, primitive plants had colonised the land.
At Rhynie in Aberdeenshire a diverse community of early plants and land-living arthropods
thrived around a hot-spring environment. Fossil evidence of this earliest wetland ecosystem
are perfectly preserved in the silica, or chert, deposits from the hot springs. The volcanic
activity at Rhynie was part of much more widespread activity, principally in the Midland
Valley (e.g. Pentland Hills and Ochils) and in the Glen Coe/Oban area, where there are
extensive lava flows.
The Carboniferous Period followed from the Devonian, and sediment deposition was
almost entirely confined to the Midland Valley. With Scotland moving over the equator
during the Carboniferous 360–300 million years ago, most of the sediment deposition took
place under tropical conditions. Early on in the period, there was substantial volcanic activity
in the Midland Valley, from Kintyre in the west to Edinburgh in the east. As volcanic activity
waned, warm tropical seas repeatedly flooded the valley bringing about the deposition of
limestones. A rich fauna inhabited the sea and coastal lagoons giving rise to a spectacular
and varied fossil fauna. Whenever the sea abated, huge quantities of sand and mud were
deposited by rivers that flowed across the low-lying coastal and lagoon landscape. In these
environmental conditions forested tropical swamps carpeted the landscape and gave rise
eventually to coal, sandwiched between great thickness of sandstone and shale. At the end
of the Carboniferous new tectonic upheavals, this time concentrated far to the south in
what is now northern France, caused the folding of the Scottish Carboniferous sedimentary
sequences into the separate basins we see today.
2.1.4 Permian to the Tertiary
By the beginning of the Permian period, Scotland had drifted north, crossing the equator
into dry, arid belts. Sedimentary rocks produced at this time, and subsequently during the
Triassic period, are sometimes referred to as the New Red Sandstone to distinguish them
from the Old, because, similar to the Old, they are in part dune-bedded, windblown
sandstones. Permian and Triassic rocks are exposed in many low-lying areas of Scotland,
primarily in west central Ayrshire, on Arran and in the Elgin area. However, these deposits
are at their most widespread under the sea in the Clyde estuary, around the coasts of west
Scotland and beneath the North Sea. These areas, now occupied by the sea, were terrestrial
basins in which sediment accumulated during Permian and Triassic times between 290 and
210 million years ago. Indeed, from Permian to Tertiary times the sedimentary rock layer
succession in the North Sea is complete and provides the geological framework for North
Sea oil and gas reserves.
In and around the Hebrides, on the isles of Skye, Raasay, Eigg and Mull, on the mainland in
Morvern and on Arran, there are sedimentary rock sequences from Jurassic and Cretaceous
times. These sequences provide evidence of warm, shallow seas that fringed an early
Scottish landmass. The fossil faunas allow correlation with marine conditions over what is
now northern Ireland and much of England.
It was during Jurassic times that the continental landmass that encompassed America and
Europe began to split, and movements of the plates shifted Scotland further north. At the
start of the Tertiary Period about 60 million years ago, fractures in the crust associated with
the formation of the North Atlantic Ocean opened up along the western side of Scotland.
This resulted in major volcanic activity which lasted for a few million years. Initially, huge
Page 24
10 January, 2002
volumes of basalt lava poured from the fissures, building a substantial lava plateau around 4
km thick. Subsequently, the fissure style of eruption gave way to the development of several
major volcanic centres, from St Kilda in the north to Skye, Ardnamurchan, Rum, Mull to
Arran in the south, along a NW–SE trending line. The lavas have left a legacy of ‘trap’
landscapes on Skye and Mull. Remains of the large volcanic cones and calderas that formed
the central volcanic complexes are evident on Mull and Skye and Arran, but the principal
remains of the volcanic activity are the granites and gabbros forming the mountains of Skye,
Rum, Mull and Ardnamurchan. These rocks represent the magma chambers and internal
plumbing of once great volcanoes, now severely eroded after 55 million years of weathering.
2.2 Understanding the Earth: Scotland’s geology in a
worldwide context
Scotland’s rocks constitute a key resource of national and international importance for
studies in metamorphic, structural and volcanic processes worldwide, in addition to the
insight they provide into ancient geographies and environments. Many elements of Scottish
geology have provided crucial evidence for past geological processes and allowed modern
applications. A simple good example would be the eroded remains of Arthur’s Seat, which
can allow conclusions to be drawn about the internal plumbing of modern volcanoes such as
Vesuvius
2.2.1 Ancient geographies and environments
Scotland’s geological heritage over the past billion years provides an overview of the past
geographies and environments that existed while the crustal components which make up
the country moved over the face of the Earth. The information provided by the geological
record of deep ocean environments, shallow marine seas and arid desert adds to the global
picture of environmental and geographic change over millions of years.
2.2.2 Stratigraphic correlation
Through the correlation of rock types, much of Scotland’s geological heritage can be
dovetailed with the global picture. In many instances Scotland has formed a key part in
elucidating particular aspects of Earth history. For example, the ancient Lewisian Gneisses of
the far north-west and the Outer Hebrides have affinities with similar areas of ancient rock
in Greenland and North America, illustrating that these areas were once part of the same
continental landmass. Changes through time in fossil populations in Ordovician and Silurian
rocks of the Southern Uplands provide evidence for, and document, the closure of the
Iapetus Ocean. Indeed, the completeness of the sedimentological record spanning the
Ordovician and Silurian periods that exists in the Southern Uplands has led to the
designation of the internationally agreed boundary being defined at Dob’s Linn. This
boundary stratotype, defining the junction between the Ordovician and Silurian periods, is
used as the reference point for this stratigraphic boundary worldwide.
Jurassic age rocks along the fringes of eastern Scotland, which share affinities with those in
eastern and southern England and further afield in Europe and which bear testimony to
shallow, tropical seas during the Mesozoic, are another illustration of Scottish geology
extending beyond our shores and contributing to the global geological picture.
Page 25
10 January, 2002
2.2.3 Structural geology and metamorphism
Fossil evidence has been crucial in determining the existence of the Iapetus Ocean, and
therefore has a direct bearing on global tectonics. However, in complex geological terranes
where there is no fossil evidence, structural analysis and geochemistry are brought to bear
on the geological record. An understanding of the geologically complex Grampian mountains
in the early part of the twentieth century by geologists such as Bailey, Clough, Shackleton
and Barrow laid much of the groundwork for understanding the structurally complex
terranes worldwide. The same can be said for the elucidation of the structurally complex
Moine Thrust Zone, the most famous of the major Caledonian structures. Research based
on the early twentieth-century work of Peach and Horne in this area paved the way for
understanding large-scale, higher-level crustal deformation, not only in Scotland but across
the world. Other worldwide applications of research on Scottish geology include the
unravelling the Lewisian Complex by Janet Watson, which laid much of the groundwork for
understanding the geological history of poly-deformed gneissic terranes.
2.2.4 Igneous processes and petrology
Areas of classic volcanic geology, such as Glen Coe, Rum and Arthur’s Seat, have all
provided crucial evidence for past geological processes and allowed modern applications
worldwide. Geological mapping of the Glen Coe area, early in the twentieth century,
revealed volcanic rocks of Devonian age attributable to cauldron subsidence, the first
example of this type of volcanicity to be identified and described in the geological record.
The Tertiary volcanic geology of Rum has yielded much information on the processes taking
place in the environment of the magma chamber, with the development of theories relating
to the origin of layering in igneous rocks. The Arthur’s Seat volcanic complex in Edinburgh
provided key evidence supporting the theories of James Hutton, which laid the foundations
for the development of modern geology. Arthur’s Seat is still regarded as perhaps the best
example on Earth of a dissected ancient volcanic cone.
A further measure of the importance of Scottish geology in the development of igneous
petrology may be appreciated from the number of rock types that were first discovered and
described in this country. Kentallenite, lugarite, craignureite and mugearite are all examples
of rock types first discovered in Scotland and named after the location of their discovery.
For example, Mugearite is named after a croft on Skye.
2.2.5 Mineralogy
Scotland’s role in mineralogical science has been a significant one, with many mineral species
having been first discovered in Scotland, including strontianite, mullite and leadhillsite.
Page 26
10 January, 2002
3
Palaeontology
The palaeontology of Scotland is of national or international importance for:
•
•
•
•
understanding the evolution of many animal and plant groups;
dating rock sequences and making possible correlation with rock sequences worldwide;
constraining tectonic models;
the development of palaeogeographic, palaeoenvironmental and palaeoecological models
stretching back more than 600 million years.
Scotland is of great importance in the history and development of palaeontology. Although
more than half of the Scotland’s area is underlain by igneous and metamorphic rocks, the
remaining sedimentary rocks, especially the Palaeozoic and Jurassic sequences, contain rich
fossil assemblages of immense diversity, some of which are unique. It is no exaggeration to
say that some of Scotland’s fossils – vertebrate, invertebrate, plant and trace – have been
critical for the development of many fields in palaeontology. The variety and richness of the
fossil heritage reflects the many biofacies and types of preservation that have arisen during
the country’s long and varied geological history.
3.1 Key elements of Scottish palaeontology
Some significant elements of the fossil heritage are outlined below, arranged by system.
3.1.1 Precambrian
Fine-grained Torridonian Sandstone sediments of Precambrian age, found at Cailleach Head,
on Little Loch Broom, have yielded the remains of 800- to 900-million-year-old microfossils. These are simple aquatic organisms, such as filamentous cyanobacteria, and are the
oldest fossils in Britain.
Uniquely unmetamorphosed 600-million-year-old silty sedimentary rocks of the Bonahaven
Formation within the Dalradian Supergroup of Islay have yielded the traces of the world’s
oldest known complex organism, a worm-like creature, Neonereites uniserialis.
3.1.2 Cambrian–Ordovician
Lower Palaeozoic rocks are largely confined to central and southern Scotland, the exception
being the Cambro-Ordovician sequence of the Northwest Highlands. It was the discovery of
the Lower Cambrian olenellid trilobites in this sequence, by Ben Peach in the 1880s, that led
to the recognition of Northwest Scotland’s North American affinities and which ultimately
led in part to the development of modern palaeogeographic models.
3.1.3 Ordovician–Silurian
Charles Lapworth working in the last quarter of the nineteenth century was the first to
utilise graptolites as biostratigraphical indicators. Lapworth’s meticulous work on the
graptolite assemblages led to the unravelling of the complex structure of the Southern
Uplands and is the basis upon which the modern palaeogeographic and tectonic models of
the area are based.
Page 27
10 January, 2002
3.1.4 Silurian
The chain of Silurian inliers along the southern edge of the Midland Valley, stretching from
Girvan to the Pentland Hills, is composed mainly of shallow-water sediments, yielding
unusual fossil assemblages. The early jawless fish Jamoytius kerwoodi, found within the
Lesmahagow inlier, represents the world’s oldest known vertebrate.
3.1.5 Devonian
The Devonian or Old Red Sandstone in Scotland is entirely fluviatile–continental and
lacustrine in origin. This system is famous for the fish faunas of the Orcadian Basin and the
Midland Valley. Achanarras in Caithness and Turin Hill in Angus are world-renowned sites
for their fossils. The faunas, which contain armoured and jawless groups in addition to the
forerunners of today’s bony fish, have allowed biostratigraphical links to be established with
other areas in northern Europe and North America. The Lower Devonian Rhynie Chert in
Aberdeenshire is a unique deposit that represents the perfect three-dimensional
preservation in chert of the world’s oldest known terrestrial ecosystem, complete with
fauna and flora. Thought to be the remains of a wetland environment associated with a
centre of fumerolic activity, the chert has yielded some of the oldest vascular plants, the
earliest evidence of plant–animal interactions and the oldest known insect. Younger
Devonian deposits, at Scaat Craig near Elgin and at Tarbat Ness on the east coast, have
yielded some of the world’s oldest amphibian remains and traces.
3.1.6 Carboniferous
The Lower Carboniferous sediments of the Midland Valley and the northern edge of the
Northumberland Trough stand apart lithologically and faunally from the thick marine
limestones and shales further south. They display a very broad range of facies, shallow
marine, estuarine–deltaic, lagoonal and freshwater, which are the source of rich and often
unusual faunas. At East Kirkton near Bathgate, for example, the remains of the world’s
oldest known reptile, Lizzie, were discovered, along with numerous amphibian and other
reptile-like creatures. Also in the east, close to Edinburgh, the world’s first ‘conodont
animal’ was discovered. Conodonts are tiny fossils; their geological record dates back to the
Cambrian period. They have been used extensively worldwide over many years for the
dating and correlation of sedimentary sequences. Despite their usefulness, the nature of
these important fossils remained enigmatic. However, the discovery of conodonts forming
the mouthparts of a tiny eel-like animal in rocks at Wardie on the Firth of Forth finally
proved the nature of the fossils. In the west, a magnificently preserved biota of fish and
crustaceans, including some unique sharks, has been discovered at Bearsden near Glasgow.
The Scottish Carboniferous also contains the spectacular fossil trackways of giant 2-m-long
myriapods that once lived in the coal forests, the example at Laggan on Arran being of
particular significance. The fossil plants of the Scottish Carboniferous are abundant and well
preserved. They are often found as compressions and as permineralisations with threedimensional detail. The floras of the Pettycur Limestone in Fife, for example, have yielded
exquisite three-dimensional material. In Victoria Park in Glasgow there are internal moulds
of 11 Lycopod or Scale Tree stumps in growth position, which provide an important
palaeoenvironmental indicator.
Page 28
10 January, 2002
3.1.
Permian–Triassic
The Triassic rocks of Elgin, at the margins of the North Sea basin, have yielded a rich fauna
of reptiles belonging to 11 or so genera, ranging from 20-cm-long sphenodonts to large
mammal-like reptiles and possibly a single genus of dinosaur. In addition to body fossils, the
Permo-Triassic sequence has yielded numerous tracks and traces. The fauna has provided
biostratigraphic links with places as far away as South Africa and allowed the construction of
fairly detailed palaeoecological models.
3.1.8 Jurassic
The on-land exposures of Jurassic rocks in Scotland are tiny in relation to the sequences of
the previous systems. However, they are of major significance in helping to elucidate the
geology of the North Sea. Jurassic-age sediments in the Hebrides were noted as long ago as
1819 by John MacCulloch and yielded Hugh Miller’s first fossils in the east of the country.
Ammonite fossils have been invaluable in zoning Scotland’s Jurassic sequences and
correlating them with the rest of the world. The Middle Jurassic rocks of Skye and Eigg have
yielded large vertebrate fossils, including the remains of herbivorous and carnivorous
dinosaurs and their tracks. Some of the world’s earliest mammal fossils have been found in
association with dinosaur-bearing strata on Skye.
3.1.9 Tertiary
At Ardtun in western Mull, there are the fossil remains of an early Tertiary, or Palaeocene,
flora that existed between sporadic outbursts of lava and ash at the onset of Greenland’s
separation from northwest Europe. The flora, mainly in the form of leaves and twigs found
within inter-basaltic silts and clays, consists of oak, hazel, maidenhair and magnolia trees.
Close by, at Ardmeanach, is MacCulloch’s Tree, the remains of a still vertical, 12-m-high and
2-m-wide tree that was overwhelmed by lava.
Page 29
10 January, 2002
4
Geomorphology
The resource of geomorphological and Quaternary interests is remarkable for its diversity,
which encompasses glacial, periglacial, coastal, fluvial and lacustrine systems. The principal
components of these systems comprise relict landforms and sediments, active Earth surface
processes and sedimentary records of Quaternary landscape evolution and environmental
change preserved in a range of terrestrial, lacustrine and marine deposits. Change, both
geographically and through time, and the factors that determine its inception, magnitude,
direction and effects are fundamental aspects of the interest in the resource.
4.1 Pre-glacial landforms
These pre-glacial features are of national or international importance for:
•
•
•
•
the information which they provide on long-term landscape and landform evolution;
their juxtaposition with glacial landforms (e.g. in NE Scotland and the Cairngorms),
indicating spatial variations in the intensity of glacial erosion;
the diversity which they add to the geomorphology of Scotland;
the diversity they add to the landscape and habitats in terms of large-scale topographic
units (e.g. basins and hills reflecting differential weathering of different rock types; large
scarps, inselbergs) and in terms of small-scale landforms (e.g. tors).
The rocks formed before 2.5 million years ago determine the pre-glacial topography and
materials on which Quaternary glaciations (and other processes) have operated. Although
Scotland is particularly noted for its glacial landforms, a number of key elements in the
landscape have survived from pre-glacial times, although they were modified to varying
extents by subsequent glaciations (Hall, 1991).
Erosion surfaces are evident in the landscapes of much of Scotland. They are particularly
dominant in eastern and southern areas, especially in the uplands, where they form
extensive surfaces. In the west, where dissection and glacial erosion have been more
intense, they are more apparent as summit accordances. In NE Scotland a series of stepped
surfaces extends from the coast to the high plateaux of the Cairngorms (Figure 3a).
Scarps occurring as long, straight, steep slopes front many mountain massifs in Scotland. In
some cases these are fault scarps, as in the case of the Highland edge in Angus and the
Mearns, and along the front of the Ochils east of Stirling. In others, they represent slope
retreat, as in the Torridonian sandstone mountains north of Ullapool (Figure 3b).
Valleys and drainage patterns that include remnants of Tertiary drainage systems are
preserved in the present landscape. Among the best examples are the eastward-draining
rivers in the eastern Highlands and the upper basin of the River Clyde (Figure 3c).
Page 30
10 January, 2002
Figure 3a
Elements of the pre-Quaternary geomorphology of Scotland: erosion surfaces in NE
Scotland (from Hall, 1991). (Reproduced by permission of the Royal Society of
Edinburgh and A.M. Hall from Transactions of the Royal Society of Edinburgh: Earth
Sciences, volume 82 (1991), pp. 1–26.)
Topographic basins are a widespread feature of the landscape of the Highlands, often strung
out along the river courses (e.g. along the Dee and Don) like beads on a string (Figure 3d).
Many of these basins have been infilled by glacial and postglacial deposits and can be
described by the term alluvial basin. Some have been scoured by glacial erosion (Rannoch
Moor); some have been exhumed from beneath a cover of Devonian sediments (e.g.
Cabrach). Modern rivers flowing within these relatively flat basins in the uplands can adopt
planforms more usually seen in lowland rivers (e.g. on parts of the River Don).
Inselbergs are isolated hills, often developed on more resistant rocks (e.g. Schiehallion,
Culbin Hill, Mormond Hill). Others are the result of parallel scarp retreat and dissection (as
in the Torridonian sandstone mountains north of Ullapool) (Figure 3d).
Tors are particularly well developed on the hill summits and higher flanks of the granites of
eastern Scotland (e.g. Cairngorms, Bennachie). Some of the larger features probably have a
long and complex evolution of weathering and stripping during the Tertiary and Quaternary.
Many appear to have survived glaciation and may be indicators of the presence of cold-based
ice sheets.
Page 31
10 January, 2002
Figure 3b
Page 32
Elements of the pre-Quaternary geomorphology of Scotland: features associated with
early Tertiary uplift (from Hall, 1991). (Reproduced by permission of the Royal Society
of Edinburgh and A.M. Hall from Transactions of the Royal Society of Edinburgh: Earth
Sciences, volume 82 (1991), pp. 1–26.)
10 January, 2002
Figure 3c
Elements of the pre-Quaternary geomorphology of Scotland: Late Tertiary drainage
pattern (from Hall, 1991). (Reproduced by permission of the Royal Society of
Edinburgh and A.M. Hall from Transactions of the Royal Society of Edinburgh: Earth
Sciences, volume 82 (1991), pp. 1–26.)
Deeply weathered bedrock is an important geomorphological relic from the Tertiary Period. It
is believed to have formed under humid tropical and sub-tropical conditions. Remnants of
such weathering are most extensive in NE Scotland, particularly in Buchan, reflecting the
tectonic stability of the area and the low intensity of glacial erosion. Isolated pockets occur
in the west but may be associated with places that have hydrothermal alteration.
Page 33
10 January, 2002
Figure 3d
Page 34
Elements of the pre-Quaternary geomorphology of Scotland: distribution of basins and
inselbergs in the Scottish Highlands (from Hall, 1991). (Reproduced by permission of
the Royal Society of Edinburgh and A.M. Hall from Transactions of the Royal Society of
Edinburgh: Earth Sciences, volume 82 (1991), pp. 1–26.)
10 January, 2002
4.2 Quaternary landforms and deposits
Quaternary landforms and deposits are of wider national or international significance in
several respects:
•
•
•
•
•
•
•
•
•
by virtue of their spatial location on the maritime fringe of western Europe, providing a
link between the North Atlantic and continental Europe and providing a record of
terrestrial environmental, ecosystem and glacier responses to changes in North Atlantic
circulation;
the availability of litho- and biostratigraphic records for critical time periods of rapid
environmental change, which are susceptible to the application of new analytical
approaches and techniques, and that allow correlation of the terrestrial stratigraphic
records with the offshore records and ice-sheet cores;
in field and theoretical knowledge of the behaviour of glaciers, allowing the development
and application of mathematical models of former maritime ice sheets and their
application to explain the patterns and processes of landform and landscape genesis and
to develop and test palaeoclimate reconstructions; this applies, for example, to models
of glacial erosion based on the diversity of landscape types (areal scouring, selective
linear erosion, areas of minimal erosion) and the Loch Lomond Stadial icefield in the
west Highlands;
for the development of new models describing the form, extent and response of the last
ice sheet, based on offshore mapping, mathematical modelling and the palaeoclimate
results from the Greenland ice-sheet cores and North Atlantic Ocean cores;
improved understanding of the processes of formation of glacial and periglacial
landforms and deposits, e.g. through the access provided to the bed landforms of a
former mid-latitude ice sheet;
improved palaeoenvironmental reconstructions based on multi-proxy data for
terrestrial, offshore and nearshore marine environments;
geomorphological and palaeoenvironmental changes associated with the interplay of
isostatic and eustatic changes; crustal rheology;
the diversity of classic glacial and periglacial landforms and landscapes in a relatively
compact geographical area;
baselines for environmental monitoring.
Although the broad outlines of the Scottish landscape owe much to long-term geological
and tectonic controls, the finer details reflect the imprint of successive ice ages. The
Quaternary includes the last 2.5 million years. It is often used synonymously with the term
Ice Age, but the Quaternary is characterised by many fluctuations in climatic conditions,
with as many as 50 major cold (glacial) and warm (interglacial) oscillations recognised.
Environmental change, and the dramatic shifts in geomorphological processes that
accompanied them, is therefore a fundamental feature of the Quaternary. Particular types of
environmental change have left a strong imprint in the landforms, fossils and recent
sedimentary deposits of Scotland (Table 2). As the glaciers advanced and retreated, their
interaction with the variable geology and pre-existing relief have produced the striking
diversity of the present landscape. Processes of glacial erosion remodelled the landscape, and
glacial deposition left a characteristic signature on the lowlands and in many upland valleys.
During the melting of the great ice sheets, the liberation of vast volumes of meltwater
produced an equally characteristic suite of waterlain glaciofluvial landforms and deposits. In the
areas that lay beyond the glaciers, and also during less severe cold stages when glaciers were
either restricted in their distribution or absent altogether, periglacial conditions prevailed.
Page 35
10 January, 2002
These are characterised by frost-assisted processes and by a range of frost- and ground-icegenerated landforms and deposits. Mass wasting (downslope movement of soil on both large
and small scales) and increased wind action were prevalent and also produced a range of
diagnostic features. Beyond the ice limits, major shifts in coastline position occurred, river
regimes and baselines altered and vegetation cover varied.
Changes in river courses and channel patterns have followed from changes in discharge,
sediment supply and sea level. There have been times when rivers built up large thickness of
glacially derived debris on their floodplains; others when they eroded into their floodplains.
The resulting effects on the landscape are staircases of terraces in many river valleys.
Change through time is a fundamental aspect of the Quaternary. Very often traces of
successive environments are recorded in layers of sediment preserved on top of one
another, e.g. glacial deposits may overlie interglacial beach deposits and in turn be
succeeded by periglacial slope deposits and later sand dunes. Sites with such sequences can
provide particularly revealing perspectives on the Quaternary. Change too is apparent in the
present landscape on river floodplains, along the coast and on hill slopes as
geomorphological systems respond to perturbations of varying magnitude and frequency.
Quaternary environmental changes and associated processes have not been uniform in their
operation throughout Scotland, but have reflected the varied geology, pre-glacial relief and
climate gradients, and this has produced a remarkable regional diversity in surface landforms
and deposits.
Page 36
10 January, 2002
Age
(ka BP)
Oxygen
Isotope
Stage
Chronostratigraphy
Main glacial events and landscape changes
• vegetation and soil development; human
impacts; river channel changes; sealevel changes
Holocene
10
1
11
Lateglacial
12
13
Late
Devensian
Loch Lomond
Stadial
• mountain glaciation ; periglacial activity
down to sea level; changes in relative
sea level; vegetation revertence
Late-glacial
(Windermere)
Interstadial
• development of soils and pioneer
vegetation
2
Dimlington Stadial
24
• last ice sheet glaciation extending into
North Sea and on to West Shetland and
Hebrides shelves
n
30
40
3
50
59
D e v e n s i a
late Quaternary
26
• fluctuating mountain glaciers and
ice fields
Middle
Devensian
• (?) ice sheet advance before c.35ka
BP
• ice sheet glaciation extending west of
the Hebrides and Shetland and in Outer
Moray Firth
4
71
5a
85
5b
Brimpton Interstadial
Early
Devensian
92
5c
Chelford Interstadial
• pine and birch woodland in NE
Scotland and heath and grassland
on Shetland during interstadials
105
5d
116
5e
Ipswichian
128
• last interglacial; pine woodland on
Shetland
• extensive ice sheet glaciation in North
Sea and West Shetland and Hebrides
(?) shelves
6
186
7
245
• sequence of glacial and
middle Quaternary
8
interglacial stages; no clear
303
evidence preserved
9
339
10
362
11
• interglacial deposits in North Sea
423
12
Anglian
13-19
Cromerian ‘complex ’
480
early
Quaternary
780
20 -
• extensive ice sheet glaciation in North
Sea and on Hebrides and West
Shetland shelves
• sequence of glacial and
interglacial stages
• ice sheet in Forth Approaches
and North Sea
• early Quaternary mountain glaciations
• initiation of glacial erosion
2400
Table 2
Page 37
Summary of main glacial events and landscape changes during the Quaternary in
Scotland. Note that the timescale shown is not linear
10 January, 2002
4.2.1 Landforms of glacial and meltwater erosion
The landforms and landscapes of glacial and meltwater erosion are of national or
international importance for:
•
•
•
•
•
the information which they provide on long-term landscape and landform evolution;
the spatial variations in the intensity of glacial erosion which they demonstrate, indicating
variations in ice-sheet properties and processes;
for the information which they provide for testing models of ice-sheet dynamics;
the diversity which they add to the geomorphology of Scotland;
the diversity they add to the landscape and habitats in terms of large-scale topographic
units (e.g. the cliff forms of corries and troughs) and in terms of small-scale landforms
(e.g. crag and tail features).
Landforms of glacial erosion comprise large-scale features (e.g. glacial troughs, corries,
breached watersheds, truncated spurs and large roches moutonnees and ice-moulded hills)
and medium- to small-scale features (e.g. ice moulded bedrock, small roche moutonnees, pforms and striations). As a broad generalisation, the intensity of glacial erosion was greatest
in the west and north of Scotland and least in the south and east, and this is reflected in the
distributions of the different landforms (Figure 4). At a broad scale, these forms occur in
different combinations to produce several broad categories of landscape type.
Areal scouring is most distinctively recognised as the cnoc and lochan topography
characteristic of Sutherland and South Harris, for example, but it also constitutes the main
landform element of other areas such as much of Shetland, parts of west and south
Lochaber, and parts of Galloway (Figure 4).
Selective linear erosion occurs where glacial modification of the landscape has been more
localised in the form of overdeepening of glens by powerful ice streams, but adjacent
interfluves and plateau surfaces have remained little modified. The classic example of this
type of landscape is the Cairngorms, but it is widely developed across the central and
eastern Grampians (e.g. from Ben Alder to Glen Clova) (Figure 4).
Landscapes of mountain glaciation are recognisable through their heavily dissected alpine form,
including corries, aretes and valley glacier heads. In Scotland such landscapes are epitomised
by the Cuillin of Skye and Rum and by the north Arran hills, but also occur in the northwest Highlands (Figure 4).
Page 38
10 January, 2002
Figure 4
Distribution of different landscapes of glacial erosion in Scotland (From Gordon, in
press, modified from Haynes, 1983).
Page 39
10 January, 2002
Ice-moulded lowlands consist of streamlined hills and features such as crag and tail forms and
rock drumlins. Notable examples occur in the Midland Valley and on the southern side of
the Forth in the Lothians (Edinburgh Castle rock is one component of this suite of features)
and in Caithness (Figure 4).
Areas of minimal erosion are distinguished by the presence of relict features such as deeply
weathered bedrock and tors. The most extensive area of this type of landscape is in NE
Scotland.
Inevitably there is some spatial overlap in these landscape categories, for example between
features of mountain glaciation and landscapes of selective linear erosion (as in the
Cairngorms) and between areal scouring and mountain glaciation (as in the mountains of
Knoydart).
Meltwater channels eroded by glacial meltwaters occur widely in Scotland. They are
particularly well developed along the northern margin of the Southern Uplands and the
southern margin of the Pentland Hills, on the northern flanks of the Cairngorms and near
Dinnet.
4.2.2 Landforms of glacial and glaciofluvial deposition
The landforms and deposits of glacial deposition are of national importance for:
•
•
•
•
•
the information which they provide on landscape form and evolution;
the information they provide on glacier properties and processes;
the information which they provide for testing models of glacier dynamics;
the diversity which they add to the geomorphology of Scotland;
the diversity they add to the landscape and habitats in terms of topographic and
hydrological units (e.g. kame and kettle topography) and in terms of soil parent
materials.
Subglacial deposits are widespread in the Midland valley and the lowlands of eastern and
southern Scotland (Figure 5). They also occur on the floors of Highland glens and Southern
Uplands valleys, although often buried by other deposits. The most common type of deposit
are till sheets with limited surface expression. In many parts of the lowlands, these till sheets
have been drumlinised to form characteristic low, streamlined hills (as in west-central
Scotland including the Glasgow area, the Tweed valley and the Solway lowlands). Other
streamlined depositional features include crag and tail forms (e.g. in the Tweed valley),
although these can often be rock cored.
Ice-marginal forms comprise lateral and end moraines. These occur most commonly in
Highland glens and corries and on Skye and Mull, where they are associated with the Loch
Lomond Readvance. Moraines associated with the last ice sheet are less common, and often
controversial; important examples include the Wester Ross Readvance end moraine, the
recessional moraines in the inner Moray Firth, the central Islay moraine and the readvance
moraines on the northern
Page 40
10 January, 2002
Figure 5
Page 41
Distribution of drift deposits in Scotland (from Gordon, in press, after Haynes, 1983;
Sutherland and Gordon, 1993; Ballantyne and Dawson, 1997).
10 January, 2002
flanks of the Cairngorms. A very distinctive type of moraine is the ‘hummocky’ moraine that
occurs in many Highland glens. In many cases the forms have a clear alignment and are
believed to have formed at the margins of receding Loch Lomond Readvance glaciers; others
may be of subglacial origin. Particularly good examples of hummocky moraine occur in
Torridon, on Skye and on Mull.
Glaciofluvial landforms and deposits are formed where large amounts of meltwater were
produced during deglaciation (Figure 5). They comprise sand and gravel deposits formed at
or near former ice margins or in association with stagnant ice. Such deposits assume a
variety of forms, including eskers, kame terraces and kame and kettle topography. Classic
examples of large eskers occur at Carstairs, near Inverness and at Bedshiel, but there are
many others, as on the northern and western flanks of the Cairngorms, near Dinnet, in
Abernethy Forest and north of Aberdeen. Kame terraces are well developed at Torvaine
near Inverness, in Strath Nairn and along Loch Etive. Kame and kettle topography is
widespread in lowland Scotland, for example in the upper Clyde valley, in north Fife, the
Angus glens and the Moray lowlands. Proglacial forms include outwash plains deposited in
front of the glaciers. In many cases these have been dissected to form flights of terraces
commonly found in many glens and valleys. Particularly good examples occur in Strathmore
near the mouths of the Angus glens, in Glen Feshie, in Gleann Einich and in Glen Roy.
Glaciolacustrine landforms and deposits principally include deltas formed where glacial rivers
built up large accumulations of sediment in former ice-dammed lakes. Particularly good
examples occur at Achnasheen, in north Fife, on Skye, in the northern Cairngorms and in
Glen Spean. Other features associated with glacial lakes include shorelines and sub-aqueous
moraines. Glacial lake shorelines are most spectacularly developed in Lochaber, particularly
in Glen Roy (the Parallel Roads), but other examples occur at Loch Tulla, Glen Doe and
Achnasheen. Sub-aqueous moraines (cross-valley moraines) are best displayed in Glen Doe
and Glen Spean.
4.2.3 Periglacial landforms
Periglacial landforms and deposits are of national or international importance for:
•
•
•
•
•
•
•
the information which they provide on landscape and landform evolution;
the information which they provide on past climates;
the diversity which they add to the geomorphology of Scotland;
the diversity they add to the landscape and habitats, particularly in the uplands, in terms
of small-scale topographic units (e.g. nivation hollows, solifluction terraces);
the present-day maritime periglacial processes, characterised by wet and windy
conditions rather than extreme cold as in arctic or alpine mountain regions;
the interactions between present day processes and vegetation patterns in the uplands;
their contribution to soil formation.
Periglacial processes operated on the landscape beyond the glacier margins during the many
periods of cold climate during the Quaternary and continue to be active on the higher
mountains today (Ballantyne and Harris, 1994). Most periglacial features date from the latter
part of the last ice age. Evidence for periglacial features associated with permafrost in the
lowlands is in the form of ice-wedge casts and ice-wedge polygons (Figure 6). The former
have been recognised mostly in gravel pits; the latter have been identified on air
photographs, almost exclusively in Buchan. Other evidence includes disturbed soil horizons
Page 42
10 January, 2002
(cryoturbations) and indurated horizons in many soils. Evidence for periglacial disturbance
and movement of the soil (solifluction) is widespread on lowland slopes. The depth affected
is usually 1–2 m, but in valley floors, particularly in the Southern Uplands, greater thickness
of solifluction deposits have accumulated. In Buchan, there is evidence for buried periglacial
deposits of some antiquity, pre-dating the last ice age.
In the uplands, the most widespread evidence for former periglacial activity is the cover of
frost-weathered debris on summits and upper slopes. This cover takes the form of
blockfields and blockslopes. On many slopes the debris has been modified by solifluction to
form a variety of lobes and sheets. On a number of summits in the NW Highlands the in situ
debris has a clear lower limit, defining a periglacial trimline which represents the upper limit
of the last ice sheet. Large-scale, relict patterned ground features (circles and stripes) locally
occur on Scottish mountains. Below steeper rock slopes there are extensive accumulations
of rockfall talus, which in some places were modified by permafrost during the Loch
Lomond Stadial to form protalus ramparts and protalus lobes or rock glaciers, notably in the
Cairngorms. Large rockfalls contributed to the large size of some of these features, as at
Beinn Shiantaidh (Jura), Baosbheinn (Wester Ross) and Strath Nethy (Cairngorms). Wind
activity has also been important in the production of postglacial sand accumulations on
Scottish mountains, particularly on Torridonian sandstone, on the Trotternish ridge on Skye
and on Ward Hill (Orkney) and Ronas Hill (Shetland). The present-day maritime periglacial
conditions give rise to three main types of processes associated with (1) frost action and
late-lying snow; (2) wind action and (3) modifications of talus and other slopes.
4.2.4 Quaternary stratigraphy
Quaternary stratigraphic sites are of national and international importance for:
•
•
•
the information which they provide on long-term landscape and landform evolution;
the information which they provide on past climates and environmental changes;
the diversity which they add to the landscape history of Scotland.
The surface sediments in the present landscape provide an archive of geomorphological
processes during the ice age period. Most of these sediments date from the last ice age, but
in areas where glacial erosion was limited older deposits lie preserved beneath. Where
these deposits contain organic materials, they are invaluable sources of palaeoenvironmental
information. Similarly, peatbogs and loch floor sediments provide an archive of postglacial
processes and environmental changes. As reflected in the fossil record, the flora and fauna
of the cold periods show restricted diversity of species and, not surprisingly, the
predominance of cold-tolerant types. Interglacials, on the other hand, are characterised by
the absence of glacial, periglacial and glaciofluvial features in the geomorphological and
sedimentary record. They are often recognisable by periods of chemical weathering, soil
formation or the accumulation of organic material. Changes in the amount and types of
pollen preserved in organic deposits have been used to define systems of pollen zones, each
zone being characterised by particular vegetation types, from which climatic and
environmental conditions are inferred. Progressive changes in vegetation through time can
be reconstructed through sequences of pollen zones. Environmental conditions have varied
during different interglacials, and the presence of particular types of pollen can be diagnostic
of particular interglacials. Both terrestrial and marine molluscs and coleoptera (beetles) are
also useful in reconstructing past environmental conditions by analogy with their present
environments.
Page 43
10 January, 2002
Figure 6
Distribution of Late Devensian ice-wedge polygons, ice-wedge casts and cryoturbations
in Scotland (after Ballantyne, 1997)
Page 44
10 January, 2002
Sites containing long sequences of deposits pre-dating the last glaciation are today relatively
scarce (Figure 7). Many of those known were located last century during temporary
excavations for public building works and railways, or during mineral extraction, and are no
longer accessible; others have been discovered in more recent sand and gravel quarries.
Only a few such sites remain accessible today, notably in Shetland, in the Outer Hebrides,
around Inverness and in NE Scotland. Such sites are generally unique and of the very highest
scientific importance. Many more sites are available for demonstrating the sequence of
events during the last glaciation and the period of transition to the present interglacial, as
well as during the latter. Of particular interest are networks of sites that show:
•
•
•
•
•
the glacial/interglacial history of Scotland;
the main regional variations in the sequence and pattern of ice movements (e.g. the
onshore movement of ice across Caithness and Orkney represented by shelly tills and
erratics derived from the sea floor, and the interaction of ice masses from sources in the
Highland and Southern Uplands in Ayrshire);
the sequence of geomorphological events during the Late-glacial (including sites in the
type area for the Loch Lomond Readvance and sites demonstrating sea level changes);
the sequence of environmental changes during the Late-glacial;
the major regional patterns of vegetation succession during the Late-glacial and
Holocene (including forest history).
Page 45
10 January, 2002
Figure 7
Sites with terrestrial organic deposits, faunal remains and raised beach deposits that
pre-date the Late Devensian (From Gordon, in press, after Sutherland, 1984;
Sutherland and Gordon, 1993; Whittington et al., 1993). Base map © Crown
Copyright. Based upon Ordnance Survey data with the permission of the Controller of
Her Majesty’s Stationery Office. Licence no. GD03135G0005
Page 46
10 January, 2002
4.2.5 Landforms and deposits indicative of relative sea level change
These landforms and deposits are of national or international importance for:
•
•
•
•
•
•
the information that they provide on long-term coastal evolution and
palaeoenvironmental change in the coastal environment;
the information that they provide for testing models of the rheology of the Earth’s crust;
their relationships with glaciation;
the diversity that they add to the coastline of Scotland;
the diversity of features found within the limited geographical area of Scotland, which is
probably unique in global terms;
the information that they provide on possible future response of the coastal zone to
predicted global sea level rise.
In parallel with the growth and decay of ice sheets, significant changes have occurred in the
coastal zone of Scotland associated with a complex interplay of changing land and sea levels.
World sea level has varied according to the volume of water locked up within the world’s
ice sheets, being lower during glacials than interglacials. The level of the land has also varied,
sinking under the weight of advancing ice sheets and rising up again when they melted. Such
changes are evident in beaches, shore platforms and marine sediments now raised above the
present sea level. Submerged shoreline features and drowned valleys also point to relatively
lower sea levels in the past.
Landforms and deposits associated with relative sea level changes occur widely around the
coast of Scotland. They comprise the following features.
Shore platforms of various ages are represented on both the east and west coasts of
Scotland. The Inner Hebrides, and Islay and Jura in particular, are the type areas for the High
and Low Rock Platforms, which pre-date the last glaciation. The Main Rock Platform
extends from the Firth of Lorne to Ayrshire and is particularly well developed in its type
area around Oban and eastern Mull; it is also represented in eastern Scotland in buried
gravel layers in the Forth and inner Moray Firth areas. An intertidal rock platform is present
along much of the east coast of Scotland and is well developed, for example at Dunbar and
in Kincardineshire.
Raised beach terraces occur extensively as ‘staircases’ around the coast of mainland Scotland,
in the area where isostatic uplift has outpaced eustatic sea level rise at different times.
Broadly, raised beach deposits may be categorised as Late-glacial and postglacial. The former
reflect the rapid isostatic uplift as the last ice sheet melted and generally occur at higher
levels, up to c. 40 m asl (above sea level), than the postglacial beaches. Among the most
spectacular of the lateglacial beaches are the shingle ridges on Jura and on the southern
shores of the Moray Firth (e.g. at Spey Bay). Postglacial shorelines generally occur at lower
levels (up to 12 m OD), the highest sometimes at the base of a prominent cliff line which
may be partly exhumed. This cliff line and postglacial beaches are extensively developed
along the east and west coasts of Scotland, where topography and sediment supply were
suitable. Large progradational forelands developed where sediment supply was particularly
abundant (e.g. Morrich More, Tentsmuir, Spey Bay–Culbin, Runahaorine Point). Some
former beaches are in fact buried beneath later beaches (e.g. most notably the Forth valley,
but also in the Tay estuary, Ythan estuary and the inner Moray Firth areas) during the
period of low relative sea level during the latter part of the lateglacial and the early
Holocene.
Page 47
10 January, 2002
Raised estuarine deposits include glaciomarine deposits formed during the period of wastage
of the last ice sheet and postglacial estuarine deposits. The most extensive of the former
include the Errol and Clyde beds. The Errol beds, with their high arctic faunas, are mostly
restricted to eastern Scotland, to the estuaries of the Forth, Tay and Moray Firths. The
Clyde beds, with their arctic to boreal faunas, are predominantly developed on the west
coast around the Clyde estuary. Postglacial raised estuarine deposits were formed during
and following the Main Postglacial Transgression. They occur extensively in eastern Scotland
in the Forth, Tay, and Moray Firth areas, and to a lesser extent in most low-lying river
valleys (e.g. Ythan, Montrose basin). In some locations, interbedded sequences of terrestrial
and estuarine deposits record short-term fluctuations in sea level, including a major tsunami
on the east coast c. 7000 BP associated with submarine slides on the Norwegian continental
shelf.
Inter-tidal and sub-tidal terrestrial sediments occur at various locations towards and beyond the
periphery of isostatic uplift, where sea level rise has outpaced uplift during much of the
Holocene. Such sequences of sediment (e.g. peat, saltmarsh deposits) record the drowning
of the coastline. Particularly good examples occur in Shetland, the Outer Hebrides and on
Coll.
Isolation basins are natural depressions which at various times have been connected to the
sea or isolated from it, depending on the rate of crustal uplift and the rate and direction of
sea level change. Changes in relative sea level are recorded in the sediments and biological
assemblages (saline–brackish–freshwater transitions) preserved in the basins. Such sites
provide valuable evidence for establishing the pattern and timing of sea level and coastal
environmental changes. Sites investigated so far have been in the
Arisaig–Morar–Ardnamurchan area, Rum and North Uist.
High-level shelly deposits are deposits of shelly marine clays occurring at altitudes up to 150 m
OD at various locations in Scotland (e.g. in the Inverness, Kincardineshire, Kintyre and
Ayrshire areas). The origins and significance of these deposits are controversial. Either they
are in situ and indicate a period or periods of significantly higher sea level, or they are rafts
of marine sediment transported by glacier ice. They are of major research importance.
Coastal waterfalls occur where the normal processes of river erosion have been interrupted
by changes in sea level or isostatic uplift of the land, leaving the river channel suspended.
Although coastal waterfalls are not of major research importance, they are significant
landscape features (particularly along the west coast) that are of interest to tourists; also of
note are the waterfalls along the east coast from Aberdeenshire to Angus and the small
waterfalls in the coastal deans of Berwickshire, which are locally significant given the lack of
waterfalls within the relatively low-lying Tweed catchment.
4.2.6 Palaeoenvironmental records in lochs and bogs
Such sites and their palaeoenvironmental records are of national importance for:
•
•
provision of continuous, high resolution records allowing detailed reconstructions of
patterns of climate, vegetation succession and soil stability/instability from the time of
deglaciation to the present day based on multi-proxy indicators;
provision of critical evidence for establishing the timing and patterns of deglaciation at
the end of the last ice age;
Page 48
10 January, 2002
•
•
•
•
•
•
•
key sites for particular phenomena of palaeoecological importance (e.g. relating to plant
refugia and the survival of arctic–alpine species on Scottish mountains);
provision of representative sites to show the major regional variations in vegetation
history and environmental change as represented in various proxy records; such sites
will normally have good modern pollen analyses, long records and be supported by
radiocarbon dating;
the spread of tree species across the landscape during the middle Holocene and the
pattern of natural woodland before human clearance;
the impact of human activities on the landscape through deforestation and early
agriculture;
they provide analogues of how plant communities might respond to future
environmental changes;
they allow contemporary ecological patterns and processes to be placed in a longerterm context;
they provide records of human impacts, e.g. environmental pollution.
The sediment accumulations in lochs and bogs provide invaluable archives of
palaeoenvironmental change. As peat or loch sediments accumulate, they build up an in situ
record of palaeoenvironmental indicators: plant remains, pollen, beetles, diatoms,
chironomids, charcoal, volcanic ash and particulate pollutants. Analysis of these remains,
combined with various forms of dating, can provide unique insights into palaeoecological and
palaeoenvironmental changes over timescales ranging from hundreds to thousands of years,
as well as human impacts on the landscape. Such records allow contemporary ecological
patterns and changes to be placed in their historical context (e.g. the decline of heather
moorland in the uplands) and they show how plant communities might respond to future
environmental changes. Palaeoecological studies may also contribute to nature conservation
in a number of significant ways: assessment of the naturalness and fragility of ecosystems,
the conservation status of rare species and ecosystem response to human activities and
effects such as acidification. Palaeoenvironmental records are often a valuable (sometimes
the only) source of baseline information for monitoring environmental change or
undertaking ecosystem restoration.
Lateglacial sites are of crucial importance since they record environmental changes during an
episode of rapid shifts in climate, vegetation and geomorphological processes. The close
correspondence between the terrestrial records from Scotland and Greenland ice-core
records also allows changes in Scotland to be placed in a wider North Atlantic and
European context.
Some sites are important for the information they provide on the timing and rate of
deglaciation (e.g. sites in the Teith Valley, Rannoch Moor, Strath Spey). Others are
important for the evidence they provide on a regional level for patterns of climate change
and vegetation history (e.g. Beanrig Moss, Whitlaw Mosses, Din Moss, Stormont Loch, Loch
Kinord, Cam Loch, Pulpit Hill, Loch an t’Suidhe, Morrone). A few sites contain beetle
remains that have allowed additional palaeoenvironmental inferences to be made (e.g.
Bigholm Burn, Redkirk Point). Recent discoveries of tephra remains from Icelandic volcanic
eruptions have allowed additional forms of dating and correlation between sites as well as
increased resolution of environmental changes (e.g. Borrobol, Whitrig Bogs, Tynaspirit).
Holocene sites are important for the information they provide on postglacial patterns of
climate change and vegetation history. These demonstrate the pattern of vegetation
Page 49
10 January, 2002
development following the end of the last ice age, including the spread of trees and the
regional woodland history (e.g. Abernethy Forest, Loch Dungeon, Black Loch, Rannoch
Moor, Gribun and Lochs Ashik, Cleat and Meodal on Skye, Loch of Winless, Loch Maree,
Gleann Mor Hirta, Lochan an Druim). Human impacts through woodland clearance during
the last 5000 years are clearly evident in many pollen records (e.g. Black Loch, sites in Strath
Spey). More recent impacts have been revealed by palaeolimnological studies that have
shown that many lochs, including those in remote areas, are contaminated by fly-ash
particles and trace metals, and have undergone significant acidification from atmospheric
pollution over the last 100 years (e.g. Round Loch of Glenhead, corrie lochs in the
Cairngorms, Lochnagar).
4.3 Coastal geomorphology
The coastal landforms and deposits of Scotland are of national or international importance
for:
•
•
•
•
•
•
•
•
•
•
•
•
•
the exceptional diversity of landforms and processes (owing to the wide variations that
exist in all the main factors controlling coastal development);
the study of coastal evolution and particularly the interplay of relative sea level change
and changes in sediment supply;
the machair of the Highlands and Islands, which is virtually unique in western Europe
features associated with high-energy, exposed environments (rock coasts, beach
complexes);
the exceptional dynamics of many beach complexes, especially in the Highlands and
Islands;
the diversity of dune and machair landforms, including some of the largest and most
impressive blown sand features in Great Britain;
some of the most extensive areas of sand coast progradation in Great Britain;
the highest and most impressive cliff coast features in Great Britain;
features associated with isostatic uplift (carse, raised beaches);
features associated with glaciated coasts (relict shore platforms, beach complexes and
shingle structures);
rock coast features associated with resistant igneous and metamorphic rocks;
relatively young saltmarsh features that allow comparisons with more developed
systems in England;
saltmarshes associated with loch head environments.
The coastline of Scotland shows an exceptional diversity of landforms relative to the size of
the country, as well as an inherent dynamism both spatially and temporally. This diversity
and dynamism reflect the underlying variations in environmental setting and process
controls associated with rock type and structure, climate, tidal-energy and wave-energy
environments, the effects of glaciation and sea level change, and the availability of sediment
supply. Such is the range of these parameters that most types of coastal setting are
represented somewhere on the Scottish coast.
Much of the coastline of Scotland comprises a range of, in geological terms, relatively old
rock types of variable resistance. The variations in hardness and in rock structure (jointing
and bedding) exert a fundamental control both on overall coastline form and on the detailed
morphology of the landforms.
Page 50
10 January, 2002
Climate is also a major determinant of coastal processes through its control primarily on
wave-energy environments and also on terrestrial processes such as sandblow. Thus,
variations in wetness and windiness, and correspondingly in vegetation patterns, are
reflected in variations in beach and sand stability. Extreme variations occur in the wave
energy environment ranging not only from the high energy coasts of the Northern Isles and
Outer Hebrides, exposed to the full Atlantic swell, to the comparatively sheltered estuaries
of the east coast, but also between the outer and inner coasts of these island groups.
The effects of glaciation are apparent in the shaping of estuaries, sea lochs and low rock
coasts and in the changes of relative sea level that accompanied the growth and decay of the
Scottish ice sheets. Glaciation has also had a fundamental influence on the pattern of
sediment supply to the coastal zone, with vast volumes of glacially eroded debris deposited
on the continental shelf at the end of the Ice Age. These were later reworked and moved
towards the shore as sea level recovered to form the basis of our present beach, sand dune
and machair systems. Patterns of glacial erosion and deposition have thus strongly shaped
the present form of the coast both directly and indirectly.
Sediment availability is also a key factor influencing the present stability of many parts of the
coastline. Where sediment supply is abundant, as at Tentsmuir by the mouth of the Tay, the
coastline is, locally, advancing or prograding seawards; where sediment supply is in decline,
the coastline is more usually retreating through erosion. According to the local process
dynamics, progradation and erosion may be operating on adjacent stretches of coast.
Through temporal and spatial variations in these controls, Scotland’s coastline is constantly
changing. On a human timescale, however, it may be regarded as being in a state of dynamic
equilibrium.
The interest of the coastal geomorphology of Scotland is founded on the exceptionally
broad range of landforms, sediments and processes which exist there and the interactions
between them. These have considerable value, not just in terms of understanding the
evolution of the coastline through time but particularly in understanding the contemporary
changes taking place, the factors that underlie them and how they may affect society.
Broadly, the interest of the coastline may be classified into sand beach complexes, shingle
structures, rock coast features and saltmarshes.
4.3.1 Sand beach complexes
Sand beach complexes are widely distributed throughout Scotland (Figure 8a). Typically,
they comprise beaches, sand dunes, machair, links or some combination of these. In the
Highlands and Islands they are typically associated with high-energy, exposed environments,
whereas in the lowlands lower levels of energy and exposure are prevalent. This, and
variations in sediment availability, results in certain differences in character between the
beaches in these regions.
Beaches of the Highlands and Islands (Zones 1–6, 8, 14). Sandy beaches make up less than 5%
of the total length of coastline of the Highlands and Islands. Most of the beaches in the
region occur on the islands on the open, high-exposure Atlantic coasts and to a lesser
extent in north and west Sutherland. This distribution is related to three principal
controlling factors: generally high exposure, coastal relief conducive to sediment
Page 51
10 January, 2002
accumulation (namely a relatively shallow offshore gradient and, locally, low relief onshore
where sand may collect) and generally high sediment availability for beach construction.
Many beaches in the region are associated landward with blown sand deposits in the form of
sand dunes or machair (dune pastures with lime-rich soils), forming what are termed beach
complexes. A key attribute of many such complexes is their dynamic character. This is most
clearly manifest by drifts of bare sand, the extreme distance and height to which sand may
be blown inland (> 100 m OD in Barra) and by the highly dissected nature of many dune and
machair surfaces. A number of these systems also contain outcrops of aeolianite, an unusual
form of cemented dune sand, rarely found outside the machair areas of Scotland.
The beach complexes of the region are thus among the most distinctive soft-coast systems
of Britain, particularly where they are associated with machair development, and represent a
resource of international significance.
Beaches of the lowlands (Zones 9, 16–19, 21). Sandy beaches make up approximately 12% of
the total length of coastline of the lowlands, significantly higher than in the Highlands and
Islands. Many beach complexes are, moreover, vast by comparison, as in Aberdeenshire
where dunes reach 45 m in height. The primary reason for this is the relative abundance of
glacially derived sediment that was laid down on the nearshore shelf during and after the last
ice age and which was, during the Holocene transgression, driven onshore and,
subsequently, stranded as sea levels fell again across the region.
This abundant sediment resource and the relatively less severe wind and wave climate
experienced by the lowlands also results in typically more stable dune and links surfaces
than are evident further north and, often, multiple dune ridges.
A key landform element of the lowland beaches is the existence of vast prograding coastal
forelands at the mouths of some of the firths, as at Barry Buddon and Morrich More.
Page 52
10 January, 2002
Figure 8a
Distribution of coastal sand dunes in Scotland.
These broad peninsulas are typically underlain by sand and shingle and blanketed by a variety
of dune forms including, at some sites, rare parabolic dunes.
4.3.2 Shingle structures (Zones 1, 2, 9 and 14)
Modern, active shingle structures occur sporadically around the Scottish coast but are most
common in the Northern Isles, Western Isles and the Moray Firth. Active shingle spits are
also best developed on the Moray Firth coastline, especially at Spey Bay, Culbin and
Whiteness Head. Historical records indicate that these typically migrate a few tens of
metres per year but can, under certain conditions, extend by over 100 m in the same
period.
The widest range of active and semi-active shingle structures, such as storm beaches, bars,
spits and tombolos, is evident on those coastlines that have undergone progressive
submergence through the Holocene, namely in the Western and Northern Isles, and, in
particular, on Shetland.
Extensive suites of raised, now inactive, shingle ridges exist in many areas but are best
preserved in Jura, Islay and parts of the Moray Firth (see Section 2.5.2).
4.3.3 Rock coast features
Rock coast features are characteristic of extensive parts of western Scotland from the
Clyde estuary to Shetland and including the north coast of the mainland (Figure 8b). They
include large glaciated sea lochs, low ice-scoured coasts, low cliffs with shore platforms of
Page 53
10 January, 2002
variable width and extent and high cliffs, varying according to patterns of rock type, glacial
erosion and isostatic uplift. On the east and southwest coasts, rock coasts are more
intermittent or buried in drift or sand overlying shore platforms.
High cliffs and their associated landforms are most clearly manifest around many of
Scotland’s islands, particularly in the north and west, and, locally, along the east coast of the
mainland. This diversity of forms is best illustrated around the island of Papa Stoer in
Shetland and parts of Hoy and Mainland in Orkney, where the full range of features,
including cliffs, stacks, arches, geos, blowholes and wave cut notches, is expressed.
4.3.4 Saltmarshes
Saltmarshes are relatively limited in distribution in Scotland and are confined to a number of
estuary, loch head and barrier beach settings. The most extensive marshes occur along the
inner shores of the Forth, Tay and Solway Firths. In the Highlands and Islands the sheltered
character of many of the sea lochs permits the development of marshes at the loch head
and along some shores. These often form directly on top of shingle but, as a result of the
limited sediment supply, are rarely extensive. Some of the best-developed saltmarsh systems
are located in the lee of shingle spits or barrier beaches, especially fine examples occurring
at Morrich More and Culbin.
Figure 8b
Page 54
Distribution of coastal cliffs in Scotland.
10 January, 2002
4.4 Fluvial geomorphology
The river landforms and processes of Scotland are of national or international importance
for:
•
•
•
•
•
•
•
•
•
•
gravel bed rivers;
classic sedimentary features;
mountain torrents;
east–west hydrological contrasts;
evidence of the geomorphic impact of extreme floods;
reworking of Late Quaternary deposits;
re-occupation of meltwater channels;
they provide information on the rate of landscape evolution and environmental change
during the Pleistocene;
sensitivity to change is important for landscape management, planning and hazard
prediction;
relatively undisturbed planforms.
The deeply dissected relief of the Scottish Highlands, the marked rainfall gradient from west
to east across the country and the abrupt juxtapositioning of upland and lowland reaches in
the piedmont zone has meant that Scottish rivers offer a richer variety of form and process
than others in the UK. Thus, many of Scotland’s undisturbed rivers are at least of national
importance. In this section, the controls on channel form and process are discussed, and the
regional characteristics of Scottish rivers are outlined.
4.4.1 Controls on channel form
The form of, and processes operating in, Scottish rivers depends, in part, upon rainfall and
run-off characteristics, slope, underlying geology, and also upon the glacial legacy of eroded
basins and high floodplain sediment availability. Scotland has a marked west–east
precipitation gradient due to the westerly origin of most of the cyclones reaching Britain
and to orographically triggered rainfall in the north and west. Sites on the west can
experience rainfalls in excess of 3000 mm per year, whereas those on the east may only
experience rainfall of around 700 mm. This spatial variation in total rainfall combines with
variations in temperature, altitude and vegetation cover to produce a spatial variation in
evapotranspiration, although when compared internationally Scotland has generally low
levels of evapotranspiration. Thus, parts of the NW Highlands record rainfall–run-off ratios
of over 75%, with the majority of Scotland recording ratios of over 50%, and severe drought
is relatively rare in Scotland. In contrast, much of south-east England has rainfall–run-off
ratios of only around 40%, which combine with the increased population pressure to place
more stress on their river systems in dry periods.
The west–east variation in run-off would suggest that the largest and most powerful rivers
of Scotland be located in the west. This, however, is not the case. The main watershed in
Scotland is asymmetrically located and short rivers drop off the divide flowing west, while
longer, larger rivers flow east. It is only in the Southern Uplands that the divide between the
Clyde and the Tweed is more symmetrically located. The asymmetry is the direct result of
glaciation during the Quaternary, when the main ice shed was asymmetrically located. Short,
steep, active ice streams flowed west into the sea from an ice shed approximating the
current watershed, producing a series of deeply incised glaciated valleys. Ice streams flowing
Page 55
10 January, 2002
east were longer and had a more gentle gradient. They left behind the larger valleys. After
deglaciation, rivers merely occupied the courses excavated by the ice streams, with some of
the upper reaches of upland channels being cut directly into bedrock and representing the
courses of former subglacial meltwater channels. These bedrock reaches alternate with
alluvial basins, forming a stepped, long profile and an overall pattern resembling beads on a
string.
Repeated glacial erosion has left a significant volume of glacial and glaciofluvial deposits on
the valley floors. These comprise sand, gravel and variously sized boulders, can be entrained
through lateral channel migration. As a result of this ready supply of sediment, the larger
rivers of Scotland (e.g. the Tweed, Tay and Spey) have gravel beds down to their marine
limits. Without the constant reworking of the glacial deposits, the bed material would
become progressively finer downstream and would comprise sand and clay in the lower
reaches. Glacial erosion has also left lochs within the river courses, some of which were
formed through glacial scouring (e.g. the lochs within the Tay catchment), others of which
are former kettle holes (e.g. Loch Leven in the Eastern Lowlands) or are moraine dammed
(e.g. Lake of Menteith in West Central Belt) and have become incorporated into the
drainage system after deglaciation. Lochs dampen flood waves and thus reduce stream
power downstream, and lochs also act as sediment traps.
The form and location of many of Scotland’s waterfalls can be attributed to glacial erosion.
Waterfalls are located where hanging valleys drop abruptly into glacial troughs, are found
within the stepped long profile of glacial troughs, at the coast, in corries or in meltwater
gorges created by rivers flowing away from the decaying ice sheets. Waterfalls are also
found around geological fault lines. Because waterfalls evolve by upstream migration (the
overhanging cap rock is undermined when the underlying weaker rock is eroded), the
current location of the waterfall may be some distance from the fault. Waterfalls are not a
significant area of research in Scotland and the fast-flowing water and steep ravine sides can
make them relatively difficult habitats. Nevertheless, mosses and liverworts thrive on damp
rocks, and the waterfalls themselves are important components of the landscape,
contributing to tourism and enjoyment of the environment.
The current form of Scottish rivers is the result of processes operating over a number of
different timescales: the geological controls of structure and lithology have been dominant
for millions of years; the glaciated valleys and other features relating to glaciation formed
tens of thousands of years ago; terraces, floodplains and fans formed within the Holocene;
channel migration, bar formation and bank erosion operate at a timescale of hours to
decades and centuries. Human influences also operate at a range of different timescales
from immediate (e.g. river engineering) to thousands of years (deforestation of the natural
forest cover altering sediment supply).
4.4.2 Spatial patterns
Channel form and pattern change from the uplands to the lowlands. The downstream
decline in slope generates changes in the sediment transport regime, channel pattern and a
reduction in the size of sediment that is transported. Scottish rivers rarely display classic
‘downstream fining’ (where the bed material particle size becomes smaller with increasing
distance downstream) along their entire length. In addition, the division of river systems by
reference to channel planform is complicated by the existence of transitional forms. Instead,
material fines locally in reaches between local baselevel controls, e.g. between tributary
Page 56
10 January, 2002
inputs, which may also play a significant part in determining planform. In general, the
catchment of a river can be divided into three zones with the characteristic form identifiable
in each zone
4.4.3 Headwater reaches
A river whose source is in the Highlands will begin as a boulder bed mountain torrent [e.g.
the Allt Mor (River Druie) in the Cairngorms Massif and the Allt Mor (upper River Nairn) in
Central Highlands]. These channels are steep, contain large, boulder-sized bed material and
operate as a binary system where the sediment transport is ‘switched off’ for the majority of
the year (and the channels are stable then) but are ‘switched on’ during extreme flood
conditions. The impact of large, rare floods may persist longer in upland environments [e.g.
the Allt Mor (river Druie) in the Cairngorms Massif] where the normal channel regime is
unable to begin the process of channel reworking following a large flood event, because the
boulders moved during flood are far in excess of those normally moved. The presence of
bedrock reaches and gorges in the upper reaches is related to erosion by glacial meltwater
during and after the Pleistocene. Moving gradually downstream, but still within the mountain
zone, many rivers pass through alluvial basins: glaciated valley floors (separated from each
other by reaches of bedrock) that have been infilled by alluvium. The local gradient within
the alluvial basins is extremely low so channels often develop meandering planforms more
commonly found in lowland reaches. The junction between the steep mountainside and the
flat alluvial basin can form a hydraulic discontinuity and can be the interface between
different types of geomorphic activity. Outwith the alluvial basins, generally high gradients
and the abundance of sediment available for entrainment produces braided (or highly
divided) channels which are extremely active (e.g. Upper River Feshie in the Cairngorms
Massif or Dorback Burn in the North East Glens). The mechanism for sediment transport in
the head waters is predominantly bed load transport (whereby the large boulders roll and
bounce along the river bed during flood). At any point in the uplands, bedrock may outcrop
into the river, separating reaches and forming a step within the long profile.
4.4.4 Middle reaches
Downstream of the bedrock channels, mountain torrents, alluvial basins and truly braided
rivers (but often still within the uplands), the gradual reduction in bed material size and
channel slope is often accompanied by a reduction in confinement and a widening of the
valley floor. This often produces wandering gravel bed rivers that can be divided or
undivided (and consequently they differ from braided rivers) and of low to medium sinuosity
(e.g. River Tulla in Lochaber and the middle River Feshie in the Cairngorms massif).
Sediment supplied from bed, banks, undercut terraces and tributaries helps control the
degree of channel stability. If the sediment size of the input is particularly large, the river
may be locally stabilised since it is unable to transport the material on its bed. Rivers in their
middle reaches are rarely confined by bedrock and are usually alluvial (incised within
sediments that were deposited by the river at an earlier stage, so the banks are composed
of similar material to the bed material, which makes them particularly vulnerable to
erosion). In these middle reaches, lochs act as sediment traps and help regulate flow.
Downstream of such lochs, the channel gradient and sediment input from the banks and
from tributaries ensures that the channels become rejuvenated and show many of the same
characteristics as those upstream.
Page 57
10 January, 2002
4.4.5 Lowland reaches
Lowland reaches are only found in a narrow coastal fringe around the Highlands and
Southern Scotland, although they are more extensive in the Central Belt. Thus, they
constitute only a small proportion of the rivers of Scotland. Unlike other parts of the
country (e.g. the mouth of the River Spey in the North East Coastal Plain or the mouth of
the River Tweed in the Eastern Lowlands), rivers in the central part of Scotland generally
have sand-sized bed material. Lowland river channels typically have a meandering or a
sinuous–straight planform (e.g. the River Endrick, or the meanders at the confluence of the
Clyde and Medwin Water). Usually extensively engineered to protect adjacent valuable
farmland from flooding, their naturally low gradient ensures that they are relatively stable
and are only able to gradually rework their floodplains. These low rates of reworking mean
that they often give rise to classic sequences of sedimentary features (e.g. the River
Endrick). Occasionally bedrock reaches can be found within the lowland rivers or providing
the demarcation between the upland and lowland zones (e.g. the River Clyde at Falls of
Clyde or the River Devon at Rumbling Bridge). Many lowland rivers terminate in the firths
and estuaries, which act as major long-term sediment stores. Estuarine reaches in the west
coast are fjordic in nature, but those in the south and east appear to be drowned valleys.
Headward migrating rapids in the east coast Ythan, Eden and Tay estuaries suggests that
they are continuing to rejuvenate through isostatic uplift, at a rate currently exceeding that
of sea level rise.
Within this idealised structure, ‘integrated’, ‘discordant’ and ‘progressive’ systems can be
found. Integrated systems are typically found in upland areas and comprise a sediment
source, transportational reach and sediment sink all within a small area. Discordant systems
occur when the hydraulic and sediment controls change abruptly, for example at the point
where the uplands emerge into the lowlands or where steep mountain streams emerge into
wide, flat glaciated valleys (e.g. Allt Mor, upper River Nairn). They are likely to be relatively
widespread in the Scottish Highlands but have not yet been researched in depth. In contrast
to these systems where change is abrupt, systems where the major controls change
progressively within a few kilometres can also be found (e.g. the Allt Dubhaig in Central
Highlands).
4.4.6 Within-channel features
The planform of the river channel (the view from above) is often used to differentiate
between channel type (i.e. separate rivers into meandering, braided or straight). When this
is combined with valley setting (e.g. upland or lowland), an overview of channel process
behaviour can be obtained. However, it should be remembered that the planform only
provides a one-dimensional view of the river channel form and processes. Features
developed within the channel also provide information about river behaviour and provide
information about vertical channel change. The main in-channel features found in alluvial or
gravel channels are:
•
Bars – Bars are deposits of sediment with length usually around that of the channel
width. Bars represent the vertical adjustment of the river bed to changes in flow pattern
and shear stress. There are five main types of bar: point bars, which form particularly on
the inner bank of meanders; alternate bars, which are found along one then the other
bank of the channel; channel junction bars, which develop where tributaries enter a main
channel; transverse bars (see riffles below), which may be diagonal to the flow; and midchannel bars, which are typical of braided reaches. Scroll bars are particular forms of
Page 58
10 January, 2002
•
•
point bars that record the gradual migration of the channel (through erosion at the
outside bend) as undulations in the surface of the point bar. Bars gradually migrate
downstream through erosion of the upstream face and deposition of sediment on the
downstream face. When the grains slide down the lee face they orientate themselves so
that the bedding planes are parallel.
Pools – Pools are natural areas of deep water formed within the river channel. The
development of alternating deeps and shallows is a particular characteristic of straight
and meandering channels. Pools are especially associated with the outside of meander
bends and are often formed in conjunction with side or point bars, giving the river an
asymmetric cross-section. Pools are usually found in conjunction with riffles in
pool–riffle sequences.
Riffles – Riffles are the shallow areas that often form in the middle of the channel at the
point where the flow crosses over from one bend to the other. Riffles usually form
between two pools and slope alternately towards one bank then the other (encouraging
meandering flow to occur, even in straight channels). One of the most marked features
of pool–riffle sequences is that the pools and riffles are regularly spaced, often occurring
at a distance of five to seven times the channel width.
Three main processes have been identified as operating in bedrock channels: corrosion,
which is the chemical action of water; corrasion, which is the mechanical (hydraulic and
abrasive) action of water when armed with particles; and cavitation, which is a process
associated with the effects of shock waves generated through the collapse of vapour
pockets in a flow with marked pressure changes. Cavitation can be an extremely effective
erosive agent but only occurs rarely because it requires extremely high velocities. Features
found within bedrock channels include plunge pools at the base of the fall which have been
scoured by mechanical action.
Features found within sand channels are similar to those found within gravel bed channels,
the main difference being the scale of features. Sand forms ripples, dunes, plane beds and
antidunes, the sequence given here being related to increasing stream power or increasing
velocity at a constant slope and depth. Ripples form at low shear stresses, whereas dunes,
the commonest form of bedform, develop at intermediate stresses. Antidunes form in
broad, shallow channels of relatively steep slope, and are low-amplitude bed waves that are
broadly in-phase with waves on the water surface. Like bars, ripples and dunes move
downstream through erosion of their upstream face and deposition on their downstream
face.
4.5 Mass movement
Mass movement landforms and deposits are of national or international importance for:
•
•
•
•
the largest landslides in Britain;
great variety of mass movement types
what the spatial distribution, age, magnitude and type of mass movements can tell us
about changing environmental conditions since deglaciation;
relationships between some of the largest mass movements (rock slope failures) and
glaciation.
Page 59
10 January, 2002
4.5.1 Mass movement types and causes
Mass movement processes are responsible for the downslope movement of material under
gravitational forces, occurring as either dry falls and topples (such as rock falls) or flows and
slides of wet-to-saturated mixtures of rock and/or soil debris, which may occasionally
include ice crystals. Although often colloquially referred to as ‘landslides’, very few types of
mass movement only involve sliding. Various classifications of mass movement processes
and their resultant landforms exist, and a simplified classification is presented in Table 4a.
Table 4a
Varne’s classification of mass movements in bedrock, coarse debris and finer soils
Type of movement
Falls
Topples
Slides
(a) Rotational
(b) Translational
Lateral spreads
Flows
(a) in bedrock
(b) in soil
Complex
Mass in motion travels most of the distance through the air. Includes
free fall, movement by leaps and bounds and rolling of fragments of
rock or soil.
Over-turning movement about a pivot point below the centre of
gravity of the mass. Unchecked this leads to falls and slides.
Movement involves shear displacement along one or more surfaces or
within a narrow shear zone.
Movement due to forces that cause a turning movement about a point
above the centre of gravity of the mass. Surface of rupture concave
upward.
Movement along a flat or gently undulating surface. Movement occurs
along a line of weakness, such as a bedding plain, joint of fault.
Distributed lateral extension movements in a fractured mass.
Very slow deformation of bedrock and or deep creep of rock
structures.
Rapid to very slow creep in soil, resulting in fluid-like flow structures in
the debris. Boundary between mobile and static soil may be sharp.
Many mass movement landforms are formed by a succession of mass
movement events, comprising for example an initial translational slide,
fluidisation and then flow of debris and water as in commonly occurring
hillslope debris flows in the Highlands.
Source: based on Brunsden and Prior (1984).
All downslope movements of rock or soil require the right conditions (or pre-conditioning)
and an environmental trigger that reduces the strength of slope materials so that they are
no longer able to resist gravitational forces. There are a number of ways in which this can
occur in bedrock and soils; these can be divided into external causes and internal causes of
instability (Hansen, 1984).
External changes in instability conditions:
1. Undercutting of the toe of the slope, e.g. caused by quarrying or river or coastal
erosion.
2. Unloading (removal of overburden) e.g. caused by quarrying, natural erosion processes,
long term isostatic recovery.
Page 60
10 January, 2002
3. Loading (addition of overburden, increased height), including undrained loading (where,
for example, rockfall debris lands on a water-saturated slope and triggers further slope
failure where the rocks impact).
4. Shocks and vibrations (e.g. earth tremors) which can lead to a variety of processes that
include liquefaction, remoulding, fluidisation, and cohesionless grainflow, all of which can
occur on relatively shallow gradient slopes.
5. Drawdown (lowering of the water-table) e.g. during climate change.
6. Changes in water regime (e.g. extreme events such as large snowmelts, intense
rainstorms and prolonged wet weather, all of which increase pore water pressures
within the slope).
Internal changes in stability conditions:
7. Progressive failure (following lateral expansion or fissuring and erosion).
8. Weathering (freeze-thaw, desiccation, reduction of cohesion, removal of cement).
9. Seepage erosion (solution, piping).
4.5.2 Documented mass movements in Scotland
The geological variety and glacial legacy of the Scottish upland landscape has provided
conditions where a wide range of different types of mass movement are represented.
Research into mass movements in Scotland has been limited, with the full extent of the
resource largely under-documented. One study only recorded documented mass
movements in Scotland, and is summarised in Table 4b and in Figure 9. It should be noted
that these figures greatly under-represent the total numbers of features, particularly among
very widespread phenomena such as debris flows and rockfall talus (scree).
Table 4b
Summary of documented mass movements in Scotland by area
Mass
movement
medium
Mass
movement
type
Grampian
Highlands
NW
Highlands
Scottish
Islands
Rock
Rock
Rock
Rock
Rockfall
Rock topple
Rock sag
Translational
slide
Rotational Slide
Complex
Undifferentiated
All types
2
7
18
35
3
7
11
19
5
27
213
302
3
10
140
193
Translational
slide
Debris flow
Complex
Undifferentiated
All types
18
2
20
11
20
68
10
Rock
Rock
Rock
Rock
Drift
Drift
Drift
Drift
Drift
12
Midland
Valley
Southern
Uplands
Total
3
1
10
14
29
58
16
5
40
1
6
29
69
20
48
446
24
2
1
3
24
37
1
21
2
1
18
22
34
13
47
115
9
9
Source: Ballantyne (1986).
Page 61
10 January, 2002
For example, in the Grampian Highlands only 20 cases of debris flow are recorded, but as
many individual flows can be found on single hillsides, such as in Glen Coe or in the Lairig
Ghru in the Cairngorm Mountains.
Falls are abrupt free-fall movements of material, in bulk or block form, away from steep
slopes such as cliffs. Rockfalls are common on the glacially steepened cliffs of the Highlands.
Most single or small rockfall events gradually build up rockfall talus (scree) slopes. However,
some massive falls of whole sections of cliff have occurred (e.g. Shelter Stone, Cairngorm
Mountains; Lost Valley, Glencoe; Glen Pean), which can lead to flow of the falling rock
debris to form rock avalanche deposits, such as the bouldery deposits found below Beinn
Alligin in Torridon, and in the Campsie Fells near Strathblane.
Toppling rocks are more common in bedded or strongly foliated rocks (such as sedimentary
sandstones and shales, and metamorphic schists), but are also found in granites and lavas.
Examples include crags around the Lairig Ghru in the Cairngorm Mountains above a
rock–glacier complex. Toppling may commonly develop downslope through sliding and
falling into more complex mass movement features. At Carn Mor, Glen Pean, foliated schists
dipping out of the hillside have been toppled down the steep hillside (over 40º).
Slides usually involve the material sliding or slumping along recognisable failure or slip planes.
The type of landslide that characterises the Trotternish rotational landslides in Skye extends
continuously along the foot of the basalt cliffs for some 23 km and forms the best example
of landsliding in the whole of Great Britain. These landforms are a result of foundering at
the depth of weaker Jurassic sedimentary rocks (shales, sandstones and limestones) that are
sandwiched between a 300-m-thick accumulation of Tertiary flood basalts and dolerite sills
which were intruded into the Jurassic sediments during the Eocene. Motion was probably
initiated during the Late Tertiary (ending some 2.5 million years ago) as a result of tilting and
faulting of the whole area. The most recent failure of up to 600 m of cliff occurred 6500
years ago, forming the Old Man of Storr. Earlier mass movement blocks further downslope
have been rounded and moulded by the passage of the last ice sheet. This type of failure
produces a classic assemblage of slide blocks which can be back-tilted towards the scarp
face along an ‘inward’ (towards the foot of the scarp) dipping failure plane.
Page 62
10 January, 2002
Figure 9
Distribution of documented rock slope failures (from Ballantyne, 1986). (Reproduced
by permission of the Royal Scottish Geographical Society from Scottish Geographical
Magazine, 102 (1986), pp. 134–50.)
Flows Debris is defined as a collection of rock, earth and other inorganic material that has
been moved from an original site by streams or mass movement processes and redeposited
at another locality. The downslope movement of this material, mixed with minor quantities
of clay, entrained water and air is known as a debris flow. Debris flows commonly consist of
fluidised lobes of poorly sorted coarse and fine sediments sourced from debris-covered
hillslopes. As the material progresses downslope, low ridges and levees (overbank deposits)
accumulate on either side of its track (the main path of the flow). Debris flows are common
Page 63
10 January, 2002
throughout the Highlands. Some of the best examples are in the Cairngorms, Drumochter
Pass, Glencoe and Glen Dochart. Repeated debris flows, for example, rattling down an
erosion-susceptible faulted gully at Achtriochtan in Glencoe have built one of the biggest
and most active debris cones found in Britain. In the past, debris flows down the cone
buried a small settlement, and, more recently, periodically block the A82. Solifluction is the
slow downslope flowage, over gentle slopes, of masses of fine-grained, surface waste (for
example soil or weathered sediment) saturated with water. It is most effective in periglacial
environments (see Section 4.2.3), where freeze–thaw processes in the active top layer of
the soil produce sufficient water to assist in the downslope movement of the material
(gelifluction). It produces faster rates of downslope movement than soil creep. Solifluction is
common in the uplands where both relict and active forms occur. Gelifluction sheets and
lobes are spectacularly developed on mountain masses such as Cairngorms, Creag Meagaidh
and Lochnagar; and solifluction terraces, on the Fannichs and An Teallach. Also, relict
examples occur in the lowlands where sheets of soliflucted debris mantle many slopes (e.g.
in Buchan) and in areas outside the Loch Lomond Readvance. Slope failures also occur on
snow-covered slopes, producing a variety of different types of Snow Avalanche, which can
modify and build distinctive slope landforms, such as avalanche boulder tongues. See also
Section 4.2.3 (Periglacial landforms).
Complex There are over 600 documented examples (Ballantyne, 1986) of large rock slope
failures, where whole mountainsides are gradually slumping. These are most common in
layered rocks such as schists. Evidence for large-scale rock slope failures includes cracks
(large enough to climb into) running along mountain ridges and across spurs (e.g. behind the
headwall of Corrie Brandy, Glen Clova), marking the upper edge of failure of bedrock deep
within the slope. Lower down, the slope has the appearance of crumpled rock, comprising
successive outcrops of the layers of rock moving intermittently down slope. Examples occur
principally in schistose rocks (Figure 8). Some of the biggest examples have probably been
intermittently on the move since the ice melted. At Ben Attow, Kintail, outward moving of
the rock slope has resulted in numerous back (up-hill facing) scarps up to 10 m high running
across an area of 2.2 km2 of hillside.
4.6 Caves and karst
The cave and karst landforms and deposits in Scotland are of national importance for:
•
•
glaciokarst features;
the fossil remains preserved in the ‘Bone Caves’ at Inchnadamph.
Caves and karst form a relatively minor part of the geomorphology of Scotland, although
locally they are significant for their unique records of landscape evolution and
palaeoenvironmental change and for the associated soils and habitats they support.
Limestone pavement is a very scarce habitat covering less than 3,000 hectares in the United
Kingdom, only about 10% of which is in Scotland. Only in Assynt are there relatively
extensive cave systems, including the longest cave system in Scotland, pavements, surface
solutional features glaciokarst features and dry valleys, all developed in dolomites of the
Durness Group of Cambrian and Ordovician age. The Assynt caves are also notable for the
preservation of the remains of ice age fossil vertebrates. Elsewhere, the outcrops of various
limestones are restricted in extent, e.g. around Durness, on Skye, in Applecross, in Glen
Creran and at various sites in Perth and Kinross.
Page 64
10 January, 2002
An exhaustive survey of British limestone pavements by Ward and Evans (1975) recorded
17 pavements in Scotland, covering 221 hectares. This compared with 497 pavements
covering 1893 hectares in England and 23 pavements covering 36 hectares in Wales. The
data for Scotland were known to be incomplete. More recently, S.D. Ward (pers. comm.)
has collated observations of limestone pavements at 23 localities in Scotland, although some
of these are believed to be small fragments.
Of particular interest, compared with the pavements of England and Wales which occur on
rocks of Carboniferous age, those of Scotland occur on two other rock formations. The
first is the Durness limestone, which runs north from the Isle of Skye to Durness on the
north coast of Highland. Pavements have been formed in Strath Suardal (Skye), Rassal (also
known as Glas Cnoc), Inchnadamph and at Durness itself. The second is the Dalradian
limestone, which crops out intermittently from the Isle of Lismore in the Firth of Lorne to
Portsoy on the Moray coast of Aberdeenshire. Fragments of pavements on the Dalradian
occur, for example, on Schiehallion.
Page 65
10 January, 2002
5
Soils
The soils of Scotland are of national or international importance for the following features:
•
•
•
•
•
•
peat and organic soils;
alpine/subalpine soils;
anthropogenic soils;
interstadial and interglacial palaeosols;
soils formed on distinctive parent materials (e.g. machair, serpentine);
unique podzols (iron and humus podzols) of very limited spatial extent
Soils are an intimate mixture of mineral matter and organic matter with spaces between the
particles containing air, water and micro-organisms. The structure of cracks and voids and
the presence of organic matter transforms soil from unconsolidated debris into a dynamic,
living environment for micro-organisms, plants and animals. There are many different types
of soil, characterised by depth, composition and appearance, with differing physical, chemical
and biological properties. Soil is not only a reservoir of nutrients and water, but serves as a
large, long-term pool of carbon stored as dead organic matter. Soil is also an archive of
environmental conditions and human activity.
Although a small number of interglacial and interstadial palaeosols are locally preserved in
Quaternary deposits, soil development in Scotland was initiated between about 15,000 and
10,000 years ago, at the end of the last ice age. The retreating ice sheets revealed a newly
exposed landscape of glacial drifts that, over most of the country, masked the underlying
rocks. This largely barren land surface was gradually transformed as climatic conditions
improved. The first colonising plants would have grown directly on this bare, unconsolidated
material. Over time, by physical and chemical weathering and the action of soil organisms,
glacial drift was transformed to form soil and so improving conditions for subsequent plant
colonisation. The establishment of more deeply rooted plants, which were able to retrieve
nutrients and water from depth, served as initial sources of organic matter along with
lichens, mosses and algae. The accumulation of plant debris provided more favourable
conditions for micro-organisms, thereby further improving soil fertility and soil structure.
Over thousands of years Scottish soils have thus developed, except where harsh conditions
prevented the formation of anything but the most immature soils, such as on mountain tops
and along exposed coasts.
Scotland’s range of soils is the result of variations in parent material, climate, topography
and time of soil development. Most soils have been modified by human influence through
agricultural activities. Soil horizons, if preserved, are a reflection of the present and former
environmental conditions which have led to soil formation. The profile of a soil is
characterised by decreasing organic content and biological activity with depth, together with
an increasing resemblance to the underlying parent material from which the soil was
formed. The two most important factors which have influenced soil properties in Scotland
are the nature of drift parent materials and associated periglacial action and human activity.
5.1 Scottish soil types
The soils of Scotland can be broadly divided into four main groups: peats, gleys, podzols and
brown forest soils (Figure 10). Soils are not discrete entities but form a continuum across
Page 66
10 January, 2002
the landsurface, which results in a wide variety of different soil types within these four main
groups as a result of changes in one or more of the five principal controlling factors of soil
formation and the influence of human activity.
Over much of the Western Isles, northern Scotland and the Highlands, wet and cold
conditions suppress biological activity in soils. Plant debris accumulates faster than it can be
decomposed, and anaerobic, waterlogged conditions result in peat formation across wide
areas. This store of organic matter represents a huge reserve of terrestrial carbon, much
higher than that contained within above-ground vegetation. It is estimated that 71% of the
UK soil carbon reserves are contained within Scottish soils, which represents a carbon pool
which far exceeds that of the whole of the above-ground biomass.
At lower elevations, with lower rainfall and higher temperatures, microbial activity increases
sufficiently to allow soil processes to accelerate, although there is still some surface organic
accumulation. ‘Gleys’ develop on fine-textured parent material with poor drainage, resulting
in intermittent or semi-permanent waterlogging. Under anaerobic conditions, iron and other
compounds in the soil become mobile and this is exhibited as mottled grey, blue-green and
rust colours. Also, decomposition of organic matter is slow, resulting in the acculation of
organic matter or shallow peat in many of these soils.
In the drier east, parent materials are often acidic and coarse grained. Podzols and their
derivatives are the dominant soil types. Acidic conditions suppress biological activity,
allowing surface organic accumulation. Their coarse sandy texture means that these soils are
well drained, and, under acid conditions, organic and mineral compounds are rapidly leached
from the upper horizons. This produces a distinctive profile of abruptly different horizons
with dark, surface organic accumulation; a coarse-grained, bleached and leached upper
horizon; and a dark-brown lower horizon where the leached minerals are re-deposited.
Separating the leaching and the re-deposition zones is often a dark layer of organic
accumulation, composed of material washed down from the surface, or in some instances an
‘iron pan’ (layer of iron oxide accumulation). Podzols and gleys are the most widespread and
diverse group of soils in Scotland, displaying distinctive characteristics dependent upon site
conditions.
In the south-west of Scotland, peaty and gley soils dominate. In the south-east, where
conditions are drier, brown forest soils are represented. These form on a variety of parent
materials but their key soil-forming characteristics are moderate to low acidity, low rainfall
and warm temperatures. Such conditions encourage biological activity and consequently
organic matter is efficiently broken down, producing deep, well-mixed, fertile soils with
abundant earthworm activity. These are the soils most favoured for agriculture.
As human settlement developed in Scotland, soils were modified and exploited, for instance
by forest clearance and then later by land preparation for new tree planting, or for
agricultural production through drainage and cultivation. Human influence on soils is now so
widespread that it impinges, to greater or lesser degrees, on all soils in Scotland. Even in the
Highlands, soils have been modified by forest clearance and grazing and in some cases arable
cultivation. At present over 50% of the land area of Scotland is composed of soils with
highly organic surface horizons that support ecosystems of natural heritage importance.
Page 67
10 January, 2002
Figure 10
Page 68
Generalised map of soil types (copyright The Macaulay Institute 2002. Reproduced
with permission).
10 January, 2002
6
Scotland’s role in the history of
geology and geomorphology
Since the birth of modern geological science, with the pioneering work of the Scottish
geologist James Hutton (McIntyre and McKirdy, 1997), Scotland has formed a natural
laboratory in which many of the fundamental principles of the Earth sciences have been
developed. The lessons learned have been applied worldwide. Areas such as the NW
Highlands, Glen Coe, Rum and Arthur’s Seat have all provided crucial evidence for past
geological processes and allowed modern applications. In the NW Highlands and Western
Isles the work of Sutton and Watson (1951) on the Lewisian Complex laid much of the
groundwork for unravelling the geological history of poly-deformed gneissic terrains. Peach
et al. (1907) first described the Moine Thrust, the most famous of the major Caledonian
structures, and its significance for large-scale, higher-level crustal deformations. Geological
mapping of the Glen Coe area, early in the twentieth century, revealed volcanic rocks of
Devonian age attributable to cauldron subsidence, the first example of this type of
volcanicity to be identified and described in the geological record (Clough et al., 1909). The
Tertiary volcanic geology of Rum has yielded much information on the processes taking
place in the environment of the magma chamber, with the development of theories relating
to the origin of layering in igneous rocks (e.g. Wager and Brown, 1968). The Arthur’s Seat
volcanic complex in Edinburgh provided key evidence supporting the theories of James
Hutton, which laid the foundations for the development of modern geology. Arthur’s Seat is
still regarded as perhaps the best example on Earth of a dissected ancient volcanic cone.
The significance of Scottish palaeontology became widely evident following the publication
of a monograph by the Swiss geologist Louis Agassiz on the fossil fishes of the Old Red
Sandstone. Subsequently, with the popularisation of geology and palaeontology by Hugh
Miller, the general public became aware of the remarkable fish remains of the Scottish
rocks. It is perhaps because of Hugh Miller that interest in Scottish palaeontology was
awakened in the decades succeeding his work The Old Red Sandstone in 1841. Much of the
early work on Scottish fossils was undertaken by self-taught amateurs, such as Robert Dick
of Thurso, Robert Slimon of Lesmahagow and the Reverend Doctor Gordon of Elgin. The
Geological Societies of Glasgow and Edinburgh acted as focal points for amateur collectors
and as vehicles for discussion, publication and dissemination of information. During the last
150 years the main thrust in palaeontology has been on discovery and description. Although
this continues today, there has been a shift of emphasis and the ecology, environmental
controls and tectonic settings of fossil biotas are increasingly receiving attention.
Scotland also played an important role in the development of the glacial theory in the
nineteenth century. This was most effectively promoted by the Swiss geologist Louis
Agassiz, who clarified and tested his ideas in Scotland in the West Highlands, notably in the
Glen Roy area, and in Edinburgh. The glacial theory was embraced by Scottish geologists, a
number of whom, including Charles Maclaren, Thomas Jamieson, the Geikie brothers, James
Croll, James Forbes and Andrew Ramsey, contributed significantly to its development and
application based on the field evidence from Scottish sites (Davies, 1968; Gordon, 1997).
Page 69
10 January, 2002
7
Knowledge and state of the
resource
7.1 National datasets
National datasets exist for geology and soils. The former is in the form of maps and
memoirs published by the British Geological Survey (BGS). The latter is in the form of maps
and memoirs on the soils of Scotland published by the Soil Survey for Scotland, now part of
MLURI. The primary aim of the national 1:250,000 reconnaissance soil maps of Scotland was
to evaluate agricultural potential.
Although individual sites and areas have been studied in varying degrees of detail, there has
been no systematic, comprehensive national inventory of geomorphological interests similar
to the geological mapping undertaken by BGS. However, national inventories have been
undertaken for Scottish beaches by Aberdeen University for the former Countryside
Commission for Scotland (summarised by Ritchie and Mather, 1984) and for landslides as
part of a DoE survey (Ballantyne, 1986).
The Geological Conservation Review (GCR) is a site-based inventory of the most important
sites for geology and geomorphology in Great Britain (Ellis et al., 1996). There are over 800
GCR site interests in Scotland (Table 5). Because of overlaps, these are encapsulated in
some 500 SSSIs (sites of special scientific interest) or potential SSSIs. Scientific results of the
GCR are being published in a series of 42 volumes by the Joint Nature Conservation
Committee (Ellis et al., 1996). Each Earth science SSSI in Scotland is also being documented
separately by SNH in a series of Earth Science Site Documentation Reports. These include
information for management and monitoring.
Table 5
Summary of GCR sites in Scotland
Subject areas
Number of sites
Stratigraphy
Structural and Metamorphic
Igneous Petrology
Mineralogy
Palaeontology
Quaternary
Geomorphology
Total
135
193
162
47
84
136
77
834
Although soils were not considered in the GCR, representative examples of most of the
important soils types in Scotland occur in existing SSSIs (Gauld and Bell, 1997).
Sites outwith the GCR provide the context for the GCR site networks and also form a
significant component of the wider Earth heritage. However, there is no standard
documentation of information or survey for such sites.
Page 70
10 January, 2002
The data sources that are currently available and the state of knowledge about our Earth
heritage are outlined in the following sections.
7.2 Geology and palaeontology
7.2.1 Knowledge
•
•
Well covered by BGS maps and memoirs and in journal articles and theses.
Regional inventories covering Orkney (NCC, 1978), Shetland (NCC, 1976) and the
Outer Hebrides (NCC, 1977) list, map and describe most sites of geological interest for
conservation in these areas. However these reports are now dated.
7.2.2 State and quality
•
•
Systematic information on state and quality (e.g. degradation of exposures) is confined
to SSSIs as reported in individual Earth Science Site Documentation Reports, which
were completed for the entire SSSI series in 2001; these reports will provide a baseline
for site condition monitoring.
A site condition-monitoring programme is being implemented for SSSIs with a 6-year
monitoring cycle.
7.3 Geomorphology
7.3.1 Knowledge
•
•
•
•
•
•
Poor understanding of spatial distributions, with no systematic inventory of landforms or
process systems; exceptions are The Beaches of Scotland reports (Annex 1) and landslides
survey (Section 4.5); GCR site networks provide partial and selective inventories of
known key features only.
Regional reports covering Orkney (NCC, 1978), Shetland (NCC, 1976) and the Outer
Hebrides (NCC, 1977) list, map and describe all sites of geomorphological interest in
these areas.
Distribution of coastal landforms can be inferred from inventories and distribution maps
produced for coastal habitats (e.g. Sand-dune Vegetation Survey of Great Britain,
Saltmarsh Survey of Great Britain), although correlation between landform and habitat is
not perfect.
Knowledge of process systems (e.g. sediment transport) is patchy; reviews of coastal
processes are contained in 11 regional, and one overview, report on the Coastal Cells
of Scotland (Annex 2); more detailed studies of coastal processes are typically restricted
to areas with significant erosion concerns where Shoreline Management Plans or
Shoreline Assessments have been prepared (Annex 3).
Knowledge of magnitude, rate and frequency of change are limited to individual case
studies of coastal and river systems (e.g. Tentsmuir et al., 1996; Gemmell et al., 2000).
Summary statistics are contained in The Beaches of Scotland overview report (Ritchie and
Mather, 1984) on a region by region basis of the proportion of beaches eroding, stable
or advancing when surveyed. Rates of change were not quantified and the survey has not
been repeated.
Page 71
10 January, 2002
7.3.2 State and quality
•
•
•
•
Beaches of Scotland (Ritchie and Mather, 1984) and Beaches of the Highlands and Islands of
Scotland (Mather and Ritchie, 1977) overviews contain statistical summaries of adverse
features (e.g. over-trampling, sand extraction) affecting beaches.
Beaches of the Highlands and Islands of Scotland (Mather and Ritchie, 1977) ranks and
tabulates beach complexes of highest geomorphological interest in the Highlands and
Islands.
Systematic information on state and quality is confined to SSSIs as reported in individual
Earth Science Site Documentation Reports which were completed for the entire SSSI
series in 2001; these reports will provide a baseline for site condition monitoring.
A site condition-monitoring programme is being implemented for SSSIs with a 6-year
monitoring cycle.
7.4 Soils
7.4.1 Knowledge
•
•
Physical and chemical aspects are covered at reconnaissance level [Soil Survey of
Scotland 1:250,000 series of maps and memoirs and National Soils Inventory (NSI);
MLURI], but updating is required; North East Coastal area and Central Belt covered at a
higher resolution for land capability purposes, including ad hoc maps and memoirs.
Poor knowledge of soil biology/biodiversity/biological functions (although Sourhope has
perhaps the most intensively studied soil in the world).
7.4.2 State and quality
•
•
•
Systematic information available on acidification critical loads.
Existing information on state and quality of soils in Scotland and assessment of impacts
of human activities is reviewed by SEPA (2001) in State of the Environment. Soil Quality
Report.
Very few monitoring studies undertaken, and no systematic framework for monitoring
key indicators of quality or change.
Page 72
10 January, 2002
8
Trends
8.1 Trends in coastal evolution
Long-term trends in coastal evolution at the millennial scale since the end of the last Ice Age
c. 15,000 years ago have been documented in many studies of raised beach landforms and
deposits, raised estuarine deposits and intertidal and nearshore deposits (see Section 5.2.5).
These are reviewed, for example, in Sissons (1976), Sutherland (1984), Gordon and
Sutherland (1993), Shennan et al. (1995), Smith (1997) and Smith et al. (2000).
More recent changes over the last century or so have been documented at a number of
sites (Table 6).
Table 6
Documented coastal changes
Site
Changes
Source
Spey Bay
Average annual rate of growth
of active shingle beach of 33.6
ma–1, AD 1870–1995
Average annual rate of spit
extension of 22.3 ma–1 at
Buckie Loch, AD 1870–1988;
average annual rate of spit
extension at the Bar, AD
1878–1988
Dune and machair erosion
rates of up to 100 m over the
period c. 1975–1998
Annual rates of dune recession
of up to 2 m, 1965–1997
Detailed patterns of coastal
progradation and erosion
Seaward advance of coastal
edge by up to 500 m since AD
1812
Gemmell et al. (1996)
Culbin Sands
Coll and Tiree
Montrose
Morrich More
Tentsmuir
Comber et al. (1994)
Dawson (1999)
Angus Council (1998)
Hansom and Leafe (1990)
Hansom and Black (1996)
McManus and Wal (1996)
8.2 Trends in river channel change
Long-term trends in river channel and floodplain evolution at the millennial scale since the
end of the last Ice Age c. 15,000 years ago have been documented at relatively few sites, the
most notable being the River Feshie (Werritty and Brazier, 1991) and the North Esk/West
Water (Maizels and Aitken, 1991).
Changes over shorter timescales have been documented for a number of sites, including the
River Feshie (Werritty and Brazier, 1991), the River Clyde (Rowan et al., 1989; Brazier et al.,
1993), the River Dee (McEwen, 1989) and the River Spey (Gemmell et al., 1996). An analysis
of changes in river channel planform over the last 150 years was undertaken by Leys (1997)
using 10 reaches from some of the most dynamic rivers in Scotland. This analysis used
Page 73
10 January, 2002
historical maps, plans, aerial photographs and literature sources to identify channel changes
and its possible causes. Identifying periods of increased or reduced channel activity within
the last 150 years is complicated by the different frequencies with which planform mapping
(aerial photographs, maps and plans) is undertaken and the different intervals between
mappings that result. This makes identifying an average rate of change or a common period
for analysis of change very difficult. A low frequency of mapping also affects the probability
that a short-lived change will be detected or easily related to the causal factor. Although the
historical approach has limits and difficulties, it provides a mechanism for the analysis of past
changes which, because of the dynamic nature of the system, are no longer visible in the
landscape record.
Leys (1997) identified that there were very broad spatial patterns in the rate of channel
activity, and that rivers across Scotland were not increasing or decreasing their rate of
activity simultaneously. Werritty and Leys (2001) suggest that these patterns may relate to
fluctuations in climate, and particularly to the documented phenomenon of ‘flood-poor and
flood-rich’ periods within the hydrological record. The 1980s, for example, were a relatively
flood-rich period (Steel et al., 1999), and periods of increased channel and floodplain
reworking were reported across the country from the Borders to Moray (although within
this broad pattern there was significant local variation). This increased activity did not,
however, result in major or significant changes to channel behaviour which were outwith
those changes seen at other times in the historical record. Indeed, this historical analysis
indicates that the behaviour of these 10 sites over the period of study has generally been
robust, and that the rivers have not changed behaviour significantly (or any changes have not
persisted), despite the occurrence of some large and significant flood events which locally
changed channel form.
The analysis undertaken by Leys (1997) and those analyses previously undertaken, for
example by McEwen (1986), illustrated that there is significant spatial variability in channel
response across Scotland. Factors such as the local geology, vegetation cover, extent of
human interference and the valley floor setting appear to be very significant in influencing
channel activity. Temporal variability at a site is often coincident with or subsequent to flood
events. Several sites show channel planform changes that would be consistent with the
passage of a sediment wave (Hoey, 1992) through the system. Changes in flood frequency
or magnitude, as suggested under current climate change scenarios, could significantly alter
both channel behaviour and the natural capacity of the system to recover. Alteration to the
natural system, for example through significant human intervention, could impair the
system’s ability to undertake channel recovery. Examples of this reduction in capacity to
absorb change was seen in the historical record.
8.3 Mass movements as environmental indicators
Mass movement deposits and associated landforms provide valuable information about the
changing state of health of the landscape. All mass movements occur when the strength of
the rock or soil on a hillside is overcome by the force of gravity. Weaknesses in the rock
such as bedding planes and joints sloping in the same direction as the slope, quarrying and
even previous landslides and the undermining of the foot of the slope by glaciers make
failure more likely. A key factor in triggering slope failure is the movement and pressure of
water within the rock and soil and the type and extent of vegetation cover. The most
common modern small to medium-sized slope failures (debris flows and slides) in Scotland
Page 74
10 January, 2002
are usually triggered by extreme weather events such as intense rainstorms, which rapidly
saturate the ground weakening and loading the soil or rock.
Scotland rarely experiences hazardous mass movement. But changes over time in the type,
size and number of mass movements occurring in one area can indicate significant
environmental changes of climatic and/or human origin. Case studies of debris flows include
those in Glen Coe (Innes, 1983), Glen Etive (Brazier et al., 1988), Glen Feshie (Brazier and
Ballantyne, 1989), Trotternish (Hinchliffe, 1999) and Glen Docherty (Curry, 2000).
Studies of debris flows allow the factors which caused them to be analysed. In some cases
there is a clear association between, for example, forest clearance during historical times
and changes in slope stability (Brazier et al., 1988). However, there are other examples of
debris flow deposits where land use cannot have played a part in promoting slope failure,
but reflect favourable local geological conditions and storm frequency (Brazier and
Ballantyne, 1989; Hinchliffe, 1999). The complexity in the relationship between land use and
climate change and landscape sensitivity remains a crucial area of modern landslide research
in Scotland.
Page 75
10 January, 2002
9
Pressures and threats
The pressures and threats facing our Earth heritage across Scotland are diverse but are
largely generated by population and development pressures. The standard list of Potentially
Damaging Operations used in SSSI designation provides an indication of the common
operations likely to damage the resource.
At the outset, it is important to distinguish between relict and active features. The former,
once damaged or destroyed, cannot easily be reinstated or recreated since the formative
processes are no longer active; the latter may in certain circumstances be able to self-repair
(or at least re-form to be similar) and therefore may be more robust. An important concept
in evaluating change is that of geomorphic sensitivity, which reflects both the propensity of
the system to respond to, and its capacity to absorb, an externally imposed change. In order
to evaluate trends and threats, it is necessary to examine the sensitivity of geomorphological
systems to both natural processes and human activity, and also to examine the factors that
condition their responses. In general, relict features are more sensitive to development
pressures than active features since relict features cannot re-form once damaged.
The pressures, threats, impacts and trends seen in the Earth heritage resource of Scotland
are discussed in more detail (where the information exists) for each zone in Part 2. Here
the main issues are highlighted.
9.1 Pressures and impacts
Pressures on Earth heritage sites may result in a number of general types of impact (Table
7). There may be physical loss, where features of interest are removed (e.g. quarrying for
minerals, sand and gravel and fossils, removal of topsoil etc.), or damaged in situ (e.g. river
engineering, levelling of features to enable building, etc.). In some cases, features may be
obscured (e.g. by vegetation or development). In other cases, natural processes may be
disrupted (e.g. through installation of coast defences), static features may be destabilised
(e.g. through over-grazing of sand dunes) or active features may be ‘fossilised’ (e.g. gravel
bars in a river if discharges are reduced). Although many ‘obscuring’ developments have
relatively long project lifespans, benign development can occasionally act to protect the
underlying feature from removal. In soils and rivers, obscuring development can lead to
unwanted changes in the nature of the soil (e.g. through altering vegetation cover, etc.) and
in the habitats and species within the channel. The impact of particular threats is not
restricted solely to on-site effects. Some threats (e.g. river engineering) alter the natural
processes and thus produce off-site (particularly downstream) effects. Many of the
pressures and impacts that occur across Scotland are discussed in Gordon and Leys (2001)
and are summarised in Table 8; other important issues are summarised below:
•
•
There are generally no systematic surveys or national assessments of pressures, impacts
and how the resource is changing (this combines with a lack of systematic survey on the
distribution and extent of features, see Section 7), although evidence of potentially
damaging activities affecting Scotland’s beaches was recorded fairly systematically
through the 1970s (Mather and Ritchie 1977; Ritchie and Mather 1984).
For static or relict features, impacts and sensitivities are clear; informal guidelines are
available for assessment of sensitivity and vulnerability but the main issues relating to
static and relict features are ones of policy, e.g. site integrity.
Page 76
10 January, 2002
•
•
For active systems, it is much more difficult to establish quantitative links both on-site
and off-site; geomorphological sensitivity and singularity complicate the issue, and the
existence of thresholds for change and system feedbacks make identifying cause and
response extremely hard.
Soil changes are very difficult to determine as soils are not explicitly protected or
monitored and hence data on the nature of the resource and its condition are
unavailable for Scotland. Issues which affect soils, although not quantified or monitored,
include contamination, erosion, acidification and loss of organic material. Significantly,
loss of soil material is non-reversible in human timescales.
Baseline surveys of a range of geomorphological systems are required, with subsequent
regular monitoring of selected indicator variables. Analysis of palaeoenvironmental records
will allow current change to be placed in a longer time perspective as well as an evaluation
of process rates, magnitude–frequency relationships and the stability of particular systems
over different timescales.
The resource is under pressure at both site-specific and wider landscape scales from a range
of human impacts; these are discussed elsewhere both in general terms and in relation to
specific localities (e.g. Werritty and Brazier, 1991; Gordon and Campbell, 1992; Werritty et
al., 1994; Taylor, 1995; Taylor et al., 1996). The more dynamic elements of the landscape are
also subject to natural perturbations of varying frequency and magnitude which produce
responses in the landforms and sediments. It is generally not easy to decouple the effects of
natural change and human impacts (e.g. Ballantyne, 1991).
At present it is difficult to draw clear conclusions about trends in the state of the resource.
This arises from the lack of (1) a basic resource inventory, (2) systematic monitoring of the
condition of statutory and non-statutory sites and (3) geomorphological process monitoring.
Table 7
Categorisation of on-site impacts
Impacts on rocks, fossils and landforms
Impacts on soils
•
Physical loss
•
Physical loss (erosion) or burial of soil
•
Fragmentation involving loss of integrity,
context and interrelationships between
landforms or exposures
•
Physical damage to soil structure
•
Loss of visibility
•
Impairment of soil functions (e.g. through
pollution, acidification, loss of or reduction
in soil biodiversity)
•
Alteration or disruption of natural
processes/system dynamics
•
Loss of naturalness
•
Change of state of static or dynamic features
(e.g. activation or fossilization)
Page 77
10 January, 2002
Table 8
Pressures and impacts on Earth science features
Pressure
Examples of on-site impacts1
Examples of off-site impacts2
1. Mineral extraction
(includes pits,
quarries, opencast
and extraction of
aggregate from
rivers, dunes and
beaches)
•
•
•
•
•
•
•
Destruction of landforms and
sediment records
Disruption of natural processes
Destabilisation of dunes
Erosion, mixing and compaction of
soils
may have positive benefits in creating
new sedimentary sections
Soil contamination
•
•
•
•
•
Contamination of
watercourses
changes in sediment supply
to active process systems,
leading to deposition or
channel scour
beach draw-down and
erosion of coastal edge
Reduced sediment supply
down-drift
Disruption of drainage
network (impacts on run-off)
Dust or windborn soil
particles
2. Restoration of
pits and quarries
•
•
Loss of exposures
Loss of natural landform
•
Habitat creation
3. Landfill
•
•
•
•
•
•
Loss of geological exposures
Loss of natural landform
Over-stabilisation of dune systems
Soil contamination and loss
Contamination of water courses
Contamination of groundwater
•
Detrimental effects of gases
and other decomposition
products on surrounding
soils
re-exposure and
redistribution of landfill
material in eroding
beach/dune system
4. Reclamation of
contaminated land
•
Improvement of soil quality
•
Leakage of contaminants to
water courses or ground
water
5. Commercial and
industrial
developments
•
Large-scale damage and
disruption/loss of surface and subsurface features, including landforms
and soils
Stabilisation of naturally dynamic
landforms
Disruption of natural drainage
patterns (e.g. on saltmarshes)
Soil contamination
Damage to soil structure
Changes to soil water regime
Loss of soil and biodiversity
•
Changes to
geomorphological processes
downstream, arising from
channelisation or water
abstraction
Disruption of sediment
supply alongshore and
impacts on local
hydrodynamics
Leakage of contaminants to
water courses or
groundwater
•
•
•
•
•
•
Page 78
•
•
•
10 January, 2002
6. Coast protection
•
•
•
•
•
7. River management
and engineering
•
•
•
8. Afforestation
•
•
•
•
•
9. Agriculture and
grazing of livestock
•
•
•
•
•
10. Other land
management
changes (e.g.
drainage, dumping,
construction of
tracks)
•
•
•
•
•
Page 79
Loss of coastal exposures
Destruction of active and relict
landforms
Stabilisation of naturally dynamic
landforms (sand dunes)
Reduction in sediment supply to
beach and consequent beach
lowering
Prevention of landward transgression
of landforms driven by rising sea
levels
•
Loss of exposures
Destruction of active and relict
landforms
Disruption of active processes
•
Loss of landform and outcrop
visibility
Physical damage to small scale
landforms
Stabilisation of dynamic landforms
(sand dunes)
Soil erosion and inversion/mixing
Changes to soil chemistry and soil
water regime
•
Landform damage through ploughing,
ground levelling and drainage
Loss of stabilising vegetation on
dunes and consequent erosion
Soil compaction, localised erosion,
loss of organic matter, reduction in
biodiversity
Effects of excess fertiliser
applications on soil chemistry and
biodiversity; changes to nutrient
status
Effects of pesticides on soil
biodiversity
•
Degradation of exposures and
landforms
Disruption of natural drainage
patterns (e.g. on saltmarshes)
Loss of topsoil and inversion/mixing
of horizons
changes to soil structure
Soil contamination
•
•
•
•
•
•
•
•
•
Changes to sediment
circulation and processes
downdrift
Increased erosion beyond
defences (flanking)
Reduction in sediment supply
downdrift and consequent
beach lowering
Changes to sediment
movement and processes
downstream
Change in process regime
Increase in sediment yield
and speed of run-off from
catchments during planting
and harvesting
changes to ground water and
surface-water chemistry
Changes in run-off response
times arising from drainage
Increased sand blow from
destabilised systems upwind
episodic soil erosion leading
to increased sedimentation
and chemical contamination
in lochs and river systems
Pollution of groundwater
Changes in run-off and
sediment supply
Drying out of wetlands
through local and distal
drainage
10 January, 2002
11. Recreation
(infrastructure,
footpath
development,
trampling, use of allterrain vehicles)
•
12. Soil pollution
•
•
Acidification of soils
Accumulation of heavy metals,
hydrocarbons and other PTEs
•
•
•
Deterioration of landforms
Loss of soils resource
•
•
•
Changes in active system processes
Changes in system state (reactivation
or fossilization)
With rising sea levels, increased
erosion and retreat of coastal
landforms
Risk of increased loss of soil carbon
13. Soil erosion
14. Climate change
•
•
•
•
•
Physical damage to small-scale
landforms and soils (compaction)
Loss of stabilising vegetation on
dunes and consequent erosion
Localized soil erosion
Loss of soil organic matter
•
•
•
•
•
15. Sea level rise
•
•
•
16. Fossil and
mineral collecting
•
•
Changes in coastal exposures and
landforms
Reduction in inter-tidal area of
landforms “coastal squeeze” where
landward transgression is prevented
by development or defences
With increased storminess,
increased erosion and retreat of
coastal landforms
•
Damage to and loss of
fossils/minerals
Deterioration and destruction of
fossil/mineral-bearing exposure
•
•
Downstream impacts on
watercourses
Contamination of
groundwater
Enhanced sedimentation
streams and lakes
Changes in water chemistry
Changes in flood frequency
Changes in sensitivity of
landforming environments
(rivers, coasts, etc.) leading
to changes in types and rates
of geomorphological
processes (e.g. erosion,
flooding)
Increased sand blow
landward of eroding
beach/dune systems
Changes in wider patterns of
erosion and deposition
enhanced flooding
Increased sand blow
landward of eroding
beach/dune systems
Loss to science
1
Impacts may be graded according to a simple scale of damage (e.g. 0–5).
2
Assessment of impacts depends on understanding of process links, thresholds for change and nature of feedback responses.
Page 80
10 January, 2002
10 References
Aldridge, R.J., Siveter, D.J., Siveter, D.J., Lane, P.D., Palmer, D. and Woodcock, N.H. (2000) British
Silurian Stratigraphy. Geological Conservation Review Series No. 19. Joint Nature Conservation
Committee, Peterborough.
Angus Council (1998) Montrose Bay Shoreline Management Study. Site B golf course frontage. Draft
Final Report to Angus Council by Sir William Halcrow and Partners Ltd.
Ballantyne, C.K. (1986) Landslides and slope failures in Scotland: a review. Scottish Geographical
Magazine, 102, 134–150
Ballantyne, C.K. (1997) The periglacial geomorphology of Scotland. In Gordon, J.E. (Ed.) Reflections on
the Ice Age in Scotland. An Update on Quaternary Studies. Scottish Association of Geography
Teachers and Scottish Natural Heritage, Glasgow, 166–178.
Ballantyne, C.K. and Harris, C. (1994) The Periglaciation of Great Britain. Cambridge University Press,
Cambridge.
Ballantyne, C.K. and Dawson, A.G. (1997) Geomorphology and landscape change. In Edwards, K.J.
and Ralston, I.B.M. (Eds) Scotland. Environment and Archaeology, 8000BC–AD1000. John Wiley,
Chichester, 23–44.
Brazier, V. and Ballantyne, C.K. (1989 Holocene debris cone evolution in Glen Feshie, western
Cairngorm Mountains. Transactions of the Royal Society of Edinburgh: Earth Sciences, 80, 17–24.
Brazier, V., Kirkbride, M. P. and Werritty, A. (1993) Scottish landform examples: the Clyde–Medwin
meanders. Scottish Geographical Magazine, 109, 45–49.
Brazier, V., Whittington, G. and Ballantyne, C.K. (1988) Late Holocene debris cone evolution in Glen
Etive, Western Grampian Highlands. Earth Surface Processes and Landforms, 13, 525–531.
Brunsden, D. and Prior, D.B. (Eds) (1984) Slope Instability. John Wiley, Chichester.
Cleal, C.J. and Thomas, B.A. (1995) Palaeozoic Palaeobotany of Great Britain. Geological Conservation
Review Series No. 9. Chapman and Hall, London.
Cleal, C.J. and Thomas, B.A. (1996) British Upper Carboniferous Stratigraphy. Geological Conservation
Review Series No. 11. Chapman and Hall, London.
Cleal, C.J., Thomas, B.A., Batten, D.J. and Collinson, M.E. (2001) Mesozoic and Tertiary Palaeobotany of
Great Britain. Geological Conservation Review Series No. 22. Joint Nature Conservation
Committee, Peterborough.
Clough, C.T., Maufe, H.B. and Bailey, E.B. (1909) The cauldron-subsidence of Glencoe and associated
igneous phenomena. Quarterly Journal of the Geological Society of London, 65, 611–676.
Comber, D.P.M., Hansom, J.D. and Fahy, F.M. (1994) Culbin Sands, Culbin Forest and Findhorn Bay
SSSI: documentation and management prescription. Scottish Natural Heritage Research, Survey
and Monitoring Report No. 14.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Curry, A. (2000) Holocene reworking of drift-mantled hillslopes in Glen Docherty, Northwest
Highlands, Scotland. The Holocene, 10, 509–518.
Davies, G.L. (1968) The Earth in Decay: A History of British Geomorphology 1578–1878. Macdonald
Technical and Scientific, London.
Dawson, A.G. (1999) Assessment of landform change in dune/machair systems of Coll and Tiree.
Unpublished report to Scottish Natural Heritage by the University of Coventry.
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. Geological Conservation Review
Series No. 16. Joint Nature Conservation Committee, Peterborough.
Ellis, N.V., Bowen, D.Q., Campbell, S., Knill, J.L., McKirdy, A.P., Prosser, C.D., Vincent, M.A. and
Wilson, R.C.L. (1996) An Introduction to the Geological Conservation Review. Joint Nature
Conservation Committee, Peterborough.
Emeleus, C.H. and Gyopari, M.C. (1992) British Tertiary Volcanic Province. Geological Conservation
Review Series No. 4. Chapman and Hall, London.
Gauld, J.H. and Bell, J.S. (1997) Soils and nature conservation in Scotland. Scottish Natural Heritage
Review, No. 62.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gemmell, S.L.G., Hansom, J.D. and Hoey, T.B. (2000) The geomorphology, conservation and
management of the River Spey and Spey Bay SSSIs, Moray. Scottish Natural Heritage Research,
Survey and Monitoring Report, No. 57.
Page 81
10 January, 2002
Gordon, J.E. (1997) Introduction: recent advances in Quaternary studies. In Gordon, J.E. (Ed.)
Reflections on the Ice Age. An Update on Quaternary Studies. Scottish Association of Geography
Teachers and Scottish Natural Heritage, Glasgow, 1–14.
Gordon, J.E. (in press)The Quaternary of Scotland. In Gerrard, A.J. and Fairbridge, R.W. (Eds)
Encyclopaedia of Quaternary Science. Kluwer, Dordrecht.
Gordon, J.E. and Campbell, S. (1992) Conservation of glacial deposits in Great Britain: a framework
for assessment and protection of Sites of Special Scientific Interest. Geomorphology, 6, 89–97.
Gordon, J.E. and Leys, K.F. (2001) Earth Science and the Natural Heritage: Interactions and Integrated
Management. The Stationery Office, Edinburgh.
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review
Series No. 6. Chapman and Hall, London.
Gregory, K.J. (1997) Fluvial Geomorphology of Great Britain. Geological Conservation Review Series,
No. 13. Chapman and Hall, London.
Hall, A.M. (1986) Deep weathering patterns in north-east Scotland and their geomorphological
significance. Zeitschrift für Geomorphologie, NF30, 407–422.
Hall, A.M. (1991) Pre-Quaternary landscape evolution in the Scottish Highlands. Transactions of the
Royal Society of Edinburgh: Earth Sciences, 82, 1–26.
Hansen M.J. (1984) Strategies for classification of landslides. In Brunsden, D. and Prior, D.B. (Eds)
Slope Instability. Wiley, Chichester, 2–23.
Hansom, J.D. and Black, D.L. (1996) The geomorphology of Morrich More: management prescription
review. Scottish Natural Heritage Research, Survey and Monitoring Report, No. 50.
Hansom, J.D. and Leafe, R.N. (1990) The geomorphology of Morrich More: development of a
scientific database and management prescription. Report for the Nature Conservancy Council,
Peterborough, by University of Sheffield.
Haynes, V.M. (1983) Scotland’s landforms: a review. In Clapperton, C.M. (Ed.) Scotland. A New Study.
David and Charles, Newton Abbot, 28–63.
Hinchliffe, S. (1999) Timing and significance of talus slope reworking, Trotternish, Skye, northwest
Scotland. The Holocene, 9, 483–494.
Innes, J. (1083) Lichenometric dating of debris flow deposits in the Scottish Highlands. Earth Surface
Processes and Landforms, 8, 579–588.
Leys, K. F. (1997) The Geomorphological Sensitivity of Selected Gravel-bed Rivers in Scotland. Unpublished
PhD thesis (2 Vols), University of Dundee
McEwen, L.J. (1986) River Channel Planform Change with Specific Reference to Climatic Fluctuation and
Landuse Changes over the Last 250 Years. Unpublished PhD thesis (2 Vols), University of St
Andrews.
McEwen, L.J. (1989) River channel change in response to flooding in the upper River Dee catchment,
Aberdeenshire, over the last 200 years. In Carling, P. and Bevan, K. (Eds) Floods: Hydrological,
Sedimentological and Geomorphological Implications. Wiley, Chichester, 219–238.
McIntyre, D.B. and McKirdy, A.P. (1997) James Hutton – The Founder of Modern Geology. The
Stationery Office, Edinburgh.
McManus, J. and Wal, A. (1996) Sediment accumulation mechanisms on the Tentsmuir coast. In
Whittington, G. (Ed.) Fragile Environments: The Use and Management of Tentsmuir National Nature
Reserve, Fife. Scottish Cultural Press, Edinburgh, 1–15.
Maizels, J.K. and Aitken, J. (1991) Palaeohydrological change during deglaciation in upland Britain: a
case study from northeast Scotland. In Starkel, L., Gregory, K.J. and Thornes, J.B. (Eds) Temperate
Palaeohydrology. Wiley, Chichester, 105–145.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Countryside
Commission for Scotland, Battleby, Perth.
May, V. and Hansom, J.D. Coastal Geomorphology of Great Britain. Geological Conservation Review
Series 24. Joint Nature Conservation Committee, Peterborough (in press).
Milne, R. and Brown T.A. (1997) Carbon in the vegetation and soils of Great Britain. Journal of
Environmental Management, 49, 413–433.
Mitchell, C. (1997) The geology of Scotland. In Gordon, J.E. (Ed.) Reflections on the Ice Age. An Update
on Quaternary Studies. Scottish Association of Geography Teachers and Scottish Natural Heritage,
Glasgow, 15–30.
Nature Conservancy Council (1976) Shetland. Localities of Geological and Geomorphological Importance.
NCC, Newbury.
Page 82
10 January, 2002
Nature Conservancy Council (1977) Outer Hebrides. Localities of Geological and Geomorphological
Importance. NCC, Newbury.
Nature Conservancy Council (1978) Orkney. Localities of Geological and Geomorphological Importance.
NCC, Newbury.
Peach, B.N., Horne, J., Gunn, W., Clough, C.T., Hinxman, L.W. and Teall, J.J.H. (1907) The Geological
Structure of the North-west Highlands of Scotland. Memoir of the Geological Survey of Great Britain.
Ritchie, W. and Mather, A.S. (1984) The Beaches of Scotland. Countryside Commission for Scotland,
Battleby, Perth.
Rowan, J.S., Black, S. and Schell, c. (1999) Floodplain evolution and sediment provenance
reconstructed from channel-fill sequences: the upper Clyde basin, Scotland. In Brown, A.G. and
Quine, T.A. (Eds) Fluvial Processes and Environmental Change. John Wiley, Chichester, 223–240.
Royal Commission on Environmental Pollution (1996) Sustainable Use of Soil. Nineteenth Report.
HMSO, London.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation
Committee, Peterborough.
SEPA (2001) State of the Environment. Soil Quality Report. Scottish Environmental Protection Agency,
Stirling.
Shennan, I., Innes, J.B., Long, A.J. and Zong, Y. (1995) Late Devensian and Holocene relative sea-level
changes in northwestern Scotland: new data to test existing models. Quaternary International, 26,
97–123.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Smith, D.E., Cullingford, R.A. and Firth, C.R. (2000) Patterns of isostatic uplift during the Holocene:
evidence from mainland Scotland. The Holocene, 10, 489–501.
Steel, M.E., Black, A.R., Werritty, A. and Littlewood, I.G. (1999) Reassessment of flood risk for
Scottish rivers using synthetic runoff data. In Hydrological Extremes: Understanding, Predicting,
Mitigating. Proceedings of IUGG ’99 Symposium HS1, Birmingham, July 1999, International
Association of Hydrological Sciences, IAHS Publication No. 255, 209–215.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J.
(1999) Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17.
Joint Nature Conservation Committee Peterborough.
Sutherland, D.G. (1984) The Quaternary deposits and landforms of Scotland and the neighbouring
shelves: a review. Quaternary Science Reviews, 3, 157–254.
Sutherland, D.G. and Gordon, J.E. (1993) The Quaternary in Scotland. In Gordon J.E. and Sutherland,
D.G. (Eds) Quaternary of Scotland. Chapman and Hall, London, 11–47.
Sutton, J. and Watson, J. (1951) The pre-Torridonian metamorphic history of the Loch Torridon and
Scourie areas in the North-west Highlands and its bearing on the chronological classification of
the Lewisian. Quarterly Journal of the Geological Society of London, 106, 241–307.
Taylor, A. (Ed.) (1995) Environmental Problems Associated with Soil in Britain. Scottish Natural Heritage
Review 55. Scottish Natural Heritage, Perth.
Taylor, A., Gordon J.E. and Usher M.B. (1996) Soils, Sustainability and the Natural Heritage. HMSO,
Edinburgh.
Wager, L.R. and Brown, G.M. (1968) Layered Igneous Rocks. Oliver and Boyd, Edinburgh.
Ward, S.D. and Evans, D.F. (1975) A botanical survey and conservation assessment of British
Limestone pavements. Volume IX. Collection and treatment of data. The limestone pavements of
Scotland. Unpublished report by ITE for NCC.
Werritty, A. and Brazier, V. (1991) The Geomorphology, Conservation and Management of the River
Feshie SSSI. Report for the Nature Conservancy Council, Peterborough, by the University of St
Andrews.
Werritty, A and Leys, K.F. (2001). The sensitivity of Scottish rivers and upland valley floors to recent
environmental change. Catena, 42, 251–274.
Whittington, G., Hall, A.M. and Jarvis, J. (1993) A pre-Late Devensian pollen site from Camp Fauld,
Buchan, Grampian Region, New Phytologist, 125, 867–874.
Wright, J.K. and Cox, B.M. (2001) British Upper Jurassic Stratigraphy. Geological Conservation Review
Series No. 21. Joint Nature Conservation Committee, Peterborough.
Page 83
10 January, 2002
Annex 1: The beaches of Scotland series
(prepared by Department of Geography, University of Aberdeen, for the Countryside
Commission for Scotland).
N
0
50
100
150
200km
10
9
1
3
2
8
6
14
4
5
Aberdeen
12
18
15
11
EDINBURGH
17
Glasgow
7
13
16b
16a
Figure A1.1 Location of regions covered by ‘The Beaches of Scotland Series (1969–1981)’
Map
no.
Report title: The Beaches of
Authors
Date
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16a
Sutherland
Caithness
Lewis and Harris
Barra and the Uists
West Inverness-shire and North Argyll
Wester Ross
Mainland Argyll
East Sutherland and Easter Ross
Orkney
Shetland
Islay, Jura and Colonsay
Northern Inner Hebrides
Cowal Bute and Arran
North East Scotland
Fife
South West Scotland Volume II (Solway
Firth)
South West Scotland Volume I (Firth of
Clyde)
Southeast Scotland
Tayside
Ritchie, W. and Mather, A.S.
Ritchie, W. and Mather, A.S.
Ritchie, W. and Mather, A.S.
Ritchie, W.
Mather, A.S. and Crofts, R.
Crofts, R. and Mather, A.S.
Crofts, R. and Ritchie, W.
Smith, J.S. and Mather, A.S.
Mather, A.S., Smith, J.S. and Ritchie, W.
Mather, A.S. and Smith, J.S.
Ritchie, W. and Crofts, R.
Mather, A.S., Smith, J.S. and Ritchie, W.
Ritchie, W.
Ritchie, W., Smith, J.S. and Rose, N.
Ritchie, W.
Mather, A.S.
1969
1970
1970
1971
1971
1971
1973
1973
1973
1974
1973
1974
1974
1978
1979
1979
Mather, A.S.
1979
Rose, N.
Wright, R.
1980
1981
16b
17
18
Page 84
10 January, 2002
Annex 2: The coastal cells of Scotland series
N
0
50
100
150
200km
Cape Wrath
Butt of
Lewis
Duncansby
Head
4
4
3
Cairnbulg
Point
9
8
5
3
Aberdeen
2
2
Barra
Head
1
5
Fife Ness
7
EDINBURGH
1
8
St Abb's
Head
Glasgow
6
Mull of
Kintyre
1
6
8
7
Mull of
Galloway
Coastal Cells
SMP areas
Solway
Firth
Figure A2.1 Shoreline Managements Plans (SMP) and shoreline assessments.
1 HR Wallingford (2000) Coastal Cells in Scotland. Cell 1 – St Abb’s Head to Fife Ness. Scottish Natural
Heritage Research, Survey and Monitoring Report, No. 143.
2 HR Wallingford (2000) Coastal Cells in Scotland. Cell 2 – Fife Ness to Cairnbulg Point. Scottish
Natural Heritage Research, Survey and Monitoring Report, No. 144.
3 HR Wallingford ( 2000) Coastal Cells in Scotland. Cell 3 – Cairnbulg Point to Duncansby Head.
Scottish Natural Heritage Research, Survey and Monitoring Report, No. 145.
4 HR Wallingford (2000) Coastal Cells in Scotland. Cell 4 – Duncansby Head to Cape Wrath. Scottish
Natural Heritage Research, Survey and Monitoring Report, No. 146.
5 HR Wallingford (2000) Coastal Cells in Scotland. Cell 5 – Cape Wrath to the Mull of Kintyre. Scottish
Natural Heritage Research, Survey and Monitoring Report, No. 147.
6 HR Wallingford (2000) Coastal Cells in Scotland. Cell 6 – Mull of Kintyre to the Mull of Galloway.
Scottish Natural Heritage Research, Survey and Monitoring Report, No. 148.
7 HR Wallingford (2000) Coastal Cells in Scotland. Cell 7 – Mull of Galloway to the Inner Solway Firth.
Scottish Natural Heritage Research, Survey and Monitoring Report, No. 149.
8/9
HR Wallingford (2000) Coastal Cells in Scotland. Cell 8 and 9 – The Western Isles. Scottish
Natural Heritage Research, Survey and Monitoring Report, No. 150.
10 HR Wallingford (2000) Coastal Cells in Scotland. Cell 10 – Orkney. Report to Scottish Natural
Heritage Research, Survey and Monitoring Report, No. 151.
11 HR Wallingford (2000) Coastal Cells in Scotland. Cell 11 -Shetland. Scottish Natural Heritage Research,
Survey and Monitoring Report, No. 152.
Page 85
10 January, 2002
Annex 3: Shoreline management plans
and shoreline assessments
1 Caledonian Geotech (1987) Tayside Regional Council, Coastal Erosion Study. Phase 2. Final Report.
Unpublished report to Tayside Regional Council. Dundee.
2 Halcrow Crouch (1998) Montrose Bay Shoreline Management Study. Unpublished report to Angus
Council and Glaxo Wellcome (2 volumes). November (1997) and January 1998.
3 Halcrow Crouch (1999) Aberdeen Bay Coastal Protection Study. Final Report. Unpublished report to
Aberdeen City Council, Scottish Natural Heritage and Grampian Enterprise. September 1999.
Aberdeen City Council, Aberdeen.
4 HR Wallingford (1995) Survey of Coastal Erosion in the Western Isles. Unpublished report to Scottish
Natural Heritage, the Western Isles Islands Council and the Minch Project. HR Wallingford Report
EX 3155. (1995)
5 HR Wallingford (1996) Shoreline Management Plan. Inverness Firth and part of Moray Firth (Burghead to
Sutors). Unpublished report to Highland Regional Council. HR Wallingford Report EX 3230.
September 1996.
6 HR Wallingford (1996) Saltcoats to Troon. Coastal Processes and Development. Unpublished report to
Scottish Natural Heritage and Strathclyde Regional Council. HR Wallingford Report EX 3327.
October 1996.
7 Posford Duvivier (1998) Shoreline Management Plan of Fife. Unpublished report to Fife Council (3
volumes). June 1998. Fife Council, Glenrothes.
8 Posford Duvivier (1998) St Abb’s Head to The Tyne Shoreline Management Plan. Unpublished report to
Wansbeck Council.
Page 86
10 January, 2002
PART 2
ZONAL DESCRIPTIONS
Figure 1
Page 88
Natural Heritage Zones in Scotland
10 January, 2002
ZONE 1
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
SHETLAND
Highlights
Lewisian-, Moine- and Dalradian-like lithologies that provide a link between the
Caledonides of mainland Scotland and northwest Europe.
The Unst Ophiolite, which provides an outstanding section through rocks of the oceanic
crust and upper mantle.
Occurrence of platinum group minerals and unusual mineralogy generally, associated
with the Unst Ophiolite.
Devonian stratigraphy, providing evidence of the north-western margin of the Orcadian
Basin.
A rich and diverse Devonian age fossil fauna and flora of international significance in
palaeoecological and evolutionary studies.
Influence of large- and small-scale faulting upon topography, habitat transition and the
development of voes.
The rare presence in Scotland of Quaternary interglacial and interstadial deposits, at
Fugla Ness and Sel Ayre.
Offshore and onshore evidence for the pattern of deglaciation of the last ice cap on
Shetland and adjacent shelves.
‘Drowned’ coastal landforms and archipelago landscape, with evidence for Holocene sea
level change in an area of limited uplift.
The presence of unique storm-generated, cliff top boulder beaches.
Spectacular rock coast landforms and processes, in particular on the exposed Atlantic
coasts, and including the second highest sea cliffs in Britain, on Foula.
The diversity and abundance of coastal spits, bars and tombolos, including St Ninian’s
Tombolo, the largest active sandy tombolo in Britain.
The development of active wind- and frost-related periglacial landforms at a relatively
low altitude in an exposed oceanic environment on Ronas Hill.
Detailed records of Holocene palaeoenvironmental change, human settlement and
human impacts on the landscape.
Deep peat and bog bursts.
Influence of geology upon soil type, particularly ultrabasic soils that support rare plant
communities.
Anthropogenic ‘plaggen’ soils.
Geology
The geology of Shetland is complex, principally as a result of a large number of major N–Sdirected faults, including the northward extension of the Great Glen Fault (the Walls
Boundary Fault), which has brought a large number of different rock types together in a
narrow zone. Shetland displays much of the geology of northern Scotland in miniature,
offering a traverse through the Lewisian, Moine and Dalradian rocks of the mainland in the
space of a few kilometres. Added to this, the superb section of oceanic crust and upper
mantle, the Unst Ophiolite, forming the eastern half of Unst and Feltar, makes Shetland an
area of extraordinary geological diversity.
The oldest rocks in Shetland are found along the Uyea–North Roe coastline on Mainland –
these range in age from 2900 to 1600 million years old, and are equivalent to the Lewisian
Complex of NW Scotland. The Lewisian Complex rocks are primarily acid rock types; these
Page 89
10 January, 2002
tend to be nutrient poor. These rocks form the basement on which the Moine and
Dalradian rocks were deposited, the latter forming the basis of the Caledonian Mountains
during subsequent continental collision.
Moine rocks dominate the geology of Yell and form part of northern Mainland. These largely
acid rocks, formed predominantly of metamorphosed sandstones, also tend to be nutrient
poor, which is one of the main factors giving rise to the blanket bog that covers these areas.
Much of central and eastern mainland, western Unst and Fetlar comprises Dalradian rocks.
The western portion of central Mainland consists of metamorphosed sandstones of the
Scatsta Division. The majority of this rock is nutrient poor, except for bands of
metamorphosed muds (pelites) that are rich in aluminium and iron. The central portion of
Mainland, west of the Nesting Fault, is dominated by the Whiteness Division. This sequence
contains a number of limestone formations, up to 500 m thick, which are exploited by a
number of valleys. The Clift Hills Division of eastern Mainland comprises metamorphosed
volcanic rocks. The contact between the Moine and Dalradian rocks is marked by the
spectacular Valayre Gneiss, which contains microcline crystals several centimetres in width.
The Walls Boundary Fault in Shetland is a continuation of the Great Glen Fault. It is a
complex structure with several offshoots. The Nesting Fault and its splays are short-cuts
across a major bend in the Walls Boundary Fault. The Bluemull Sound Fault, which runs up
the east side of Yell, is one of the splays off the Nesting Fault.
The Walls Boundary Fault has been the focus for movement between different crustal blocks
from the Devonian (400 million years ago) to the Jurassic (about 150 million years ago). Yell
has been shuffled along this fault zone to its current position between Mainland and Unst.
Most recently, the rocks on the east side of the Nesting and Bluemull Sound Faults have
moved to the north with respect to the rocks to the west.
During the final stages of closure of the Iapetus Ocean, a fragment of ocean crust was thrust
up onto the continental crust and this now forms the island of Fetlar and the eastern part of
Unst. Well exposed at Tressa Ness and Virva, this represents a remarkable slice through
oceanic crust and upper mantle. These ultrabasic and basic rocks give rise to a low, rolling
landscape with generally poor soils but with some rare plant communities. They have also
been a major source of chromite and talc, and more recently have been found to contain
Platinum Group Minerals, one of the few such areas in Britain.
Associated with the closure of the Iapetus Ocean was the generation of granitic intrusions.
To the east of the Walls Boundary Fault, the granites are older than the Devonian
sandstones and lavas; to the west, they are younger. Examples to the east of the fault
include the Brae, Graven and Spiggie Complexes; to the west there is the Sandsting and
Northmaven Complex, including Ronas Hill.
Devonian sandstones predominate on Bressay and south to the Sumburgh area, and they
also form the bulk of the Walls Peninsula, where they are well exposed at Fidlar Geo to
Watsness. Devonian age lava flows form part of the areas west of the Melby Fault, including
Esha Ness. The sedimentary sequences are important for understanding the geography and
environment of the north-western margin of the Orcadian basin and the ephemeral
freshwater lakes and rivers that persisted in this area during the Devonian period.
Page 90
10 January, 2002
3
Palaeontology
The fossil heritage of Shetland occurs within the Devonian sequences that were laid down
on the north-western margin of the Orcadian Basin, a vast inland lacustrine–fluvial
environment. Primitive armoured fish, the lungfish forerunners of amphibians and reptiles,
and the ancestors of today’s bony fish, are all represented. Fossil fish are found
predominantly in fine-grained laminated sediments deposited in the deepest parts of the lake
environment. The most famous ‘fish beds’ are those at Melby, which represent the
northernmost extension of the Achanarras Fish Bed of Caithness. Other nationally
important fish beds occur at The Cletts, Exnaboe and at Sumburgh Head. Associated with
the fossil fish remains are the remains of fossil plants washed into the ancient Devonian lake
from the surrounding landscape. The fossil beds at Bu Ness, on Fair Isle, yield an
internationally significant fossil flora that is important in evolutionary studies of
progymnosperms. Detailed analysis of the Devonian sedimentary sequences, and the fossil
fish and plants, have allowed the construction of ecological models of the ancient basin
environment.
4
Geomorphology
Topographically, the most striking feature of Shetland is its north–south elongation and the
presence in the eastern half of the island group of smooth N- to NE-trending ridges with
intervening partly drowned valleys. Here, the underlying geology comprises schists (quartzfeldspar- and mica-rich rocks) in which the minerals are aligned to produce a fabric that
trends N or NE. In general, the weaker rocks have been eroded to produce the pattern of
linear hills and ridges. More gentle country in the east is underlain by sandstones of
Devonian age. The western part of the island group is separated geologically by the Walls
Boundary Fault. In the west, the topography is more diverse and rugged than in the east,
reflecting the varied bedrock geology of the area, including several masses of granite, belts
of schist, some highly folded sandstones, and andesite and basalt lavas.
Glacial erosion, strongly guided by underlying rock structures, has emphasised the main
landscape elements. In general, Shetland bears a stronger imprint of glacial erosion than
Orkney, reflected in the frequency of occurrence of glaciated valleys and fjords. Much of the
inland area of Shetland is dominated by ice-scoured rocky hills and with peat over a
generally thin drift cover. During the last glaciation, the islands were at the centre of a local
ice cap, and most of the drift was deposited on the shelf offshore. Hence there is a paucity
of unconsolidated material for soil development.
Shetland occupies a critical location on the margins of NW Europe at the junction of major
oceanic areas: the North Sea, the Norwegian Sea and the Atlantic Ocean. The region is
climatically sensitive because of its proximity to the atmospheric and marine polar fronts
and the moderating influence of the North Atlantic Drift. The landforms and deposits of the
islands and the adjacent shelves therefore hold potentially valuable records for
reconstructions of palaeoclimate and glacier dynamics, in particular through the opportunity
to link onshore and offshore records of glacier response to both climate and sea level
forcing to provide an integrated picture of deglaciation of the last ice sheet which extended
out across the continental shelf. Shetland is also a key area for studies of glacial history
because of the rare preservation of pre-last ice sheet deposits at two sites, Fugla Ness and
Sel Ayre. In general, other glacial and glaciofluvial landforms are rare. Moraines occur locally,
for example on Papa Stour and at Burn of Mail; meltwater channels occur in northern Unst,
Page 91
10 January, 2002
and at Dalsetter there is an erratic boulder believed to have been transported from
Scandinavia. Raised shorelines are absent and the coastline is essentially one of
submergence. Relative sea level was at least 9 m lower than present around 5500 BP and
submerged peat beds are common. Records of later sea level changes have been obtained
from coastal sites on Unst. A possible middle Holocene tsunami/flood deposit has also been
discovered at Garths Voe on the Mainland.
Climate and exposure also determine soil instabilities on the hills. Ronas Hill is particularly
noted for its assemblage of active and fossil periglacial landforms (including a variety of frostand wind-related patterned ground and solifluction features normally found at much higher
altitudes on the Scottish mainland) developed at a relatively low altitude under the extreme
subarctic oceanic climate of the area, characterised by wet and windy conditions. The
presence of buried soils may allow the establishment of episodes of vegetation
destabilisation and possible links with changes in climate or grazing. Elsewhere, small, active
stone stripes are present on the serpentine soils of Keen of Hamar, where vegetation
development is retarded.
The ice-scoured landscape includes areas of closed basins and impeded drainage. Thus
climate and geology have favoured the growth of peat, which covers large parts of central
and western Mainland, western Unst and Yell. Peat is less common on the serpentine and
greenstone areas of Unst and Fetlar and on the igneous rocks of North Roe. Peat erosion
occurs extensively, e.g. on the Cunningsburgh hills and on Yell. Spectacular examples of bog
bursts occurred in Delting, north of Voe, in 1992. Peat mounds are well developed on the
north side of Ronas Hill (in the this case probably the result of topography rather than the
rocks themselves preventing peat formation). Palaeoenvironmental records from peatbogs
and loch sediments show evidence of former woodland, and during the early–middle
Holocene there was a phase when trees, particularly birch and hazel, were widely
developed. Willow, oak and alder were also present. Significant woodland contraction
occurred through human activity after 5000 14C yr BP, and particularly around 3000 14C yr
BP, and peatland cover expanded.
Shetland’s coastline is a mixture of exceptionally exposed, often cliffed, rocky shores
containing small pocket beaches of shingle and occasionally sand, and more sheltered
shorelines with thin fringing beaches of angular pebbles worked out from the local till
deposits. Sandy beaches are relatively uncommon compared with the rest of the country,
possibly because of the steepness of the near-shore shelf, although there exist a few notable
exceptions such as Quendale Bay and Balta Island, where a machair-like landform and
habitat has developed across much of the island.
The coastline is so convoluted that no part of Shetland is more than 5 km from the coast.
Much of this coastline is characterised by drowned glacial valleys, known locally knows as
voes. These long sea lochs and the many islands provide, locally, very sheltered conditions
where, for example, saltmarsh can develop, as at Dales Voe on North Mainland. However,
the islands’ latitude, steeply sloping nearshore shelf and unobstructed fetches to the Atlantic
make many of its outer shorelines among the most exposed in the UK. Spectacular cliffed
coastlines result, displaying the full range of cliff-related landforms, such as at Foula, the
Villians of Hamnavoe and Papa Stour. At 370 m, the Kame in Foula is the second highest sea
cliff in the UK. The exceptional exposure endured by this island has, in addition, led to the
formation of unique storm-generated boulder beds, containing blocks in excess of 1 m
diameter, resting up to 35 m above sea level.
Page 92
10 January, 2002
General submergence in the Holocene of the formerly glaciated landscape has led to the
formation of numerous sand and, especially, shingle bars, tombolos and spits, known locally
as ayres, at or across the heads of many sea lochs and bays and occasionally between
separate islands. (Ayre simply means beach and is applied to ordinary beaches as well as to
bars and tombolos; an oyce is a loch behind a shingle bar; houb is a generic term for a
lagoon.) The abundance and diversity in form of these features is unparalleled elsewhere in
the UK and is exemplified by St Ninian’s tombolo, the largest active sandy tombolo in
Britain, and the Ayres of Swinister, a unique triple tombolo linking the island of Fora Ness
with North Mainland.
There are no major rivers on Shetland, which is partly a reflection of the small catchments,
and Shetland’s fluvial resources have not been the subject of detailed research. There are,
however, a significant number of short burns and small lochans, particularly on Unst, Yell
and parts of Mainland. Few of the streams and burns have particularly gravelly beds, and
many are incised into peat or directly into bedrock. The relatively small size of some islands
and the resistant bedrock, coupled with the local altitudes and gradients, do not provide the
opportunity for the downstream development of channel form. Many burns (particularly
those on north and west Yell) drain to the sea via coastal waterfalls, demonstrating that the
rate of coastal retreat exceeds that of burn incision. On the more sheltered sides of the
islands, a number of streams have become incised into the underlying material and drain
gradually to the sea forming small estuaries. The most complicated stream networks can be
found on the Mainland, with third-order streams at Starkigarth (HU 4329) and Voe, and the
large area occupied by surface water, mires and bogs is a reflection of the climate and
underlying geology. There are no fluvial geomorphology GCR sites on Shetland, but this may
be a function of the paucity of research rather than a reflection on the value of the
resource.
5
Soils
Most of Shetland is dominated by deep peat as a result of the nature of the underlying rock
and drift, poor drainage, climatic conditions and woodland clearance. Associated with the
peat are moorland plant communities. There are also large areas of peaty gleys and peaty
podzols, so that the soils on Shetland contain substantial soil carbon reserves. Cultivated
land is found on the coastal fringes on shelly windblown sands, or on crystalline limestones –
both giving calcium-rich soils (brown calcareous soils) and on drift-derived soils. The unique
Lesley Association is developed on the serpentinite rocks of Unst and Fetlar – these
magnesium-, nickel- and chromium-rich rocks give rise to magnesian gleys and brown
magnesian soils, which are base-rich soils that sustain rare plant communities but can give
nickel toxicity problems. Soils formed from ultrabasic parent materials or calcareous
substrates are particularly valuable as they are the most capable of supporting arable
agriculture and can also sustain semi-natural vegetation tolerant of high nickel
concentrations. Some soils such as those on Papa Stour have been altered by human activity
over many years to improve fertility through application of calcareous materials and organic
matter. These ‘plaggen’ soils (see also Zone 2) are of national significance along with saline
gleys found on some exposed coasts. In summary, the peat soils on Shetland contain very
large reserves of soil carbon which are prone to instability and erosion. The more unique
soils are those which are also most agriculturally productive as they are formed on basic
parent materials; in their natural state these areas support unique plant communities and
habitats.
Page 93
10 January, 2002
6
Summary of key Earth science features in Shetland
The principal Earth heritage interests in Shetland are summarised in Table 1.1. Shetland
includes a total of 43 GCR sites.
Table 1.1
GCR sites in Shetland
GCR block
No. of sites
Principal interests
Moine
6
Caledonian Structures
2
Ordovician Igneous
6
Non-marine Devonian
3
ORS Igneous
2
Mineralogy
Palaeobotany
8
1
Vertebrate Palaeontology
Quaternary of Scotland
4
5
Coastal Geomorphology
6
Representative sites for understanding the
origin and development of the Moine
Geological structures that elucidate the
Caledonian Earth movements
Igneous rocks associated with the Unst
Ophiolite
Representative sites for Devonian
sedimentology
Representative sites for igneous activity that
took place during the Devonian
Unusual and rare minerals
Fossil remains of primitive Devonian
landplants
Rich and diverse freshwater fossil fauna
Quaternary stratigraphy, Lateglacial and
Holocene vegetation history and periglacial
geomorphology
Beach/machair, bar/tombolo landforms and
rock geomorphology
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in Shetland are summarised in Table 1.2. However, there is no systematic
information on current impacts or trends.
Page 94
10 January, 2002
Table 1.2
Potential pressures and vulnerability of Earth heritage interests in Shetland
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction and infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure
developments; land management changes; construction
of tracks; afforestation; river management
Vulnerable to mineral extraction/quarrying; commercial
and industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Generally robust to all but large scale developments such
as superquarries
Vulnerable to mineral extraction from beaches; coast
protection; commercial and industrial developments land
claim and sea level rise
Vulnerable to land management changes, pollution, peat
erosion
Vulnerable to enhanced erosion through overgrazing and
increased recreational pressures
Vulnerable to drainage of bogs and peat extraction
Palaeontological interests
Mineralogical interests
Quaternary depositional landforms
and exposures
Records of sea level change
Rock coast features
Coastal spits and bars
Soils
Periglacial geomorphology
Palaeoenvironmental records
8
•
•
•
•
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
The condition of all coastal GCR sites in south and east Mainland, following the oil spill
from the Braer tanker in January 1993, was assessed in February of that year. The results
are published in SNH RSM Report No 12.
The ‘fish beds’ at Melby and The Cletts, Exnaboe, show evidence of having been
‘quarried’ on a minor scale for fossils.
Peat erosion is considered to be significant.
Sea level rise may have a greater impact in Shetland than in more central parts of
Scotland.
There is a possible threat to Fugla Ness Quaternary deposits from a proposed tidal
power generation scheme.
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Region 1. Shetland. Joint Nature Conservation Committee, Peterborough.
Bennett, K.D., Boreham, S., Sharp, M.J. and Switsur, V.R. (1992) Holocene history of environment,
vegetation and human settlement on Catta Ness, Lunnasting, Shetland. Journal of Ecology, 80, 241–273.
Bennett, K.D., Bunting, M.J. and Fossitt, J.A. (1997) Long-term vegetation change in the Western and
Northern Isles, Scotland. Botanical Journal of Scotland, 49, 127–140.
Birnie, J.F., Gordon, J.E., Bennett, K.D. and Hall, A.M. (1993) The Quaternary of Shetland. Field Guide.
Quaternary Research Association, Cambridge.
Page 95
10 January, 2002
Cleal, C.J. and Thomas, B.A. (1995) Palaeozoic Palaeobotany of Great Britain. Geological Conservation
Review Series No. 9. Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. GCR Series No. 16. Joint Nature
Conservation Committee, Peterborough.
Flinn, D. (1994) Geology of Yell and some neighbouring islands in Shetland. Memoirs of the British
Geological Survey. HMSO, London.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Goodier, R. (Ed.) (1974) The Natural Environment of Shetland. Nature Conservancy Council, Edinburgh.
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
HR Wallingford (2000) Coastal Cells in Scotland. Cell 11 – Shetland. Report to Scottish Natural Heritage,
Scottish Office (Agriculture, Environment and Fisheries Department) and Historic Scotland. Scottish
Natural Heritage Research, Survey and Monitoring Report, No. 152.
Lees, G. (1994) Effects of the Braer Oil Spill on Sites of Special Scientific Interest in the Shetland Islands.
Scottish Natural Heritage Research, Survey and Monitoring Report, No. 12.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Department of
Geography, University of Aberdeen. Countryside Commission for Scotland, Perth.
Mather, A.S. and Smith, J.S. (1974) Beaches of Shetland. Department of Geography, University of
Aberdeen. Countryside Commission for Scotland, Perth.
May, V. and Hansom, J.D. (in press) Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Mykura, W. (1976) British Regional Geology: Orkney and Shetland. British Geological Survey. HMSO,
Edinburgh.
Nature Conservancy Council (1976) Shetland. Localities of Geological and Geomorphological Importance.
NCC, Newbury.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Stoker, M.S., Hitchen, K. and Graham, C.C. (1993) United Kingdom Offshore Regional Report: the Geology of
the Hebrides and West Shetland Shelves, and Adjacent Deep-water Areas. British Geological Survey,
HMSO, London.
Whittington, G. and Edwards, K.J. (1993) Vegetation change on Papa Stour, Shetland: a response to
coastal evolution and human interference? The Holocene 3, 54–62.
10
Maps
British Geological Survey Maps: 1:50,000 Shetland ‘Special Sheets’.
Soil Survey of Scotland Maps 1:250,000 sheet 1 and uncoloured 1:50,000 sheets 1, 2, 3 and 4. MLURI,
Aberdeen.
Page 96
10 January, 2002
ZONE 2
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
NORTH CAITHNESS AND ORKNEY
Highlights
A sedimentary rock sequence that spans the Lower, Middle and Upper Devonian,
encompassing both central and marginal areas of the Devonian Orcadian Basin, and
providing an outstanding insight into Devonian terrestrial palaeoecology and
palaeoenvironments.
The only Middle Devonian sedimentary rocks in Scotland.
Several fossil-fish-type localities and the location of the world famous Achanarras Fish
Bed.
A rich and diverse Devonian age fossil fauna and flora of international significance in
evolutionary studies.
Fossil evidence of the world’s oldest primitive progymnosperm.
The best stromatolite beds in the Orcadian Basin.
Glacial landforms on Hoy.
Rare occurrence of pre-last glaciation raised beach deposits on Hoy.
Glacial deposits that provide evidence for the pattern and timing of last ice-sheet
glaciation on Orkney and adjacent shelves.
‘Drowned’ coastal landforms and archipelago landscape, with evidence for Holocene sea
level change in an area near the periphery of isostatic uplift.
Exceptional diversity and expression of cliff-related landforms, including the third highest
sea-cliffs in Britain, at St John’s Head, Hoy, and the renowned Old Man of Hoy sea stack.
Beach/dune landforms and processes, including the rare occurrence of machair and
aeolianite outside of NW Scotland.
Rapid and continuing beach and dune formation against Churchill Barrier No. 4.
Active periglacial landforms and processes in low-altitude maritime environment.
Detailed records of Holocene palaeoenvironmental change, human settlement and
human impacts on the landscape.
Anthropogenic soils surrounding old settlements.
Geology
The Orkney Islands, with the exception of Hoy, generally have a more subdued topography
than Shetland. Most of the islands are formed from sedimentary rocks of Devonian age –
local variations in the hardness of the rock sequence give rise to variations in the local
topography, including some striking features, such as the cliffs on the west coast of Hoy.
The zone comprises various aspects of the Lower, Middle and Upper Devonian geology. It is
significant that Middle Devonian rocks do not occur anywhere else in Scotland.
Lower Devonian sedimentary rocks are restricted to the western part of Caithness, where
they sit against the northern part of the Strath Halladale granite and on top of the Moine
basement. At Red Point Coast there is the occurrence of a ‘fossil’ beach environment where
Middle Devonian rocks, comprising rippled sands, beach gravels and scree, lie
unconformably upon the old basement rocks. Eastwards and northwards from Red Point,
Middle Devonian sedimentary sequences dominate the geology of Caithness and Orkney,
with Upper Devonian rocks forming Dunnet Head and most of Hoy.
The Devonian sedimentary rocks of Caithness and Orkney were deposited in the Orcadian
basin, a large inland depression that drained the Highlands to the west and south.
Page 97
10 January, 2002
Throughout the Devonian, the basin received vast quantities of sand silt and mud, which
accumulated to a depth of several kilometres. For considerable intervals of time, the arid
desert conditions, evidenced by sand dune deposits at Yesnaby and elsewhere, gave way to
the development of ephemeral lakes. During a large portion of the Middle Devonian, the
lakes merged to form one vast inland freshwater lake, termed the Orcadian Basin Lake or
Lake Orcadie, which extended from the Moray Firth across zone 2 to Shetland and Norway.
The basin lake was home to a very rich and diverse fish fauna that lived and died in the
surface and marginal waters. The rivers emptying into the lake(s) also contained fish, some
of which migrated into the area from a sea that lay to the south-east in what is now the
southern North Sea. Around the lake and on the extensive river plains, primitive plant life
would have thrived. The fossil remains of this ancient fauna and flora are to be found
beautifully preserved within the lake sediments.
The largely quiescent conditions of deposition and extensive nature of the Orcadian basin
have given rise to the remarkably consistent beds of the Middle Devonian of Caithness and
parts of Orkney. These form the basis of the flagstone industry in this area, with quarrying
currently occurring at Spittal for example.
3
Palaeontology
The Orcadian Basin Lake sediments contain numerous ‘fish beds’, of which the Achanarras
Fish Bed, exposed at Achanarras, is one of the most important Devonian fossil fish sites in
the world. The Achanarras Fish Bed and other fish beds in the zone, for example at
Banniskirk in Caithness and the Sandwick Fish Bed at Cruady Quarry on the West Mainland
of Orkney, have yielded the remains of a rich and diverse fish fauna that lived and died
within the Devonian lacustrine–fluvial environment. Primitive armoured fish, the lungfish
forerunners of amphibians and reptiles, and the ancestors of today’s bony fish, are all
represented. The Achanarras Fish Bed has yielded over 14 genera and is the type locality for
two species; it is therefore of international significance. Population studies of this and other
fish beds have suggested that some of the fish species lived entirely within the ancient basin
environment, whereas others migrated from a southern ocean via an ancient river system.
Fish remains found in fluvial portions of the sequence provide evidence of widespread niche
utilisation and migratory habits.
Deposits of fossil plant material found in association with the fish faunas, at Bay of Skaill for
example, provide important palaeobotanical evidence of the basin flora surrounding the
Devonian lakes and rivers. In addition to its palaeoecological importance, the Bay of Skaill
locality is of international significance for being the type locality for the earliest known
progymnosperm.
The zone also yields the best algal stromatolite beds in the Orcadian Basin, at Yesnaby on
the West Mainland of Orkney. These ‘fossil’ beds, in part biogenically produced, are an
important palaeoenvironmental and palaeogeographic indicator.
4
Geomorphology
Glacial erosion is believed to have deepened some of the firths between the Orkney Islands,
but only north Hoy has prominent glacial erosional features such as glacial troughs and
Page 98
10 January, 2002
corries. Elsewhere, harder bands of sandstone have been picked out by glacial erosion,
giving rise to escarpments and terraced slopes, as on Rousay. Otherwise, glacial erosion on
Orkney and in Caithness appears to have been relatively limited, confined to moulding and
smoothing the landscape. In Caithness, there is a strong SE–NW grain to the ice moulding,
reflecting the former ice movement direction. The drift cover in both Orkney and Caithness
is more widespread and thicker than in Shetland and is exposed in many coastal sections.
The till cover, particularly in the eastern parts, includes erratic material (with shells) derived
from offshore and transported towards the northwest by the ice (as at Mill Bay on
Stronsay); erratics of Scandinavian origin have also been identified, notably the Saville
boulder on Sanday. These deposits are of significant interest for interpreting the former
pattern of movements of the last ice sheet from the Moray Firth to the Atlantic. Elsewhere
in Caithness, substantial thickness of till infill pre-existing depressions and valleys. Like
Shetland, the occurrence of clear moraines and glaciofluvial landforms is generally
uncommon in this zone. Hummocky drift occurs locally on Mainland Orkney, notably near
Finstown, and on Rousay. North Hoy, however, is exceptional for a superb assemblage
glacial deposits. These include corrie moraines at Enegars Corrie and Dwarfie Hamars and a
huge glaciofluvial terrace in the valley leading to Rackwick. These landforms have not been
studied in detail but could potentially provide critical evidence for the pattern and timing of
ice-sheet wastage and Late-glacial events. If the corrie moraines relate to the Loch Lomond
Stadial, then they were among the lowest in Scotland at that time. The Caithness tills appear
relatively weathered and have been significantly modified by solifluction. This has led to
claims that both they and the tills of Orkney pre-date the Late Devensian glaciation, but this
now appears unlikely from what is known about the offshore extent of the last ice sheet.
On north Hoy there are two rare exposures of raised beaches that pre-date the last
glaciation of the islands. Postglacial raised beaches, however, are absent from Orkney, and
like Shetland the coastline is essentially one of submergence. Records of coastal changes
have been obtained from sites at Scapa Bay and Bay of Skaill. In Caithness, a detailed record
of Holocene sea level changes has been obtained from the lower valley of the Wick River.
This shows that two later higher transgressions followed the Main Postglacial Transgression.
The middle Holocene tsunami deposit that occurs widely in eastern Scotland is also
represented. Such areas near the periphery of isostatic uplift are of particular interest for
establishing sea level fluctuations, since the signal is less likely to be complicated by isostatic
effects.
The higher hills of Hoy (Ward Hill, Cuilags) are particularly exposed and display a range of
periglacial features related to frost, wind and solifluction processes. Like those of Ronas Hill
on Shetland, these are exceptional on a national scale for their degree of development at a
relatively low altitude and reflect the extreme subarctic oceanic climate of the area. The
wind-related features on Ward Hill are particularly well developed. The presence of buried
soils may allow the establishment of episodes of vegetation destabilisation and possible links
with changes in climate or grazing.
Palaeoenvironmental records from peatbogs on Orkney show evidence of former
woodland, and during the early–middle Holocene there was a phase when trees, particularly
birch, hazel and willow, were widely developed; oak, alder and pine were also present.
Significant woodland contraction occurred through human activity after 5000 14C yr BP, and
peatland cover expanded. In Caithness, pollen studies from Loch of Winless and other sites
suggest that the north-east part of the area and the Flow Country to the south and west
were never extensively forested during the Holocene. In the north-east, birch, willow and
Page 99
10 January, 2002
hazel scrub were probably present in sheltered areas, possibly with some elm and alder. In
the south-west, pine expanded briefly about 4000 14C yr BP before contracting, probably in
response to climatic deterioration, although other stresses might have contributed.
Woodland clearance through human activity probably began around 3000 14C yr BP.
The coastline of this zone is characterised by cliffs cut into the Old Red Sandstone strata
and by sandy bays fronting well developed beach–dune–machair complexes. These dominant
coastal forms are interspersed with frequent pocket beaches of shingle and cobbles and,
locally, sand and shingle spits.
Like Shetland and the west coast of the Western Isles, Orkney’s coastline is exceptionally
exposed as a result of its latitude and unobstructed fetches of hundreds or thousands of
kilometres to the east and west, although, unlike Shetland, some attenuation of wave energy
is afforded by the relatively shallow offshore gradient.
Cliffs are, likewise, very well developed both on Orkney and on the adjacent mainland, the
most spectacular examples being the renowned sea stacks at Duncansby Head and the Old
Man of Hoy. The third highest sea cliffs in the UK (335 m) occur at St John’s Head on the
Island of Hoy. These cliffs all occur in Old Red Sandstone but display wide variations in form
because of differences in bedding structure and lithology. In particular, the highly jointed and
fissile nature of these sandstones has, with the high wave energy, led to the creation of an
exceptionally wide range of distinctive cliff landforms such as stacks or ‘castles’, arches,
caves, geos (deep clefts in the cliff), blowholes and wave-cut notches. The diversity and
exceptional preservation of these is perhaps greater than anywhere else in the UK.
Sandy beaches are common and well developed in this zone, especially relative to Shetland.
Extensive dune systems occur at Dunnet Bay in Caithness and on the Island of Sanday. The
exposed location and calcareous nature of some of these beach sands make many of the
associated links areas very similar to the machairs of the west coast (e.g. the Plain of Fidge
on the Island of Sanday). Aeolianite, a rare landform associated with machair, is particularly
well-preserved on Orkney, for instance at Evie and Warbeth on the Mainland.
Evidence of the dynamic shifting nature of the Scottish coastline is demonstrated especially
clearly at two sites in Orkney: the Bay of Skaill (Mainland), where the Neolithic village of
Skara Brae has been successively inundated and then cleared of sand, and the Churchill
Barrier No. 4, a causeway linking South Ronaldsay and Burray which, since its construction
in 1944, has caused the accumulation of a 50m broad beach and dune system on its eastern
flank.
There are very few large rivers on the Orkney Islands, although there are a number of third
order streams on the Mainland, including Burn of Woodwick and Burn of Hillside. The
Mainland also supports the largest of the lochs seen in Orkney, with both Loch of Stennes
and Loch of Harray being several square kilometres in size. Outwith the Mainland, the
majority of the islands support small burns and lochans, some of which are extremely small
(e.g. Mor Stein on Shapinsay). In many of the small northern islands (Papa Westray, North
Ronaldsay, Westray, Sanday, Eday and Rousay), the surface water is mainly standing water in
the form of lochs and lochans with little running water apparent. In Rousay, many of those
small burns enter the sea via coastal waterfalls. The drainage patterns of the Mainland and
Hoy differ from that of the northern islands, with a more dense stream network apparent.
Hoy drains east and west from a central watershed and has a number of small lochans. The
Page 100
10 January, 2002
difference in the drainage patterns is likely to be a function of the different geology. No
detailed research has been carried out into the fluvial geomorphology of the Orkney Islands,
so little information is available about the quality of the resource.
The drainage basins of the rivers in North Caithness are significantly larger than those in the
Orkney Islands. The zone is lowland and relatively flat, so that the larger north-flowing
rivers (the lower reaches of the River Thurso and the Forss Water) have sinuous
meandering planforms. The north-flowing rivers appear to have developed at the expense of
those flowing into the Moray Firth through the process of headwater capture. The River
Thurso, which has a fine-grained gravel bed in its lower course, has a relatively wide
meander train and irregular rectangular meanders. The course of the River Thurso reflects
rock and glacial drift influences, and it dissects a moraine only 2 km from Thurso. The Forss
Water also has a sinuous lower reach with an irregularly meandering upper section which is
situated within Zone 5. The north–south aligned reaches are in conformity with the strike
of the rocks, whereas the east- to west-flowing sections conform with the regional slope.
The Gill Burn, which drains east, has a relatively large catchment area and a number of firstto third-order tributaries. Despite this, the channel is still relatively narrow when it reaches
the sea. The Burn of Lyth has a similarly large catchment and, unusually, a loch in the lowermiddle reaches. The River Wick follows an interesting course, with some headwater
tributaries initially flowing north before meeting Loch Watten and flowing east into the sea.
The River Wick is generally within an area of gentle topography and there are meanders in
both the headwaters of the tributaries and the middle reaches of the Wick itself before it
becomes sinuous in the lower reaches.
5
Soils
On Orkney deep peat is confined to central and southern Hoy and the hills of eastern and
southern Mainland. The majority of soils in this zone are peaty gleys, reflecting the presence
of excess moisture and poor drainage. Saline gleys occur along the coastline of many of the
islands, where soils have been influenced by saline water. Sanday has substantial numbers of
calcareous gleys and brown soils, developed where shelly deposits have given rise to
calcareous soils. These calcareous soils support diverse plant communities and are
potentially the most agriculturally productive soils. Caithness also has pockets of calcareous
gleys and calcareous brown soils on the coast. Small-scale erosion of soils is largely confined
to peat deposits where changes in land use have triggered this. In some sites close to old
settlements soils have been modified by human activity through the addition of calcareous
materials and organic matter to produce unique anthropogenic soils with deep topsoils.
Soils of local significance include those modified by human activity around old settlement
sites and Regosols at Dunnet Links, where Primula scotica is found. Peat deposits are prone
to instability and erosion especially where drainage associated with afforestation has
occurred.
6
Summary of key Earth science features in North Caithness
and Orkney
The principal Earth heritage interests in North Caithness and Orkney are summarised in
Table 2.1. North Caithness and Orkney includes a total of 28 GCR sites.
Page 101
10 January, 2002
Table 2.1
GCR sites in North Caithness and Orkney
GCR block
No. of sites
Principal interests
Non-Marine Devonian
8
Old Red Sandstone Igneous
2
Vertebrate Palaeontology
Palaeozoic Palaeobotany
Quaternary of Scotland
9
1
4
Coastal Geomorphology
2
Representative sites for Devonian
palaeoenvironment
and palaeoecological studies
Representative sites for igneous activity that took
place during the Devonian
Rich and diverse freshwater fauna
Middle Devonian progymnosperms
Representative sites for last ice-sheet deposits and
flow patterns, periglacial geomorphology and
Holocene vegetation history; rare pre-last ice sheet
raised beach deposits
Beach and machair; rock coast landforms and
processes
7
Pressures and trends
The potential pressures on different components of the Earth heritage in North Caithness
and Orkney, and their vulnerability, are summarised in Table 2.2. However, there is no
systematic information on current impacts or trends.
Table 2.2
Potential pressures and vulnerability of Earth heritage interests in the North Caithness
and Orkney
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction and infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; coast protection
Vulnerable to enhanced erosion through overgrazing and
increased recreational pressures
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Generally robust to all but large scale developments such as
superquarries
Vulnerable to sand and gravel quarrying, coast protection,
sea level change
Vulnerable to river engineering and management;
afforestation gravel extraction; land management changes
Vulnerable to drainage of bogs and peat extraction
Vulnerable to land management changes, pollution
Palaeontological interests
Quaternary depositional landforms
and exposures
Periglacial geomorphology
Records of sea level change
Rock coast features
Beach and machair systems
Fluvial geomorphology
Palaeoenvironmental records
Soils
Page 102
10 January, 2002
8
•
•
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Cruady Quarry shows evidence of irresponsible fossil collecting, with rock saws having
been used to remove fossils.
Peat erosion is significant in parts of Hoy and Caithness; further erosion would be a
significant threat to peat deposits/soils across the area.
Sea level rise may have a greater impact in North Caithness and Orkney than in more
central parts of Scotland.
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Region 2. Orkney. Joint Nature Conservation Committee, Peterborough.
Bennett, K.D., Bunting, M.J. and Fossitt, J.A. (1997) Long-term vegetation change in the Western and
Northern Isles, Scotland. Botanical Journal of Scotland, 49, 127–140.
Bunting, M.J. (1994) Vegetation history of Orkney, Scotland; pollen records from two small basins in
west Mainland. New Phytologist, 128, 771–792.
Cleal, C.J. and Thomas, B.A. (1995) Palaeozoic Palaeobotany of Great Britain. Geological Conservation
Review Series No. 9. Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Davidson, D.A. and Simpson, I.A. (1984) Deep topsoil formation in Orkney. Earth Surface Processes and
Landforms, 9, 75–81.
Dawson, S. and Smith, D.E. (1997) Holocene relative sea-level changes on the margin of a glacioisostatically uplifted area: an example from northern Caithness, Scotland. The Holocene, 7, 59–77.
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. GCR Series No. 16. Joint Nature
Conservation Committee, Peterborough.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Goodier, R. (Ed.) 1975. The Natural Environment of Orkney. Nature Conservancy Council, Edinburgh.
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Hall, A.M. (1996) The Quaternary of Orkney. Field Guide. Quaternary Research Association, Cambridge.
Hansom, J.D. and Evans, D.J.A.1995. Scottish landform examples. The Old Man of Hoy. Scottish
Geographical Magazine, 111, 172–174.
HR Wallingford (2000) Coastal Cells in Scotland. Cell 10 – Orkney. Report to Scottish Natural Heritage,
Scottish Office (Agriculture, Environment and Fisheries Department) and Historic Scotland. Scottish
Natural Heritage Research, Survey and Monitoring Report, No. 151.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Department of
Geography, University of Aberdeen. Countryside Commission for Scotland, Battleby, Perth.
Mather, A.S., Smith, J.S. and Ritchie, W. (1974) Beaches of Orkney. Department of Geography, University
of Aberdeen. Countryside Commission for Scotland, Perth.
May, V. and Hansom, J.D. (in press) Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Mykura, W. (1976) British Regional Geology: Orkney and Shetland. British Geological Survey. HMSO,
Edinburgh.
Nature Conservancy Council (1978) Orkney. Localities of Geological and Geomorphological Importance.
NCC, Newbury.
Ritchie, W. (1984) A Preliminary Study Of The West Coast Of Orkney. Department of Geography,
University of Aberdeen. Unpublished Report to Shell UK.
Simpson, I.A. (1993) The chronology of anthropogenic soil formation in Orkney. Scottish Geographical
Magazine, 109, 4–11.
Simpson, I.A. (1994) Spatial constraints on anthropogenic soil formation in Orkney. Scottish Geographical
Magazine, 110, 100–104.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Page 103
10 January, 2002
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stoker, M. S., Hitchen, K. and Graham, C.C. (1993) United Kingdom Offshore Regional Report: the Geology
of the Hebrides and West Shetland Shelves, and Adjacent Deep-water Areas. London, HMSO for the
British Geological Survey.
de la Vega, A.C. (1998) Flandrian Coastal Environmental Changes: Evidence from Three Sites in Mainland
Orkney, Scotland. Unpublished PhD thesis, Coventry University.
de la Vega, A.C. and Jones, R.L. (1999) Flandrian vegetational changes in Orkney. Orkney Field Club
Bulletin 1999, 20–27.
10
Maps
British Geological Survey 1:50,000 Maps: Sheets 115, 116, 117, 118, 119, 120, 121, 122.
Soil Survey of Scotland Maps: 1:250,000 sheet 1 encompasses Zone 2 and uncoloured 1:50,000 maps
sheets 25, 26 and 30 cover Orkney and sheets 116 and 110 cover North Caithness. MLURI,
Aberdeen.
Page 104
10 January, 2002
ZONE 3
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
WESTERN ISLES
Highlights
Lewisian Gneisses that are among the oldest rocks in the world, including the
occurrence of both poly-deformed orthogneiss and paragneiss.
Evidence of both Scourian and Laxfordian tectonic events.
The largest body of anorthosite in Britain.
Uranium mineralisation and the best opportunities in the UK for studying pegmatite
mineralisation.
The only UK occurrence of the mineral betafite.
Occurrence of the Outer Isles Thrust.
WNW–ESE trending Permo-Carboniferous dyke swarm.
The type locality of the Triassic Stornoway Formation.
A classic example of magmatic differentiation.
The occurrence of the Rockall Granite, which is unique in the UK.
Classic landscapes of glacial erosion (areal scouring) on Lewisian gneiss.
Rare occurrences of pre-last glaciation raised beach.
Evidence for development of local ice cap during last glaciation.
Classic sequences of Quaternary deposits in north Lewis, including some pre-dating last
ice sheet.
Quaternary landforms and deposits on St Kilda and unique land area not covered by last
ice sheet.
Classic example of a ‘drowned’ glaciated archipelago landscape.
Evidence for sea level change in area of limited uplift, including relative abundance of
inter-tidal peat beds.
Only occurrences of strandflats in Scotland.
Diversity of rock coast landforms, from distinctive subdued morphology of gneiss to
highest sea cliffs in Great Britain, at Conachair on St Kilda, and highest sea stack, Stac an
Armin on St Kilda.
Extensive development of machair plains; the type locality for this internationally
important and rare landform.
Diversity of beach/dune/machair landforms; extreme size of dunes and blowouts on Coll
and, elsewhere, exceptional distances and heights to which sand has been blown inland.
Detailed records of Holocene palaeoenvironmental change, human settlement and
human impacts.
Machair soils and large areas of blanket and basin peats.
Machair lochs and streams.
High density of lochs and lochans on the ancient plateaux.
Geology
Apart from a small area around Stornoway, the entire Outer Hebrides and the isles of Coll
and Tiree comprise rocks of the Lewisian Complex. (The gneiss takes it name from the Isle
of Lewis.) Once continuous with the rocks of Western Greenland and north-east Canada,
the Lewisian has experienced a long and complex geological history that began about 3000
million years ago, during the Archaean, early in the Precambrian. Formed form a variety of
rock types, but mostly of igneous origin, the Lewisian Complex has undergone several
episodes of deformation and metamorphism with periods of igneous intrusion. The time
Page 105
10 January, 2002
interval between the formation of the oldest and youngest rocks of the complex might have
been as much as 1200 million years.
The original tectonic event that formed the gneiss is known as the ‘Scourian’, and took place
between 2600 and 2700 million years ago, at the end of the Archaean. This produced the
characteristic grey-banded, high-grade Scourian gneisses. Between 2400 and 2200 million
years ago the Scourian Complex was intruded by basic dyke intrusions, to form the Scourie
Dykes, marking a period of crustal extension. This was followed by a second major tectonic
event, between 2300 and 1700 years ago known as the ‘Laxfordian’, which reworked the
earlier Scourian Complex to give rise to the Laxfordian Complex.
The Lewisian of the Outer Hebrides is thought to have been derived from a complex suite
of igneous rocks that formed around 2900 million years ago. These were subsequently
metamorphosed and deformed during the Scourian event. A significant feature of the
Lewisian of the Outer Hebrides, compared with that of the mainland, is the occurrence of
quite exotic rock types believed to represent metamorphosed equivalents of sedimentary
rocks, such as mudstones and siltstones, in addition to volcanic rocks, such as lavas and
ashes. These supracrustal rocks now form quartzites, marbles, graphitic schists,
kyanite–garnet pelites and amphibolites and form around 5% of the total outcrop on the
Outer Hebrides. The largest and best-displayed outcrops of these supracrustals occurs in
South Harris, around Leverburgh and Langavat. The metasediments, which can also be
referred to as ‘paragneisses’, occur adjacent to the South Harris Igneous Complex
(comprising orthogneisses), which contains the largest body of anorthosite in Britain.
Outcrops of paragneiss also occur at the Butt of Lewis.
Igneous intrusions within the Lewisian complex include several large and important
pegmatites – large granite-like masses with unusual mineralogy; for example, the Chaipaval
Pegmatite at Northton Bay, which occurs within the Leverburgh metasediment belt. This
intrusion yields the uranium-bearing mineral betafite, which is unknown elsewhere in the
UK. This pegmatite offers the best opportunity in the UK to study pegmatite mineralisation,
owing to the occurrence of a rich and diverse mineral assemblage that includes zircon,
tourmaline, topaz, beryl, monaxite, spinel and uraninite.
Like the gneisses of Harris and Lewis, the rocks of Coll and Tiree also contain bands of
metasediment, or paragneiss. Garnet–biotite schists, siliceous schists and a variety of impure
marbles are indicative of ancient sediments having been deposited in the area perhaps as far
back as the Archaean. Among the purer marbles is the Tiree Marble, which has a generally
pink appearance and which has been used as an ornamental stone. Despite similar rock
types and a similar deformational history to other part of the Lewisian Complex, correlation
of the gneisses of Coll and Tiree with other Lewisian areas is uncertain. This suggests
heterogeneity in the deformational regime both during the Scourian and Laxfordian tectonic
events.
The Outer Hebrides and Coll are crossed by numerous shear zones, representing the
effects of tectonic upheavals. These are often associated with retrograde metamorphism
which has altered the characteristic mineralogy of the original high-grade metamorphic rock.
In addition, the gneisses of the Outer Hebrides are cut, in the east, by the Outer Isles fault
zone. The zone extends for 200 km between Sandray to north Lewis and is one of the most
spectacular features in the geology of the Outer Hebrides. It is a high-strain zone and has
been used in the study of formation of mylonites, ultramylonites and pseudotachylites.
Page 106
10 January, 2002
A swarm of dykes, comprising the rocks types camptonite and monchiquite, intruded the
gneisses of the zone during Carboniferous to Permian times. Formed during a phase of
crustal tension thought to represent the first stages in the opening of the North Atlantic,
around 300 million years ago, the dykes are the only rocks in the zone dating from the
Palaeozoic era.
Of considerable significance in the development of the landscape and scenery around
Stornoway is the occurrence of a thick sequence of chocolate-red conglomerates with
subordinate sandstones and rare siltstones, dating from the Triassic period. The Triassic
sequence is seen to rest unconformably upon the Lewisian gneiss at the north of the
outcrop but elsewhere is bounded by normal faults. The sediments represent an onshore
expression of the sedimentary sequence infilling the North Minch Basin, which formed as a
prelude to the opening of the North Atlantic. The conglomerates consist entirely of locally
derived gneiss and many are very coarse, with boulders reaching 1 m and, exceptionally, 3 m
in size. Interpreted as the product of alluvial fan deposition, and known as the Stornoway
Formation, these rocks are an important palaeoenvironmental and palaeogeographic
indicator.
At the start of the Tertiary, the last phase of volcanic activity in Britain began. This activity,
which lasted for around 12 million years, was associated with the splitting of northern
Europe from Greenland and North America, with the formation of the northern North
Atlantic. Evidence for this volcanic activity can be seen all along the western seaboard of
Scotland, the eastern seaboard of Greenland, the western margin of the Rockall Plateau, the
Faeroes and Iceland.
In the Hebrides area, following a phase of fissure eruption style volcanism, which saw huge
outpourings of lava that formed a 3-km-thick lava plateau, volcanism focused upon several
major volcanic centres, for example Rum and Mull. The St Kilda archipelago represents
another such volcanic centre, displaying many of the features seen in the inner Hebridean
volcanoes, including acid and basic igneous intrusions. Lewisian Gneiss, partial melting of
which is thought to have given rise to a portion of the acidic magmas in other centres, is
thought to underlie the St Kilda complex. Rockall, further to the west at the edge of the
continental shelf, represents one of the few occurrences of alkali granite in the British
Tertiary Volcanic Province. Lying within lavas and Cretaceous rocks this small intrusion was
probably formed late in the volcanic episode. The Shiant Isles west of Harris represent a sill
intrusion, a feature common in the British Tertiary Volcanic Province. However, the
intrusion is internationally important for the evidence it provides in the process of magmatic
evolution.
3
Geomorphology
The Outer Hebrides and outlying islands, particularly St Kilda, are of great importance for
interpreting the glacial history and palaeoclimates of the NE Atlantic continental margin.
Much of Lewis, Harris, the Uists, Benbecula and Barra are rocky and ice scoured, similar to
parts of Zone 4, although often mantled in the west by machair. The mountains of Harris
are also similar to parts of Zone 4, with good examples of mountain glacier forms. Glacial
deposits are generally thin and localised, although thicker successions occur along parts of
the coast of NW Lewis, and there are good examples of ‘hummocky’ moraines in the glens
of Harris. There are few meltwater features, the only examples of note being the Glen
Page 107
10 January, 2002
Valtos meltwater channel and the glaciofluvial deposits near Uig. The islands are believed to
have been crossed by mainland ice during an early phase of glaciation, but during the last
glacial stage an independent ice cap was centred on the islands or on the shelf to the west.
Key stratigraphic sections occur along the coast of NW Lewis, and have given rise to
conflicting interpretations. Some workers have proposed that part of northern Lewis
remained ice free during the last glaciation but this now appears unlikely from what is
known about the offshore extent of the ice. However, the summits of Harris probably
existed as nunataks where there are periglacial trimlines. The only other ice-free area of any
extent at the last glacial maximum is likely to have been on St Kilda (see below). Features
pre-dating the last glaciation include a shore platform and organic deposits on the coast of
NW Lewis, raised beaches on the NW coast of Lewis and at Cleit on Barra and organic
deposits at Tolsta Head and NW Lewis. These are all of crucial importance for
understanding landscape evolution during the Quaternary.
During the most intensely cold episodes, ice sheets from the Highlands of Scotland swept
westwards across the continental shelf, which was dry land owing to the lowering of world
sea levels. Whether or not these ice sheets reached St Kilda has been a matter of
speculation, but some evidence from the presence of small rock fragments foreign to the
islands in the deposits around Village Bay suggests that this was possible. The age of such an
ice invasion is unknown, but it pre-dates the last glaciation. At least two periods of valley
glacier development can be recognised on Hirta. An older, as yet undated, ice advance is
represented by glacial deposits at the base of the cliffs at the east side of Village Bay. A
younger ice advance associated with the last glacial maximum around 18,000 years ago
produced moraine ridges along the west side of the glen and deposited a till or boulder clay
in the floor of the glen. During this cold period, the slopes beyond the ice were subject to
intense periglacial weathering. During the Loch Lomond Stadial, protalus ramparts formed in
the glen. The Quaternary geology of St Kilda (glacial and periglacial landforms and the wider
landscape) is considered to be of national (GB) importance, since it is probably the only land
area in Scotland that remained ice-free at the maximum of the last glaciation, apart from
some mountain tops.
The Quaternary sediments and submarine landforms of the adjacent NE Atlantic shelf are of
national and possibly international importance in several respects for the information they
provide on palaeoclimates, ice-sheet dynamics, sea levels, water temperatures, water
circulation and marine biota during the last glacial cycle and its termination. The availability
of high-resolution climate records from the Greenland ice sheet and deep-sea cores in the
North Atlantic now provide unprecedented opportunities to reconstruct glacier responses,
palaeoenvironmental changes and responses of marine biota in a critical and sensitive
location on the maritime fringes of NW Europe. Such work is fundamental in understanding
the coupling of the global atmosphere, oceans and ice sheets during periods of rapid climate
change and the responses in the biosphere in the North Atlantic region. This evidence is
linked with the responses of terrestrial biotas and geomorphological systems as reflected in
palaeoenvironmental records, landforms and deposits at a network of selected sites in the
Western Isles, Inner Hebrides, the Northern Isles and mainland Scotland.
Pollen records show that woodland occurred extensively in the Western Isles from the
early Holocene to about 4400 cal. BP, except in the most marginal areas. Colonisation by
birch and hazel was followed by the spread of oak, elm alder and Scots pine. Woodland
decline occurred in two main phases, after 8800 cal. BP and between 5900–4400 cal. BP, and
the islands were largely treeless by 2600 cal. BP. The development of blanket bog began in
Page 108
10 January, 2002
the early Holocene and expanded during the phases of woodland decline. A site in Gleann
Mór on Hirta contains a valuable pollen record of the vegetation changes that occurred
during the period since the end of the last ice age on the extreme maritime periphery of
Britain. The vegetation history there has been dominated by fluctuations in heathland and
grassland, and there is no evidence for trees or a cover of wood scrub on the island.
Coll and Tiree are Lewisian Gneiss with extensive drift. The drift contains Mesozoic
sediments, so that there is no simple relation between the solid geology and soil
development. Tiree comprises a series of distinctive glaciated shore platforms raised
isostatically above present sea level. Around the coast these are mantled by raised beach
deposits and machair.
The Western Isles, Coll and Tiree exhibit highly distinctive coastlines, the form of which is
controlled partly by the durable Lewisian gneiss bedrock which underlies virtually the entire
zone, and partly by the extreme wave exposure to which west facing coasts are subject.
Particularly characteristic are the machair plains which are developed along many westfacing coasts, in the Uists particularly. Indeed South Uist is the type area for this landform.
Equally distinctive are strandflats – extensive flat surfaces produced by shoreline erosion
during glacial periods – which have recently been described in Coll and Tiree (Dawson,
1994). More typical of Norway, these are the first records of such landforms in Scotland.
Glacial erosion of the gneiss which dominates this area has produced a hummocky rolling
topography of generally low relief across much of the zone. At the coastline, this undulating
topography is expressed in the form of numerous low rocky reefs and skerries, particularly
around the Western Isles which have been subject to gradual but continuous submergence
throughout the Holocene.
On western coasts these are typically punctuated by low cliffs and associated stacks and
arches and, in the Uists especially, by wide sweeping sandy bays backed by machair plains
and, locally, a foredune ridge. Prime examples of these deposits have accumulated on Tiree,
Pabbay, between Ardivachar and Stoneybridge, in South Uist, and along the north-western
coast of North Uist. Towering dunes, exceeding 35 m in height and pitted by vast cauldronlike blowouts, are evident at Crossapol on Coll. These rank among the largest such
landforms in Scotland. The dune-related landforms at Eoligarry in Barra are also exceptional,
with blown sand deposits there blanketing the ground over 100 m above sea level.
In Lewis and Harris, spectacular and renowned beach dune systems also occur, as at
Luskentyre and Scarista, although more typically the beaches are dominated by pebbles and
cobbles. A shingle storm beach often marks the crest of the sandy beaches and/or underlies
the dune ridge. In places, these impound fresh water or brackish lochs on their landward
side. Again this is testimony to rising relative sea level in this area, which is driving beach
material landward over the undulating glaciated landscape.
Within many of the beaches of this zone, inter-tidal peats occur. Such deposits are rare
elsewhere in Scotland and were formed when relative sea levels in this area were lower
than they are now. Through pollen analysis and carbon dating they give a unique insight to
climatic conditions and sea level changes affecting north-west Scotland since the end of the
last ice age.
Page 109
10 January, 2002
The relative lack of wave exposure experienced by east-facing coasts, in the Western Isles
particularly, results in a coastline markedly different from that of the west. In general, the
coastlines facing the Minch have a low and subdued relief of hummocky gneiss bedrock,
forming countless small reefs and skerries interspersed with thin impersistent shingle
beaches and patches of mudflat and saltmarsh. This form of the coastal topography is
typified by the coastline around Loch Maddy and The Sound of Harris, the only drowned
landscape in Scotland designated specifically for that reason. In comparison with west facing
coasts, sandy beaches are poorly developed except at the extreme northern and southern
ends of the coastline where greater wave energy is experienced.
The final distinctive features of these coastlines are the wide intertidal sandflats and strands
which border the channels separating the constituent islands of the Uists. Many of these
channels (such as those linking South Uist, Benbecula and North Uist) have now been
bridged by causeways, leading to some concern regarding the potential knock-on effects on
coastal evolution in their vicinity.
In stark contrast to the coastline of these larger island groups to the east, that of St Kilda is
dominated by soaring cliffs and related landforms cut into a suite of volcanic rocks. The cliffs
at Conachair are the highest in Great Britain, exceeding 450 m. Moreover, at 196 m in
height, Stac an Armin is the highest sea stack in Great Britain.
The most striking freshwater feature of the Western Isles is the extensive network of lochs
and lochans found on the ancient plateau. Boyd and Boyd (1990) state that over 6000 lochs
and lochans are depicted on the 1:63360 Ordnance Survey maps, with more than 100
additional lochs on Coll, Tiree, Ulva and Iona (the last two islands are within the Western
Seaboard, Zone 6). The dominance of lochs on the surface of the Outer Hebrides is clear:
the islands make up 1.3% of the land mass of Great Britain but contain 15% of the total area
of standing water. The vast majority of the lochans have a surface area of less than 0.25 km2,
and 98% of those in the Outer Hebrides are in nutrient-poor catchments (Boyd and Boyd,
1990). The largest lochs by area are Langavat and Suainval (both on the impervious gneiss of
Lewis), 8.9 and 2.4 km2 respectively. The running waters of the Western Isles zone are
relatively short in length. This is primarily a reflection of the small catchments that are found
on many small islands (e.g. Hirta, Vatersay, Coll). Those running off the bare rock plateaux
are mountain torrents with large bed material, are fast flowing and flashy, and have little inchannel vegetation. Streams on the machair, the flat mire platforms and on cultivated land
have smaller bed material, are less flashy and respond to fluctuations in the water-table
rather than directly from rainfall. Machair streams (e.g. on Barra North and South Uist) tend
to have larger catchments and a smaller stream density than those inland (Boyd and Boyd,
1990). Machair areas also have fewer lochans, although they do have machair lochs, which
form close to the sea and have beds of calcareous sands and organic silts, they depend upon
the level of the water-table or receive water from the peaty hinterland, and drain by
seepage through the sand (Angus 1997). Drainage works associated with agricultural
improvement (e.g. on Benbecula) have significantly altered the pattern of inland drainage in
some of the Western Isles by lowering the water-table (Angus, 1997). The drainage patterns
can be quite different among the islands, with variation both between and within islands, e.g.
the eastern sides of North and South Uist are more mountainous than their flatter western
sides, and rivers in the east are mountain torrents rather than the machair streams found in
the west. There are no fluvial geomorphology GCR sites on the Western Isles and no
detailed research has been undertaken into the nature of the fluvial resource.
Page 110
10 January, 2002
4
Soils
The soils are generally nutrient poor, acid and poorly drained; there is widespread
development of peat and associated moorland plant communities. The main exception to
this is the extensive machair along the west coast from North Uist to Barra. This results
from shelly (calcareous) windblown sand deposits which give brown calcareous soils,
calcareous groundwater gleys and calcareous regosols. Soil development is retarded by
climatic conditions, and the two dominant soil groups are surface-water gleys, which cover
54% of the surface, and deep peat, which covers 23% of the islands. Drift material derived
from Lewisian Gneiss tends to produce acidic soils with low nutrient status that, combined
with climatic factors, gives rise to soils with relatively low agricultural productivity. The
most productive soils are found on calcareous coastal deposits, and these soils also support
the most diverse and unique vegetation. Calcareous sands have also been used to improve
nutrient status of acidic soils such as podzols and gleys, and there are many
anthropogenically modified soils. Peat is cut and used as a fuel source, and Lewis in
particular has very large peat reserves in the north of the island. There is localised erosion
of some machair soils, probably due to natural processes and cultivation.
5
•
Summary of key Earth science features in the Western
Isles
The principal Earth heritage interests in the Western Isles are summarised in Table 3.1.
The Western Isles include a total of 34 GCR sites.
Table 3.1
GCR sites in the Western Isles
GCR block
No. of sites
Principal interests
Lewisian
Tertiary Igneous
10
3
Mineralogy
Quaternary of Scotland
6
6
Coastal Geomorphology
9
Representative sections of the Lewisian Gneiss
The remains of a major volcanic centre, rare
rock types and evidence of magmatic
differentiation
Occurrence of minerals rare in the UK
Quaternary geomorphology and stratigraphy,
including pre-last glaciation landforms and
deposits; Holocene sea-level changes and
vegetation history
Outstanding examples of beach, machair and
rock coast landforms
6
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the Western Isles are summarised in Table 3.2. However, there is no
systematic information on current impacts or trends.
Page 111
10 January, 2002
Table 3.2
Potential pressures and vulnerability of Earth heritage interests in the Western Isles
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction and infilling of quarries
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; river management
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Generally robust to all but large-scale developments such as
superquarries
Vulnerable to sand and gravel quarrying, coast protection,
recreation impacts, over-grazing and sea level change
Vulnerable to river engineering and management;
afforestation gravel extraction; land management changes
Vulnerable to land management changes, pollution, peat
erosion
Vulnerable to drainage of bogs and peat
Quaternary depositional landforms
and exposures
Records of sea level change
Rock coast features
Beach and machair systems
Fluvial geomorphology
Soils
Palaeoenvironmental records
7
•
•
8
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
The extent, causes and impacts of coastal erosion on all sand beaches in the Western
Isles were established by HR Wallingford in 1995.
Bibliography
Angus, S. (1997) The Outer Hebrides. The Shaping of the Islands. The White Horse Press, Harris.
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Region 14. South-west Scotland: Ballantrae to Mull. Joint Nature
Conservation Committee, Peterborough.
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Regions 15 and 16. North-west Scotland: The Western Isles and West
Highland. Joint Nature Conservation Committee, Peterborough.
Boyd, J. and Boyd, I.L. (1990) The Hebrides: A Natural History. Collins, London.
Ballantyne, C.K. and McCarroll, D. (1995) The vertical dimensions of Late Devensian glaciation on the
mountains of Harris and southeast Lewis, Outer Hebrides, Scotland. Journal of Quaternary Science, 10,
211–223.
Bennett, K.D., Bunting, M.J. and Fossitt, J.A. (1997) Long-term vegetation change in the Western and
Northern Isles, Scotland. Botanical Journal of Scotland, 49, 127–140.
Bennett, K.D., Boreham, S., Sharp, M.J. and Switsur, V.R. (1992) Holocene history of environment,
vegetation and human settlement on Catta Ness, Lunnasting, Shetland. Journal of Ecology, 80, 241–273.
Cavill, J.E. and Merritt, J.W. (1993) The sand and gravel resources of the Western Isles, Scotland: results
of a reconnaissance survey. BGS Technical Report WA/93.58R.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Dawson, A.G. (1994) Strandflat development and Quaternary shorelines on Tiree and Coll, Scottish
Hebrides. Journal of Quaternary Science, 9, 349–356.
Dawson, A.D. (1999) Assessment of landform change in dune/machair systems of Coll and Tiree.
Unpublished Report to Scottish Natural Heritage, Oban. Department of Geography, University of
Coventry.
Page 112
10 January, 2002
Fyfe, J.A., Long, D. and Evans, D. (1993) The geology of the Malin–Hebrides Sea area. British Geological
Survey, United Kingdom Offshore Regional Report. HMSO, London.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gilbertson, D., Kent, M. and Grattan, J. (Eds) (1996) The Outer Hebrides. The Last 14,000 Years. Sheffield
Academic Press, Sheffield.
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Hall, A.M. (1995) Was north-west Lewis glaciated during the Late Devensian? Quaternary Newsletter, 76,
1–7.
Hambrey, M.J., Fairchild, I.J., Glover, B.W., Stewart, A.D., Treagus, J.E. and Winchester, J.A. (1991) The
Late Precambrian Geology of the Scottish Highlands and Islands. Geologists’ Association Guide, 44.
Hansom, J.D. and Comber, D.P.M. (1996) Eoligarry SSSI documentation and management prescription.
Scottish Natural Heritage Research, Survey and Monitoring Report, No. 49.
HR Wallingford (1995) Survey of coastal erosion in the Western Isles. Unpublished report to Scottish
Natural Heritage, the Western Isles Islands Council and the Minch Project. HR Wallingford Report
EX 3155.
HR Wallingford (2000) Coastal Cells in Scotland. Cell 8 and 9 – The Western Isles. Report to Scottish
Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Department) and Historic
Scotland. Scottish Natural Heritage Research, Survey and Monitoring Report, No. 150. Battleby.
Johnstone, G.S. and Mykura, W. (1989) British Regional Geology: The Northern Highlands of Scotland (4th
edition). British Geological Survey. HMSO, London.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Department of
Geography, University of Aberdeen. Countryside Commission for Scotland, Perth.
Mather, A.S., Smith, J.S. and Ritchie, W. (1974) The Beaches of Northern Inner Hebrides. Department of
Geography, University of Aberdeen. Countryside Commission for Scotland, Perth.
May, V. and Hansom, J.D. (in press) Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Nature Conservancy Council 1977. Outer Hebrides. Localities of Geological and Geomorphological
Importance. NCC, Newbury.
Ritchie, W. (1971) The Beaches of Barra and the Uists. Department of Geography, University of
Aberdeen. Countryside Commission for Scotland, Perth.
Ritchie, W. (1979) Machair Development And Chronology In The Uists And The Adjacent Islands. Proceedings
of the Royal Society of Edinburgh, 77B, 107–122
Ritchie, W. and Mather, A.S. (1970) The Beaches of Lewis and Harris. Department of Geography,
University of Aberdeen. Countryside Commission for Scotland, Perth.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stoker, M. S., Hitchen, K. and Graham, C.C. (1993) United Kingdom Offshore Regional Report: the Geology
of the Hebrides and West Shetland Shelves, and Adjacent Deep-water Areas. British Geological Survey,
HMSO, London.
Sutherland, D.G., Ballantyne, C.K. and Walker, M.J.C. (1984) Late Quaternary glaciation and
environmental change on St. Kilda, Scotland, and their palaeoclimatic significance. Boreas, 13, 261–272.
Sutton, J. and Watson, J. (1951) The pre-Torridonian metamorphic history of the Loch Torridon and
Scourie areas in the North-west Highlands and its bearing on the chronological classification of the
Lewisian. Quarterly Journal of the Geological Society of London, 106, 241–307.
Whittington, G. and Edwards, K.J. (1997) Evolution of a machair landscape: pollen and related studies
from Benbecula, Outer Hebrides, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences,
87, 515–531.
9
Maps
British Geological Survey Maps: 1:50,000 sheets 42, 50, 51, 58, 68, 69, 78, 79, 88, 89, 98, 99, 104, 105,
111.
Page 113
10 January, 2002
Soil Survey of Scotland Maps1:250,000 sheets 2 and 4 encompass Zone 3 and uncoloured 1:50,000
sheets 8, 13, 14, 18, 22 and 31 cover most of the area. MLURI, Aberdeen.
Page 114
10 January, 2002
ZONE 4
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
NORTH-WEST SEABOARD
Highlights
Classic Lewisian Gneiss geology, with some of the oldest rocks in the UK and
worldwide.
The principal outcrop area of the Torridonian Sandstone.
The oldest fossils in Britain.
The northwestern extent of the Moine succession.
Classic Cambrian–Ordovician sedimentology and stratigraphy that demonstrates
Laurentian continental margin sedimentation.
A Cambrian–Ordovician fossil fauna that has a distinct North American affinity.
Classic localities illustrating the intricacies of the Moine Thrust.
The only plutonic complex composed largely of silica-undersaturated igneous rocks in
the UK.
The north-westernmost extent of Triassic rocks on the UK mainland.
The location of seminal work by the geologists Peach, Horne and Watson.
The occurrence of a unique assemblage of relict landforms, including erosion surfaces,
scarps and inselbergs, indicative of long-term landscape evolution.
Glacial landforms and landscapes, including classic landscapes of glacial erosion (areal
scouring), the type area for the Wester Ross Readvance, the occurrence of a trimline
and nunataks associated with the last ice sheet and classic examples of Loch Lomond
Readvance mountain glaciation deposits.
Outstanding examples of periglacial landforms developed on Torridonian sandstone.
The most extensive and best developed cave and karst systems in Scotland, providing a
unique record of landscape development during the Quaternary.
Unique faunal and palaeoenvironmental records from the Inchnadamph caves.
Detailed records of Holocene palaeoenvironmental change, including forest history and
human impacts on the landscape.
Exceptional dynamism of coastal beach/dune systems as at Sandwood Bay and Faraid
Head.
Most mainland occurrences of machair.
The highest sea cliffs on the UK mainland, at Cul More.
Relatively undisturbed catchments and river channel planforms.
Short, steep, westerly flowing rivers, with longer rivers flowing north and displaying
downstream channel change.
Geology
Zone 4 is one of the few zones where the zonal boundary corresponds to a certain extent
to a geological boundary, in this case the Moine Thrust Zone – an important geological
structure that runs approximately parallel to the coast, about 20–30 km inland. To the west
of the Moine Thrust, the geology is characterised by low-lying Lewisian Gneiss, and
mountainous areas comprising Torridonian Sandstone. East of the Moine Thrust, the upland
areas are made up of Moine Schists. Along the Moine Thrust itself, there is the
Cambrian–Ordovician rock sequence of the Northwest Highlands that includes the famous
Durness Limestone, often conspicuous in giving rise to lush vegetation, on base-rich
(especially calcium) soils. The geology of this zone is not only of national significance but is
of international significance. The work by Sutton and Watson on the Lewisian Gneiss, and
the earlier work on the general stratigraphy and the Moine Thrust Zone by Peach and
Page 115
10 January, 2002
Horne, has been crucial in the development of studies in high-grade gneiss terranes and
thrust belts worldwide. Studies on the Cambrian–Ordovician sequences have helped prove
the existence of the Iapetus Ocean.
Of the four major groups of rocks forming the landscape of the zone, the Lewisian Gneisses
are the oldest. Underlying most of the northern part of the zone from Enard Bay to Cape
Wrath, with southern outcrops around Loch Maree and Loch Torridon, these rocks are
named after the Isle of Lewis, where they predominate. Much of the Lewisian Gneiss, which
is the oldest group of rocks in Britain, dates back to the Archaean, a period in Earth history
that ended around 2500 million years ago. The Lewisian Gneiss, demonstrated in sections
along the Scourie Coast, was formed as a result of several major tectonic events that
repeatedly metamorphosed and deformed what were originally ancient igneous and
sedimentary rocks. Such was the intensity of metamorphism, that nothing remains of their
original sedimentary and igneous structure, or the microscopic fossil life present in the
Archean; geochemistry is the only tool for elucidating the original rock character.
Around 1500 million years ago, the Lewisian Gneiss underlying the zone represented the
bedrock of the south-eastern edge of a continental landmass called Laurentia. Laurentia
incorporated the Northwest Highlands of Scotland, and much of what is now Greenland and
North America. Erosion of the Lewisian bedrock making up the Laurentian landmass gave
rise to vast quantities of sand and other sediment, which was washed southward across the
area that is now the Northwest Highlands. Current understanding is that deposition of the
sediment took place over hundreds of millions of years, giving rise to the vast sedimentary
sequences known as the Moine Assemblage and the Torridonian Sandstone.
Named after the peninsula of a’Mhoine in northern Sutherland, the Moine Assemblage is
composed of three distinct Divisions: the Morar Division, the Glenfinnan Division and the
Loch Eil Division. The precise relationship between the three divisions is still being debated,
but the Morar and Loch Eil Divisions are regarded as the oldest and the youngest
respectively. The Morar Division underlies the landscape of the eastern margins of the zone.
The sediment making up the Moine Assemblage is thought to have accumulated over several
hundred million years, between 1500–1050 million years ago, to form a pile several
kilometres in thickness upon the ancient Lewisian Gneiss; the Loch Morar Division itself
reaches in excess of 6 km. After the deposition of the sediment pile, the collision of
continental landmasses, through the mechanism of plate tectonics, deformed and
metmorphosed the sediments. The metamorphic and deformational history of the Moine
Assemblage was complex, and there were several phases of mountain building, or orogeny,
resulting from continental collision, starting around 1000 million years ago. The various
sedimentary rocks were metamorphosed to schists and gneisses, with the recrystalisation of
sandstones to quartzites and the more muddier sediments to pelites. The metamorphism
was not entirely uniform, with the result that some portions of the Assemblage were
subjected to high-grade metamorphism resulting in the formation of gneisses, whereas other
areas escaped relatively unscathed with the preservation of the features characteristic of the
original sedimentary rock, such as layering and dune-bedding. In places the rocks have been
metamorphosed to such a high grade that they were close to melting point and show
evidence of having behaved as a plastic during deformation. These high-grade metamorphic
rocks are known as migmatites.
Page 116
10 January, 2002
The Torridonian Sandstone, in contrast to the Moine rocks, is relatively undeformed and
has not been subjected to successive metamorphic events. Although originating as loose
sediment on the south-eastern margin of the Laurentian continent, the Torridonian is
younger than the Moine and was deposited over a 200-million-year period between 970 and
700 million years ago. Formerly thought to have formed contemporaneously with the
Moine, the precise relationship between the Moine and the Torridonian is still poorly
understood.
The Torridonian of the zone is subdivided into two distinct groups, the older Stoer Group
and the younger Torridon Group. Deposited 200 million years apart, the Stoer and
Torridon Groups represent sediment deposited in rift valleys that developed on the
Laurentian continental margin. Before the deposition of the Torridon Group, the Stoer
Group was tilted to the north-west by 30 degrees and extensively eroded, so that over
much of the area the Torridon Group now rests directly, and unconformably, on Lewisian
Gneisses. The lowermost sediments of both groups infill valleys and generally smother the
landscape that had been eroded into the old gneisses. The lack of subsequent
metamorphism of the sediments has meant that all of the original features of the sediments,
including layering, dune-bedding, mudcracks, rain prints and some microscopic fossils, are
often perfectly preserved, revealing a lot of information concerning the precise
environmental conditions in which the sediment was laid down. Minor amounts of volcanic
rock within the Torridonian sedimentary sequence, such as volcanic ash, which would have
been obliterated by metamorphism, are testimony to crustal instability at the edge of the
Laurentian continent. Stunning sections of the Torridonian Sandstone occur in places such
as Enard Bay, Aultbea and Cailleach Head.
Although the Torridonian and underlying Lewisian were not subjected to metamorphism in
the 200 million years before the start of the Cambrian period, the area was subjected to a
period of folding. Considerable erosion followed the folding and several hundred metres of
Torridonian rock were removed in places to lay bare the underlying Lewisian Gneiss. By the
beginning of the Cambrian times, erosion had produced a remarkably flat surface passing
across hard gneiss and sandstone alike; this may have been formed by marine erosion.
Cambrian sediments were deposited on this surface as it progressively and gently subsided
to form the floor of a shallow shelf sea. This shelf lay on the south-east side of the Laurentia
continental landmass which bounded the Iapetus Ocean on its north-west side.
The remains of the Cambrian and Ordovician age sediments laid down in this shallow sea
now occupy a narrow band up to 20 km across that runs the length of the zone and which
parallels the boundary. This sedimentary rock pile divides simply into a lower suite of rocks
comprising sandstones, siltstones and mudstones, and an upper carbonate, or limestone,
sequence. Little variation in thickness has been detected along the length of the exposure,
and 1500 m has been given as a probable maximum thickness for the whole sequence. The
succession is well seen at only a few places. In the north, an almost complete sequence can
be obtained around Durness and Loch Eriboll; to the south, although broken up by faulting,
parts of the sequence are well exposed in the Assynt area and in the neighbourhood of
Ullapool and Kinlochewe.
The sandstones at the base of the sequence, which include the famous Pipe-Rock, are
interpreted as having formed in shallow tidally influenced marine conditions; the ‘pipes’
represent worm burrows. The carbonate-rich siltstones and shales of the overlying Fucoid
Beds record a lagoonal environment superimposed upon the tidal sandstones below. The
Page 117
10 January, 2002
Salterella Grit at the top of this lower suite is composed of sandstone. Filled with the
remains of fossil gastropod shells, the Salteralla Grit is thought to have formed a linear sand
body in the marine environment. The upper carbonate, or limestone, sequence forms the
bulk of the Cambrian–Ordovician sequence, and comprises the seven formations of the
Durness Limestone. Formed in tidal flat and shallow marine conditions, the limestone was
derived largely through chemical precipitation of carbonate from the sea water. The
junction between the Cambrian and Ordovician systems lies within the Durness Limestone.
By the Silurian period, the once great Iapetus Ocean was closing, bringing together the two
continental landmasses on either side. This closure brought about an event known as the
Caledonian Orogeny, which metamorphosed and deformed the sedimentary sequences and
the underlying rock on the continental margins of the Iapetus. Although almost all of the
area that is now Scotland was affected, the rocks within the western part of Zone 4 lay
outwith the area that experienced the most intense metamorphism and deformation.
However, the zone does contain one of the most famous geological structures of the
Caledonian Orogeny, the Moine Thrust. Thought to extend for over 500 km, the Moine
Thrust formed late in the Orogeny around 430 million years ago.
The Moine Thrust formed as compressive forces, directed upwards and outwards from the
point of continental collision, pushed previously metamorphosed Moine rock northwestwards over the Cambrian–Ordovician sedimentary sequence and Lewisian Gneiss. The
Moine Thrust, magnificently illustrated at Knockan Cliff, is the most important single thrust
fault in a zone of low-angle thrust faults that make up the Moine Thrust Zone. It is thought
that the Moine rocks moved around 70 km over the rocks to the west along these lowangle thrusts. Movement along the thrust planes produced a localised, highly deformed rock
type known as mylonite. Within the Moine Thrust Zone in the vicinity of Assynt, the Loch
Borralan and Loch Ailsh Complexes represent igneous rock that formed in association with
the Caledonian deformation. Composed of syenite, these igneous intrusions, derived
through melting of rock at depth, are rich in potassium, giving rise to nutrient-rich soils with
moderate to high pH. The intrusions are not only unusual in a UK context, but are of
international significance owing to the occurrence of rock types that are extremely rare on
a worldwide scale.
There are no Devonian or Carboniferous rocks within the zone, although there is no
evidence to suggest that deposition of sediment did not take place during this time. During
Permian and Triassic times an arid climate prevailed, and red sandstones and conglomerates
were deposited in alluvial fans and in the low-lying plains of ephemeral rivers. Small
exposures of Triassic rocks within the zone, between Gruinard and Loch Ewe, at Gairloch
and in Applecross, are testimony to this period in Earth history. Patches of Jurassic rocks at
Gruinard and Applecross document the inundation of the area by shallow tropical seas
around 190 million years ago.
3
Palaeontology
Fine-grained Torridonian sediments of Precambrian age, deposited in lacustrine
environments, have yielded the remains of 800- to 900-million-year-old micro-fossils. These
are simple aquatic organisms such as filamentous cyanobacteria and are the oldest fossils in
Britain.
Page 118
10 January, 2002
The Cambrian–Ordovician shallow marine shelf sequences have yielded a rich and diverse
fossil fauna. In addition to gastropods and worms, which are very evident in the Salterella
Grit and Pipe-Rock respectively, the sequence yields other fossils, including brachiopods,
cephalopods, trilobites, sponges and conodont animals. Being on the northern margin of the
Iapetus Ocean, this fauna resembles that of the North American Province and shows a
marked contrast with that found in the rocks of similar age in England and Wales, which
were laid down on the south shore of the Iapetus.
Lower Jurassic sequences at Applecross and between Gruinard and Loch Ewe yield the
fossils of marine animals including ammonites, vital in Jurassic biostratigraphy.
4
Geomorphology
The low coastal plateaux of NW Scotland are made up of extensive ice-scoured surfaces,
known as ‘cnoc and lochan topography’, the form of which is strongly controlled by the
underlying geological structures. The Lewisian gneiss, in particular, forms a rough, irregular
topography, part of an ancient land surface exhumed from below the cover of Torridonian
rocks. Where the Torridonian forms the lower ground, the more gently dipping beds give
rise to a more subdued topography; the contrast is particularly well exemplified between
Handa (Torridonian) and the adjacent mainland (Lewisian gneiss). In Sutherland and Wester
Ross, the major hills occur as isolated mountain massifs of Torridonian sandstone rising
above the ice-scoured Lewisian plateaux. These residual mountains form the remains of an
ancient dissected scarp front. The mountains are among the most intensively ice scoured in
Scotland and the landscape has been shaped by ice sheets, mountain icefields and corrie
glaciers during the many episodes of cold climate during the Quaternary ice age of the last 2
million years. The glaciers have exploited pre-existing valleys aligned along NW–SE lines of
structural weakness, forming glacial troughs that have been drowned in their lower reaches
to form fjords and sea lochs. Inland, pre-existing watersheds were breached by the ice,
forming through valleys linking the west and east coasts. Glacial deposits are generally thin
and localised, but are thicker and have greater topographic expression within the limits of
the Loch Lomond Readvance, e.g. in Torridon. Many of the corries and glens also have
particularly fine examples of a range of moraine types. In Wester Ross, between Applecross
and Gairloch, the Wester Ross Readvance moraine forms a striking linear feature that is
believed to mark a halt in the recession of the last ice sheet. Most of the mountain summits
have been modified by periglacial processes. In a number of cases, there is a clear lower
limit to the occurrence of frost-weathered bedrock, and ice-scoured bedrock below,
marking what is interpreted as a trimline of the last ice sheet and indicating that these
summits existed as nunataks. Assemblages of periglacial features occur widely on the
mountains and are especially well developed on An Teallach. A number of large rock slope
failures exist in the area, including a notable feature on Beinn Alligin associated with glacier
ice.
A distinctive feature of the geomorphology of this zone is the occurrence of karst and cave
landforms in the Durness and Assynt areas. Of these, the latter is nationally important for
its assemblage of glaciokarst features and the longest cave systems in Scotland. These caves
include important geomorphological records of the evolution of the region. Some of the
caves (the Bone Caves) have also yielded exceptional faunal remains extending back to the
time of the last ice age.
Page 119
10 January, 2002
Sea level changes around the coasts have not been studied in detail. After the phase of high
sea level accompanying ice-sheet decay, there appears to have been a long period when sea
level was below that of the present, and the only evidence for later higher sea levels is the
sequence of beaches formed at the maximum of the Main Postglacial Transgression and
subsequently. None of these shorelines has been dated, although by comparison with
elsewhere in Scotland they can be presumed to have been formed during approximately the
last 6000 years.
The rapid climatic amelioration at the start of the Holocene was marked by a vegetation
succession from dwarf-shrub tundra, through a juniper-dominated phase to the expansion of
birch and then birch-hazel woodland (as documented in the pollen records at Loch Maree
and Loch Sionascaig, for example). Latterly to the south of the region, communities of oak
and elm became established in favourable localities, but by around 8300 14C yr BP pine
appeared, apparently earlier at certain sites in Wester Ross and farther north (Loch Maree)
than at sites farther south, and even earlier than at neighbouring sites in the region (Loch
Clair). In the northern part of the region there was probably only a brief phase of pine
expansion in what was predominantly a birch forest zone (as represented in the pollen
record at Lochan an Druim). Reduction in the forest cover began around 5000–4000 14C yr
BP, with accompanying expansion of blanket bog, possibly a result of a climatic change to
cooler and moister conditions. The role of human activity in this process, although apparent
farther south, remains to be clearly demonstrated in this region. Extensive clearance of
birch forest in the last 1500 years can be more directly attributed to human activity.
The coastline of this zone is dominated by two contrasting rock types, each of which exerts
a distinctive influence on the nature of the coastal landforms which exist there.
From Faraid Head west to Cape Wrath and south to Enard Bay, hard, resistant Lewisian
gneiss is the principal bedrock and consequently the coastline resembles, broadly, that of
Zone 3, the Western Isles, dominated by low, rocky reefs and skerries. Cliffs are also
commonplace; although generally low, those at Cul Mor, east of Cape Wrath, attain 280 m,
making them the highest on the UK mainland.
In this area, outliers of Torridonian Sandstone and Cambrian Quartzites outcrop within the
gneiss. The less durable lithology and blockier fracture of these strata produce more angular
cliffs than does the gneiss and more extensive scree slopes at their base. Through their
erosion, these rocks also contribute more sediment for beach formation, locally, than do
the Lewisian and Moine formations. Around Durness, limestone outcrops at the coast. One
consequence of this is the 60-m-long Smoo Cave, the vast outer chamber of which is 37 m
wide by 12 m high.
Around this north-west corner of Scotland, sand has collected in many of the bays to form
beaches of stunning beauty, none more so than the outstanding Sandwood Bay. Most of the
mainland examples of machair also occur within this zone, as for instance from Sheigra to
Oldshoremore and Oldshorebeg. The extreme exposure to which many of these systems
are subject also makes them exceptionally dynamic. Particularly notable in this respect are
the highly dissected dunes at Sandwood and the great drifts of bare sand that blanket Faraid
Head near Durness.
South of Enard Bay, Torridonian Sandstone becomes the principal bedrock outcropping at
the coast. These shores are, in addition, more protected from the extremes of wave energy
Page 120
10 January, 2002
experienced further north, as a result of the sheltering effects of the Western Isles. In
consequence, erosive landforms such as cliffs, and high-energy depositional features such as
beaches, are less well developed than in the far north, with a few notable exceptions such as
Gairloch and Applecross. Instead, the coastline is dominated by long, narrow sea lochs that
extend inland between mountain ranges. Seawards these may be guarded by low, rocky cliffs
and reefs but inland their shores are most often characterised by thin, shingle beaches and,
at their heads, saltmarshes as, for example, in Loch Torridon.
The far north-west corner of Scotland around Cape Wrath is one of the most remote areas
of the country and, in consequence, streams and rivers there are in a relatively undisturbed
or pristine state. Despite this, little research into river processes has been undertaken
there. The Cape Wrath peninsula has a watershed approximately parallel to the coast, and
streams flowing west from the watershed, including the Keisgaig river, end in waterfalls or
reach the sea via rocky ravines. The majority of these streams are short and fast flowing. In
contrast, the Abhainn an t-Srathain is a major river, which, unusually for the mainland, ends
in a machair loch. The River Dionard is the major north-flowing gravel bed river in the Cape
Wrath peninsula, displaying downstream channel change and development consistent with a
well-developed fluvial system. The upper-middle reaches have tight, irregular meanders with
cut-offs (this is possibly in an alluvial basin). Downstream, a wider meander train displays
evidence of marsh and overbank flows, and the river finally becomes sinuous near the Kyle
of Dionard.
In Assynt and the other western seaboard peninsulas there is a high density of lochs and
lochans, generally aligned north-west to south-east, with interconnecting rivers also
following this alignment. This is the cnoc and lochan topography described previously. The
major rivers in Assynt are the River Inver, which drains Loch Assynt, and the Kirkaig, which
drains Loch Vayetie. Hydro-electricity is generated on the River Canaird below the
confluence with the River Runice. In the southern part of the zone the upper reaches of the
Dundonnel River (above the A832) flows through an alluvial basin and has a number of
waterfalls and tight meanders in the upper reach. The catchment of the Loch Maree,
Kinlochewe and Ewe rivers is one of the largest in the North-West Seaboard, and waterfalls
and meandering and divided planforms can all be found along this system. The
Corrieshalloch Gorge waterfall, a slot-sided gorge cut by glacial meltwater streams, is a
notable GCR site within the Loch Broom catchment. The River Applecross shows a range
of planforms downstream from divided in the upper-middle reaches to sinuous in the lower
reaches.
The lack of fluvial geomorphology GCR sites in this zone is probably a function of the lack
of detailed research into fluvial processes in this area rather than a comment on the quality
of the river systems, as this zone contains many of Scotland’s undamaged/relatively
unmodified rivers and undoubtedly provides opportunities for research.
5
Soils
Soils are formed on a wide range of drift materials, mostly coarse grained and acidic. In a
few isolated places where the drift is derived from ultrabasic materials, the soil chemistry
reflects the increase in free magnesium, calcium and potassium. In general, leaching of acid
parent drift material gives rise to base-deficient, acid soils that are sandy- to coarse-textured
(podzolic soils); at sites where drainage below the surface is impaired, surface-water gleys
Page 121
10 January, 2002
occur. Many soils are poorly drained, either because of the nature of the parent rock
(crystalline basement) or because of the common development of indurated horizons (on
the sandstones), resulting in up to 65% of soils in this zone being classified as surface-water
gleys. The surface accumulation of acid organic matter gives rise to widespread peat
development and typical moorland plant communities. There are also soils formed on
calcareous machair deposits in coastal areas and a number of alpine/sub-alpine soils in the
uplands. In addition, there are some calcareous parent materials which give rise to more
base-rich brown rendzinas, for example in the Durness and Inchnadamph areas. The alpine
brown soils developed on Ben Eighe are also of restricted national occurrence.
6
Summary of key Earth science features in the North-West
Seaboard
The principal Earth heritage interests in the North West Seaboard are summarised in Table 4.1. The
North-West Seaboard includes a total of 65 GCR sites.
Table 4.1
GCR sites in the North-West Seaboard
GCR block
No. of sites
Principal interests
Lewisian
Torridonian
12
8
Moine
Cambrian
14
2
Representative sections of the Lewisian Gneiss
Key representative sections of the Torridonian
Sandstone
Representative sections of the Moine Assemblage
Classic and representative Cambrian sedimentary
sequences of the Northwest Highlands
Classic Cambrian to Ordovician sedimentary
sequences
Igneous rocks formed as a result of the Caledonian
Orogeny – some of which are of international
significance
A key section of Permian to Triassic age
sedimentary rocks
The most comprehensive Middle and Late
Devensian fauna in Scotland; unique records of
palaeoenvironmental change
Classic glacial and periglacial landforms, and key
reference sites for Lateglacial and Holocene
vegetation history and environmental change
Dynamic beach/dune/machair system
Scotland’s finest karst landforms
The most extensive and best developed cave
systems in Scotland, providing a unique record of
landscape development during the Quaternary
Classic example of a gorge formed by glacial
meltwater rivers and showing close relationship to
geological controls
Cambrian and Tremadoc
Caledonian Igneous
1
11
Permo-Trias
1
Vertebrate Palaeontology
2
Quaternary of Scotland
9
Coastal Geomorphology
Karst
Caves
1
1
2
Fluvial Geomorphology
1
Page 122
10 January, 2002
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the North-West Seaboard are summarised in Table 4.2. However, there is
no systematic information on current impacts or trends.
Table 4.2
Potential pressures and vulnerability of Earth heritage interests in the North-West
Seaboard
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction and infilling of quarries
Palaeontological interests
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Quaternary depositional landforms
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments; land
management changes; construction of tracks; afforestation;
river management
Periglacial geomorphology
Vulnerable to enhanced erosion through overgrazing and
increased recreational pressures
Cave and karst landforms and deposits Vulnerable to drainage changes, irresponsible caving or
collecting, removal of limestone pavement
Records of sea level change
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Rock coast features
Generally robust to all but large scale developments such as
superquarries
Beach, dune and machair landforms
Vulnerable to mineral extraction from beaches; coast
protection; commercial and industrial developments, land
claim, overgrazing and sea level rise
Palaeoenvironmental records
Vulnerable to drainage of bogs and peat extraction
Soils
Vulnerable to land management changes, pollution
8
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Fossils, particularly trilobites are collected from the Cambrian/Ordovician exposures.
Bibliography
Ballantyne, C.K., Sutherland, D.G. and Reed, W.J. (1987) Wester Ross Field Guide. Quaternary Research
Association, Cambridge.
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1996) Coasts And
Seas Of The United Kingdom. Region 3. North-east Scotland. Cape Wrath to St Cyrus. Joint Nature
Conservation Committee, Peterborough.
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Regions 15 and 16. North-west Scotland: the Western Isles and west Highland.
Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Crofts, R. and Mather, A.S. (1971) The Beaches of Wester Ross. Perth, Countryside Commission for
Scotland.
Page 123
10 January, 2002
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Hambrey, M.J., Fairchild, I.J., Glover, B.W., Stewart, A.D., Treagus, J.E. and Winchester, J.A. (1991) The
Late Precambrian Geology of the Scottish Highlands and Islands. Geologists’ Association Guide, 44.
HR Wallingford (2000) Coastal cells in Scotland. Cell 4 – Duncansby Head to Cape Wrath. Report to
Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Department) and
Historic Scotland. Scottish Natural Heritage Research, Survey and Monitoring Report, No. 146.
HR Wallingford (2000) Coastal cells in Scotland. Cell 5 – Cape Wrath to the Mull of Kintyre. Report to
Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Department) and
Historic Scotland. Scottish Natural Heritage Research, Survey and Monitoring Report, No. 147.
Johnstone, G.S. and Mykura, W. (1989) British Regional Geology: The Northern Highlands of Scotland (4th
edition). British Geological Survey, HMSO, London.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Department of
Geography, University of Aberdeen. Countryside Commission for Scotland, Perth.
May, V. and Hansom, J.D. (in press) Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Peach, B.N., Horne, J., Gunn, W., Clough, C.T., Hinxman, L.W. and Teall, J.J.H. (1907) The Geological
Structure of the North-west Highlands of Scotland. Memoir of the Geological Survey of Great Britain.
Ritchie, W. and Mather, A.S. (1969) The Beaches of Sutherland. Department of Geography, University of
Aberdeen. Countryside Commission for Scotland, Perth.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Sutton, J. and Watson, J. (1951) The pre-Torridonian metamorphic history of the Loch Torridon and
Scourie areas in the North-west Highlands and its bearing on the chronological classification of the
Lewisian. Quarterly Journal of the Geological Society of London, 106, 241–307.
Waltham, A.C., Simms, M.J., Farrant, A.R. and Goldie, H.S. (1997) Karst and Caves of Great Britain.
Geological Conservation Review Series No. 12. Chapman and Hall, London.
10
Maps
British Geological Survey Maps: 1:50,000 sheets: 81, 82, 91, 92, 101, 107, 108, 113, 114.
Soil Survey of Scotland Maps: 1:250,000 sheet 3 encompasses Zone 4 and uncoloured 1:50,000 sheets 9,
15 and 19 cover most of the area. MLURI, Aberdeen.
Page 124
10 January, 2002
ZONE 5
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
THE PEATLANDS
SUTHERLAND
OF
CAITHNESS
AND
Highlights
Lewisian Gneiss inliers.
High-grade metamorphism of the Moine Assemblage.
Caledonian thrust tectonics.
Devonian sedimentary sequences.
Triassic sedimentary sequences.
Classic sections of the Kimmeridge Clay.
Furthest north workable deposits of coal and brick clay.
Type locations for both fossil fauna and flora.
Erosion surfaces and inselberg landforms reflecting long-term landscape evolution.
Glacial deposits, including erratic materials derived from offshore, that provide evidence
for the pattern and timing of the last ice-sheet glaciation.
Palaeoenvironmental records of Holocene forest history, peat development and human
impacts on the landscape.
Complex association of coastal, glacial and postglacial landforms at Invernaver, including
exceptional and extensive development of ‘climbing dunes’.
Flow Country mire complex.
River Helmsdale, site of Scotland’s mini ‘gold rush’.
Dendritic drainage system through peat.
Subsurface drainage system through glacial drift resulting in surface erosion.
Geology
Zone 5 contains a wide variety of rocks types of widely differing ages. The oldest rocks are
slivers of ancient Lewisian Gneiss, more commonly found in the zones to the west. These
ancient rocks form the foundation upon which lie the younger rocks of the Moine
Assemblage. The Moine itself underlies most of Zone 5 and represents a series of ancient,
shallow marine sediments, shales, siltstones and sandstones deposited onto already
deformed and metamorphosed Lewisian Gneiss between 1000 and 850 million years ago.
After the deposition of the sediment pile, the collision of continental landmasses, through
the mechanism of plate tectonics, deformed and metamorphosed the Moine sediments. The
metamorphic and deformational history of the Moine Assemblage was complex and there
were several phases of mountain building, or orogeny, resulting from continental collision,
starting around 1000 million years ago. The various sedimentary rocks were
metamorphosed to schists and gneisses, with the recrystalisation of sandstones to quartzites
and the more muddy sediments to pelites. The Moine, together with the underlying
Lewisian rocks, was subsequently deformed again during the Caledonian Orogeny, a major
mountain-building episode between 470 million and 430 million years ago.
Before the Caledonian Orogeny, during the Cambrian and Ordovician Periods, sediments
were deposited on an eroded surface of Lewisian Gneiss, west of where the Moine
Assemblage lay. This deposition took place on a shallow sea on a continental shelf on the
south-east side of a continental landmass referred to as Laurentia, which represented the
north-western margin of the Iapetus Ocean.
Page 125
10 January, 2002
The remains of the Cambrian and Ordovician age sediments laid down in this shallow sea
occur at several locations along the western margin of the zone, at Loch Eriboll in the north
and Loch Urigill in the south. This sedimentary rock pile consists of a lower suite of rocks
comprising sandstones, siltstones and mudstones, and an upper carbonate, or limestone
sequence. A probable maximum thickness for the whole sequence amounts to several
hundred metres.
The sandstones at the base of the Cambrian sequence, which include the famous Pipe-Rock,
are interpreted as having formed in shallow tidally influenced marine conditions; the ‘pipes’
represent the burrows of worms. The carbonate-rich siltstones and shales of the overlying
Fucoid Beds record a lagoonal environment superimposed upon the tidal sandstones below.
The Salterella Grit at the top of this lower suite comprises sandstone. Filled with the
remains of fossil gastropod shells, the Salterella Grit is thought to have formed a linear sand
body in the marine environment. The upper carbonate, or limestone, sequence forms the
bulk of the Cambrian–Ordovician sequence, and comprises the seven formations of the
Durness Limestone. Formed in tidal flat and shallow marine conditions, the limestone was
derived largely through chemical precipitation of carbonate from the sea water. The
junction between the Cambrian and Ordovician systems lies within the Durness Limestone.
The closure of Iapetus during Ordovician and Silurian times, with the onset of the
Caledonian Orogeny, brought about metamorphism of the Moine Assemblage and
shortening of the crust, in part through movement of rock sequences along huge fault lines.
This had the effect of chopping up the Lewisian, Moine and the recently deposited Cambrian
and Ordovician sequences into huge slabs that piled up one upon the other. This mountainbuilding event was associated with the ‘coming together’ of the various crustal fragments
that make up Scotland, and ultimately continental collision with a continental fragment
carrying England, Wales, Southern Ireland and parts of north-west Europe.
The deformation during the Caledonian Orogeny divided the Moine into a series of principal
structural units, each bound at its base by a major structural break or geological fault. From
west to east these are the Moine Thrust, the Naver Thrust and the Swordly Thrust. These
thrust, or fault-bounded rock units, were ‘shunted’ from east to west. The Moine rocks at
the east of the zone have experienced greater temperatures and pressures during
metamorphism than the westernmost portions of the Moine. Consequently, the
‘metamorphic grade’ recorded in the Moine rocks increases from west to east.
During the orogeny, areas of the ancient Lewisian were infolded in to the overlying Moine
and these occur in a N–S zone between Bettyhill and Loch Shin. In addition, as a result of
high metamorphic grades east of the Naver Thrust, large areas of Moine were partially
melted (migmatised). Such areas coincide with the large migmatitic complexes of Strath
Halladale and Loch Coire. The Lewisian comprises basic or ultrabasic rock, and, as such,
may show a marked influence upon the flora compared with the relatively nutrient poor
Moine.
One of the major geological features in the west of the zone is the Moine Thrust Zone,
which is a geologically complex area through which the zone boundary passes, crosses and
re-crosses. The Moine Thrust Zone is a fundamental break in Highland geology. The Sole
Thrust, marking its base, represents the western limit of deformation associated with the
Caledonian Orogeny. The Moine Thrust itself forms the western limit of the Moine
Assemblage. The zone contains a wide variety of rock types representing the telescoped
Page 126
10 January, 2002
remains of a Cambrian and Ordovician shallow marine shelf and parts of its basement.
Unravelling the deformed sequence would restore the rocks to their original horizontal
expression – a length of some 100 km.
At the eastern limit of the zone there occur several internationally significant igneous
intrusions, which occur largely in the adjacent Zone 4. These are intrusions of an alkali
character found within the Moine Thrust Zone itself (Loch Borralan and Loch Ailsh) and to
the east of the Moine Thrust, forming Ben Loyal. They are made up of a wide range of
syenites, some for which this is the type locality – assynite, ledmorite and borralonite. The
Loch Borralan intrusion has been used to date thrust movement in the Moine Thrust Zone.
Associated with the Loch Borralan complex, and found along the shore of Loch Urigill, is a
rock type rare in Britain – carbonatite. In the east of the zone there is a series of granitic
intrusions associated with melting of lower portions of the crust as a consequence of the
orogeny: Rogart, Helmsdale and Migdale.
The Moine in the east of the zone is overlain by rocks originally laid down as loose sediment
during the Devonian Period. Sometimes referred to as the Old Red Sandstone, these rocks
represent river and alluvial fan deposits deposited under arid conditions in the shadow of
the Caledonian mountains. The unconformity, or horizontal boundary between the
Devonian sediments and the Moine, is well exposed on the coast west of Portskerra.
Numerous outliers of Devonian sandstone occur throughout the zone, e.g. at Meall Odhar,
Ben Griam More, Ben Griam Beg and particularly the Brora Outlier. The Lower Devonian
sequences give way to Middle Devonian in the east of the zone, the Devonian forming part
of a major offshore basin to the north.
Pockets of sedimentary rocks deposited during Permian and Triassic times occur as outliers
within the Kirtomy and Tongue area, as well as forming Eilean nan Ron.
The Helmsdale Fault, in the east of the zone, runs from Helmsdale to Brora in the south.
The fault separates Devonian rock sequences to the west from younger Jurassic sediments
in the east. Laid down in a multiplicity of marginal marine and terrestrial environments, the
rocks exposed along the Brora and Helmsdale coast represent small fragments of the much
thicker sequences found in the North Sea. Consequently, they have enormous importance
in helping to understand the oil and gas-bearing rocks of the North Sea Basin. The Jurassic
sequences include classic sections illustrating the Kimmeridge Clay, with the Helmsdale
Boulder Beds including the ‘Fallen Stack’ of Portgower thought to represent fan-type
deposition along a submarine fault margin. The Brora Coal and Brora Brick Clay deposits
represent the only historically economically viable deposits of their type north of the
Highland Boundary Fault.
3
Palaeontology
In addition to gastropods and worms, the Cambrian–Ordovician sequences in the north and
east of the zone yield a rich and diverse fossil marine fauna including brachiopods,
cephalopods, trilobites, sponges and conodont animals. Being deposited on the northern
margin of the Iapetus Ocean, this fauna resembles that of the North American Province and
shows a marked contrast with that found in the rocks of similar age in England and Wales,
which were laid down on the south shore of the Iapetus.
Page 127
10 January, 2002
The Jurassic rocks along the coast, at the margins of the North Sea Basin around Helmsdale,
are richly fossiliferous. The sequences provide a variety of fossil assemblages representative
of a variety of marine environments that prevailed at the eastern edge of the Scottish
landmass between 205 and 145 million years ago. Ammonites, which are crucial in Jurassic
biostratigraphy, and belemnites are among the commoner fossils. Several type species of
mollusc have been found in the Callovian sequences of Brora, conferring international
significance upon the Jurassic geology of Zone 5.
Plant fossils within the sequences, derived from remains swept into the marine environment
from the land areas that correspond to the present-day Highlands, provide an insight into
the Jurassic terrestrial flora. As yet, no dinosaurian remains have been found, although there
is a possibility that they may be found in the future.
4
Geomorphology
The landscape of this zone is dominated by extensive peat-covered plateau surfaces, with a
number of distinctive isolated mountains and mountain massifs (inselbergs) of more resistant
rocks rising above these surfaces to the west and south (Morven and Maiden Pap –
conglomerates; Scaraben – quartzite; Ben Loyal – syenite). In central Sutherland and
Caithness, the degree of glacial erosion of the landscape decreases eastwards, accompanied
by a corresponding increase in drift cover that in lowland Caithness attains considerable
thicknesses, where it infills pre-existing valleys and depressions. Many of the glens show
strong structural controls where glacial erosion has exploited pre-existing valleys, as seen in
the NW–SE orientation of the drainage in the SW of the zone (e.g. Shin and Cassley) and in
the N–S orientation of drainage in the north of the zone.
Glacial erosion in the eastern part of the zone in Caithness appears to have been relatively
limited, confined to moulding and smoothing the landscape. Here there is a strong SE–NW
grain to the ice moulding, reflecting the former ice movement direction. The thick drift
cover is exposed in many coastal and stream sections. The till cover includes erratic
material (with shells) derived from offshore and transported towards the north-west by the
ice (e.g. Baile an t-Sratha). A site at Leavad is exceptional for the occurrence of a large
transported mass of Lower Cretaceous sandstone. These deposits are of significant interest
for interpreting the former pattern of ice movements of the last ice sheet from the Moray
Firth to the Atlantic and for interpreting the interactions of this ice with more locally
generated ice (e.g. Drumhollistan). The Caithness tills appear relatively weathered and have
been significantly modified by solifluction. This has led to claims that both they and the tills
of Orkney pre-date the Late Devensian glaciation, but this now appears unlikely from what
is known about the offshore extent of the last ice sheet.
The occurrence of clear moraines and glaciofluvial landforms is generally uncommon in this
zone. Hummocky drift occurs locally in central Caithness near Dirlot and deglacial
landforms are well developed in Strathnaver and Strath Halladale. Large outwash deltas
occur at Brora and Helmsdale. None of these deposits has been investigated in detail, but
they have significant research potential for linking the deglacial histories of the Moray Firth
and Wester Ross areas. Loch Lomond Readvance moraines are well developed in the
extreme west of the zone, e.g. in Glen Oykel, on the eastern flank of Ben More Assynt in
upper Glen Cassley, at the head of Strath More and on the eastern flanks of Ben Hope.
Page 128
10 January, 2002
On the mountains, periglacial features, notably solifluction terraces and wind and frostrelated patterns in the vegetation, are well developed on Morven and Ben Klibreck. Ben
Loyal is noted for its tors and weathering features.
There are a number of key pollen sites in the zone. Of notable importance are those that
relate to the vegetation history of the Flow Country and particularly the forest history.
Pollen studies from Loch of Winless and other sites suggest that the Flow Country to the
south and west was never extensively forested during the Holocene. However, pine
expanded briefly about 4000 14C yr BP, before retreating as the climate deteriorated. A key
site at Lochan an Druim, near Eriboll, provides a record of vegetation history during most of
the Late-glacial and Holocene for this extreme north-west part of Scotland. Birch and hazel
woodland developed, pine was locally present, but oak did not extend this far north.
The coastline of the Peatlands of Caithness and Sutherland adopts three distinctive and
contrasting forms, corresponding broadly to differences in the hardness and structure of the
underlying rock strata. Along much of the north-facing coast of this zone, Moine Schists and
other highly deformed metamorphic rocks outcrop. These tend to strike in a north–south
direction, thereby producing a highly crenulated coastline where wave erosion has picked
out less resistant beds or where streams and rivers have scoured valleys into the bedrock.
In many of the resulting coves and inlets, sand has collected to form beaches of stunning
beauty, such as Farr Bay and Melvich Bay, or systems of outstanding geomorphological
interest, as at Torrisdale Bay and Invernaver.
North east of Helmsdale, in the east, the coast is rugged and formed in granite and
Devonian sandstones. It is consequently dominated by cliffs and related landforms such as
stacks and geos. These cliffs may reach 120 m in height, and the variety of landforms is most
clearly demonstrated along the coast between Lybster and Ulbster.
South-west of Helmsdale the bedrock changes to softer Jurassic sediments, and
consequently the coastline adopts a lower, more subdued relief. Sand and shingle beaches
are much more common and suites of raised shore platforms and beaches are clearly
demonstrated, particularly around Lothbeg and Brora respectively. The renowned ‘fallen
stack of Port Gower’ is, rather disappointingly, misnamed, and originated long before the
present coastline was formed, as a result of slumping along a fault plane in the underlying
bedrock.
Caithness and Sutherland contain approximately 30,000 hectares of open water (Lindsay et
al., 1988), the majority residing in the maze of mires (locally known as flows), tiny pools,
lochans and lochs that give the area its name. The zone is generally low lying with the
majority of hills in the north-east being less than 300 m, and the associated gentle gradients
have been instrumental in peat formation. The north and west of the zone are more
mountainous with some short, relatively straight mountain torrents and upland waterfalls
draining these upland areas. River catchments in The Peatlands of Caithness and Sutherland
are larger than those in the North-West Seaboard, and many of the streams flowing on the
surface of the peat have dendritic drainage systems draining intermittently into lochs (which
helps determine the large catchment area). Subsurface drainage, through the glacial drift
beneath the peat, results in the formation of ‘sink holes’ and associated erosion complexes
within the bog. In areas where there is a high density of lochs and lochans, there are usually
fewer streams on the surface. In the central plain, a number of base-poor springs rise or
areas of seepage occur (e.g. Chalybeate Springs, ND 011346). These are due to the
Page 129
10 January, 2002
underlying deposits of granite, schists and drift. In addition, drainage has been undertaken on
significant proportions of the peat for agriculture and forestry (Lindsay et al., 1988). This
alters the water-table and changes the balance between sediment and water in the
catchment.
The major rivers located within the Peatlands of Caithness and Sutherland include the River
Helmsdale and the River Fleet, which drain south-east. The floodplain of the Helmsdale
below the Strath of Kildonan is restricted between two areas of higher land, limiting
channel pattern development. The Helmsdale has a gravel bed, and alluvial gold has been
found in the bed sediments. The River Brora also flows south-east, is divided and meanders
irregularly in the upper and middle reaches. Channel cut-offs (NC 726094) indicate that the
river is active. The River Shin drains Loch Shin and displays the characteristics of a
rejuvenated upland channel that is also divided in its upper reaches (NC 574005). In
contrast, the River Oykel meanders within a wider floodplain, but it also displays division
and former channels (NC 4501).
In addition to rivers draining south-east, the zone also contains the north-draining Rivers
Halladale, Naver, Borgie, Strathy and the Upper River Thurso, which all flow into the
Pentland Firth. The River Naver has a large upland catchment and is braided in the uppermiddle reaches before becoming irregularly meandering in the lower reaches, ending in a
sandy estuary. The River Strathy follows a similar pattern but has irregular meanders in the
lower reaches. Some of the headwaters of the Halladale River are deeply incised into glacial
materials, and the tight meander train is a function of the incision. In the lower reaches
there is evidence of division and meander bend cut-offs, which suggest that the river is
active here.
5
Soils
Soil development in most of the region has resulted in peat formation as a result of the
effects of climate, topography, drainage and parent materials. Low temperature, high rainfall
and poor subsurface drainage produce conditions where biological activity is reduced and
plant materials accumulate at the surface. Slow fermentation of organic matter results in
increased acidity, and this provides conditions for unique bog communities that are tolerant
of anaerobicity and acidity. The peat soil resource is important as a store for a very large
amount of terrestrial carbon, and it is one of the largest peatland areas in the world. Most
soils in the zone, if not peat, have peaty topsoils and this represents a large proportion of
organic matter stored in soils in the UK (71% of UK soil carbon is found in Scottish soils). A
total of 73% of the soils in this zone are either deep peat or shallow peat formed on
surface-water gleys. The Dubh Lochan peat soils are of international significance for their
size, extent and network of pools and unique erosion features at Knockfin Heights.
6
Summary of key Earth science features in the Peatlands of
Caithness and Sutherland
The principal Earth heritage interests in the Peatlands of Caithness and Sutherland are
summarised in Table 5.1. The Peatlands of Caithness and Sutherland includes a total of 29
GCR sites.
Page 130
10 January, 2002
Table 5.1
GCR sites in the Peatlands of Caithness and Sutherland
GCR block
No. of sites Principal interests
Moine
Cambrian
12
1
Caledonian Igneous
3
Non-marine Devonian
1
Kimmeridgian
1
Oxfordian
1
Bathonian
1
Callovian
1
Hettangian–Pliensbachian
1
Mesozoic Palaeobotany
Quaternary of Scotland
2
4
Coastal Geomorphology
1
7
Representative sections of the Moine Assemblage
Classic Cambrian to Ordovician sedimentary
sequences
Igneous rocks formed as a result of the Caledonian
Orogeny – some of which are of international
significance
Representative sites for Devonian palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Jurassic fossil plant flora
Representative sites for last ice-sheet deposits and
flow patterns
Complex juxtaposition of coastal, glacial and postglacial
landforms at Torrisdale Bay and Invernaver
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the Peatlands of Caithness and Sutherland are summarised in Table 5.2.
However, there is no systematic information on current impacts or trends.
Page 131
10 January, 2002
Table 5.2
Potential pressures and vulnerability of Earth heritage interests in the Peatlands of
Caithness and Sutherland
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments; land
management changes; construction of tracks; afforestation;
river management
Generally robust to all but large scale developments such as
superquarries
Vulnerable to mineral extraction from beaches; coast
protection; and sea level rise
Vulnerable to land management changes, pollution, drainage
Vulnerable to afforestation; land management changes, drainage
Vulnerable to enhanced erosion through overgrazing and
increased recreational pressures
Vulnerable to drainage of bogs and peat extraction
Palaeontological interests
Quaternary depositional landforms
and exposures
Rock coast features
Beach and dune landforms
Peat soils
Peatland hydrology
Periglacial geomorphology
Palaeoenvironmental records
8
•
•
•
•
•
•
•
•
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Fossils are collected from the fossiliferous exposures.
Peat erosion occurs with inappropriate land use.
Exposure of Quaternary sediments is variable and requires ongoing erosion to maintain
sections.
Possibility that drainage of peat may have affected the viability of some pollen records.
Impacts of forestry on peat hydrological systems.
Further erosion is a significant threat to peat deposits/soils across the area.
Impact of drainage on peat soils.
Commercial peat extraction may be a threat to some pollen sites.
Potential threats from climate change to periglacial process activity and soils on the
higher summits, both through direct changes in processes (frost, wind, water) and
through possible changes in vegetation.
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1996) Coasts And
Seas Of The United Kingdom. Region 3. North-east Scotland: Cape Wrath to St. Cyrus. Joint Nature
Conservation Committee, Peterborough.
Cleal, C.J., Thomas, B.A., Batten, D.J. and Collinson, M.E. (2001) Mesozoic and Tertiary Palaeobotany of
Great Britain. Geological Conservation Review Series, No. 22. Joint Nature Conservation Committee,
Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993). Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Page 132
10 January, 2002
Hambrey, M.J., Fairchild, I.J., Glover, B.W., Stewart, A.D., Treagus, J.E. and Winchester, J.A. (1991) The
Late Precambrian Geology of the Scottish Highlands and Islands. Geologists’ Association Guide, 44.
HR Wallingford (2000) Coastal Cells in Scotland. Cell 3 – Cairnbulg Point to Duncansby Head. Report to
Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and
Historic Scotland. SNH RSM Report No. 145. Battleby.
HR Wallingford (2000) Coastal Cells in Scotland. Cell 4 – Duncansby Head to Cape Wrath. Report to
Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and
Historic Scotland. SNH RSM Report No. 146. Battleby.
Johnstone, G.S. and Mykura, W. (1989) British Regional Geology: The Northern Highlands of Scotland (4th
edition). British Geological Survey. HMSO, London.
Lindsay, R.A., Charman, D.J., Everingham, F., O’Reilley, R.M., Palmer, M.A., Rowell, T.A. and Stroud,
D.A. (1988) The Flow Country. The Peatlands of Caithness and Sutherland. Nature Conservancy Council,
Peterborough.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Dept. of
Geography, University of Aberdeen. Countryside Commission for Scotland, Battleby, Perth.
May, V. and Hansom, J.D. (in press). Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Ritchie, W. and Mather, A.S. (1970) The Beaches of Caithness. Dept. of Geography, University of
Aberdeen. Countryside Commission for Scotland, Perth.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland, Methuen, London.
Smith, J.S. and Mather, A.S. (1973) The Beaches of East Sutherland and Easter Ross. Dept. of Geography,
University of Aberdeen. Countryside Commission for Scotland, Perth.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Wright, J.K. and Cox, B.M. (2001) British Upper Jurassic Stratigraphy (Oxfordian to Kimmeridgian) Geological
Conservation Review Series, No. 21. Joint Nature Conservation Committee, Peterborough.
10
Maps
British Geological Survey 1:50,000 maps: 102, 108, 109, 114, 115.
Soil Survey of Scotland Maps: 1:250,000 sheet 3 encompasses Zone 5 and coloured 1:63,360 sheets
115,116,109 and 110 cover most of The Peatlands of Caithness and Sutherland. MLURI, Aberdeen.
Page 133
10 January, 2002
ZONE 6
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
WESTERN SEABOARD
Highlights
The most geologically diverse area of Scotland.
Some of the southernmost exposures of Lewisian Gneiss.
Type locality of the Torridonian Sleat Group.
Sedimentary features preserved in the Moine.
Cambrian and Ordovician rocks with a fossil fauna of North American affinities.
Distortion of the Great Glen Fault around the Mull volcanic centre.
The furthest north exposure in northwest Europe of Upper Carboniferous sedimentary
rocks.
Lower, Middle and Upper Jurassic sedimentary sequences.
The location of Scotland’s first unequivocal dinosaur finds.
Some of the oldest known mammal remains.
Rare Upper Cretaceous sedimentary sequences.
Interbasaltic sedimentary sequences yielding a internationally significant flora and fauna.
Four major Tertiary volcanic centres, of major international significance in the study of
volcanic and magmatic processes.
Classic localities for glacial and periglacial landforms, including landforms of mountain
glacier erosion, a trim line of the last ice sheet and Loch Lomond Readvance mountain
glacier landforms.
Unique large-scale mass movements, partly glacially modified.
Key reference sites for Late-glacial and Holocene palaeoenvironmental change, including
forest history and human impacts on the landscape.
Classic localities for raised shore platforms and relict cliff forms.
The most extensive occurrence in Scotland of coastal landslips and coastal waterfalls.
Finest example in Scotland of columnar basalt topography, on Staffa.
Brown earth soils developed on windblown material, Trotternish, Skye.
Geology
Dominated by the remains of four 60-million-year-old volcanoes, the Western Seabord
zone encompasses the most geologically diverse area of Scotland. A huge variety of
sedimentary, igneous and metamorphic rocks are present, and all but two of the geological
periods dating back to the Cambrian, 590 million years ago, are represented by the rocks
within the zone.
Lewisian Gneisses, outcropping on Rona, Raasay, Skye and Iona, are the oldest rocks within
the zone and form the crustal foundations upon which the younger rocks rest and intrude.
Named after the Isle of Lewis, the Lewisian Gneisses are among some of the oldest rocks in
northwest Europe. Much of the Lewisian Gneiss dates back to the Archaean, a period in
Earth history that ended around 2500 million years ago. The Lewisian Gneiss formed as the
result of several major tectonic events which repeatedly metamorphosed and deformed
what were originally ancient volcanic and sedimentary rocks. Such was the intensity of
metamorphism that nothing remains of their original sedimentary and volcanic structure, or
the microscopic fossil life present in the Archaean; geochemistry is the only tool to
elucidate the original rock character.
Page 134
10 January, 2002
Around 1500 million years ago, the Lewisian Gneiss represented the bedrock of the southeastern edge of a continental landmass called Laurentia. Laurentia incorporated the
Northwest Highlands of Scotland and much of what is now Greenland and North America.
Erosion of the Lewisian bedrock making up the Laurentian landmass gave rise to vast
quantities of sand and other sediment, which was washed southward across the area that
now represents the Northwest Highlands. Current understanding is that deposition of the
sediment took place over hundreds of millions of years, giving rise to vast sedimentary
sequences known as the Moine Assemblage and the Torridonian Sandstone.
Named after the peninsula of a’Mhoine in northern Sutherland, the Moine Assemblage make
up much of Northern Scotland. Within the Western Seaboard zone, Moine rocks are found
on the south-west coast of Mull and on Ardnamurchan. On the mainland, the Moine
Assemblage is composed of three distinct divisions: the Morar Division, the Glenfinnan
Division and the Loch Eil Division. The precise relationship between the three divisions is
still being debated, although it is generally agreed that the Morar and Loch Eil Divisions are
the oldest and the youngest respectively. However, at Ardalanish Bay on Mull there is an
important sequence that demonstrates rocks of the Glenfinnan Division resting upon rocks
of the Morar Group.
The sediment comprising the Moine Assemblage is thought to have accumulated over
several hundred million years, between 1500 million and1050 million years ago, to form a
pile several kilometres in thickness upon the ancient Lewisian Gneiss; the Loch Morar
Division itself reaches in excess of 6 km. After the deposition of the sediment pile, the
collision of continental landmasses, through the mechanism of plate tectonics, deformed and
metmorphosed the sediments. The metamorphic and deformational history of the Moine
Assemblage was complex and there were several phases of mountain building, or orogeny,
resulting from continental collision, starting around 1000 million years ago. The various
sedimentary rocks were metamorphosed to schists and gneisses, with the recrystalisation of
sandstones to quartzites and the more muddy sediments to pelites. The metamorphism was
not entirely uniform, with the result that some portions of the Assemblage were subjected
to high-grade metamorphism, resulting in the formation of gneisses, whereas other areas
escaped relatively unscathed with the preservation of the features characteristic of the
original sedimentary rock, such as layering and dune-bedding. Well preserved sedimentary
structures within outcrops of the Morar Division can be observed at Gribun on Mull and
along the southern coast of Ardnamurchan.
On Skye, Rona, Scalpy, Rum and possibly Iona, there occur the remnants of the other great
Precambrian sedimentary sequence, the Torridonian Sandstone. The Torridonian within the
Western Seaboard zone is subdivided into two distinct groups, the older Sleat Group
(named after the Sleat peninsula on Skye) and the younger Torridon Group. Deposited
around 800–700 million years ago, the Sleat and Torridon Groups represent sediment
deposited in rift valleys that developed on the Laurentian continental margin. The
lowermost Torridonian sediments rest upon and infill an ancient landscape that had been
eroded into the old Lewisian Gneisses, a good example occurring at the north end of Iona.
The lack of subsequent metamorphism of the sediments has meant that all of the original
features of the sediments, including layering, dune-bedding, mudcracks, rain prints and some
microscopic fossils (found on the mainland), are often perfectly preserved, revealing a lot of
information concerning the precise environmental conditions in which the sediment was laid
down. The vast thickness of the Torridonian sequence, which amounts to several
Page 135
10 January, 2002
kilometres, can be appreciated at Loch Scresort on eastern Rum, where a section through a
couple of kilometres of gently dipping strata can be observed.
Although originating as loose sediment on the south-eastern margin of the Laurentian
continent, the Torridonian is younger than the Moine, and in contrast to the Moine rocks is
relatively undeformed, having not been subjected to successive metamorphic events.
Formerly thought to have formed contemporaneously with the Moine, the precise
relationship between the Moine and the Torridonian is still poorly understood.
A tiny but significant sequence of rocks belonging to the Dalradian Supergroup occurs at
Loch Don on Mull. The Dalradian rocks, which extend into neighbouring Zones 13 and 14
and further afield into Zones 9, 10, 11, 12, 15 and 21, are predominantly quartz-, feldsparand mica-rich, representing a metamorphosed and structurally deformed pile of marine
sediments and volcanic rocks, with a total thickness of around 25 km evident on the
mainland. Underlying more of the Scottish landscape than any other group of rocks, the
Dalradian is thought to be the younger continuation of the Moine Supergroup, although it is
currently thought to be almost entirely of Precambrian age. The Loch Don Dalradian on
Mull consists of grey slates and limestones.
Although the Torridonian and underlying Lewisian were not subjected to metamorphism in
the 200 million years before the start of the Cambrian Period, the area was subjected to a
period of folding. Considerable erosion followed the folding, and several hundred metres of
Torridonian rocks were removed in places to lay bare the underlying Lewisian Gneiss. By
the beginning of the Cambrian, erosion (possibly marine) had produced a remarkably flat
surface, passing across hard gneiss and sandstone alike. Cambrian sediments were deposited
on this surface as it progressively and gently subsided to form the floor of a shallow shelf
sea. This shelf lay on the south-east side of the Laurentia continental landmass, which
bounded the Iapetus Ocean on its north-west side.
The remains of the Cambrian and Ordovician age sediments laid down in this shallow sea
now occupy an area between Broadford and Loch Slapin, and to the south of Loch Eishort
on Skye. This sedimentary rock pile consists of a lower suite of rocks comprising
sandstones, siltstones and mudstones and an upper carbonate, or limestone, sequence. A
probable maximum thickness for the whole sequence on Skye amounts to around 500 m.
The sandstones at the base of the Cambrian sequence, which include the famous Pipe-Rock,
are interpreted as having formed in shallow tidally influenced marine conditions; the ‘pipes’
representing the burrows of worms. The carbonate-rich siltstones and shales of the
overlying Fucoid Beds record a lagoonal environment superimposed upon the tidal
sandstones below. The Salterella Grit at the top of this lower suite comprises sandstone.
Filled with the remains of fossil gastropod shells, the Salterella Grit is thought to have
formed a linear sand body in the marine environment. The upper carbonate, or limestone,
sequence forms the bulk of the Cambrian–Ordovician sequence, and is made up of the
seven formations of the Durness Limestone. Formed in tidal flat and shallow marine
conditions, the limestone was derived largely through chemical precipitation of carbonate
from the sea water. The junction between the Cambrian and Ordovician systems lies within
the Durness Limestone.
By the Silurian period the once great Iapetus Ocean was closing, bringing together the two
continental landmasses on either side. This closure brought about an event known as the
Page 136
10 January, 2002
Caledonian Orogeny, which metamorphosed and deformed the Dalradian Supergroup and
the underlying rock, on the continental margins of the Iapetus. Although almost all of the
area that is now Scotland was affected, the rocks within Zone 6 lay outwith the area that
experienced the most intense metamorphism and deformation. However, the zone does
contain one of the most famous geological structures of the Caledonian Orogeny, the Moine
Thrust. Thought to extend for over 500 km, the Moine Thrust was formed late in the
orogeny, around 430 million years ago. Within the zone, the thrust can be traced southeastwards across the Sleat peninsula, from where it is thought to run eastward of Rum and
Eigg toward the Sound of Iona and beyond.
The Moine Thrust formed as compressive forces, directed upwards and outwards from the
point of continental collision, pushed previously metamorphosed Moine rock northwestwards over the Cambrian–Ordovician sedimentary sequence and Lewisian Gneiss. The
Moine Thrust is the most important single thrust fault in a zone of low-angle thrust faults
that make up the Moine Thrust Zone. It is thought that the Moine rocks moved around 70
km over the rocks to the west along these low-angle thrusts. Movement along the thrust
planes produced a localised highly deformed rock type known as mylonite. Within the
Moine Thrust Zone in the vicinity of Loch Slapin, masses of Torridonian Sandstone were
thrust, or carried over, the Cambrian and Ordovician sequence.
Another feature of the Caledonian Orogeny, and of this zone, is the Great Glen Fault, which
occurs on south-east Mull. This major fault in Scotland’s crust represents the point where
two blocks of crust, which form Scotland’s foundations, slid past one another. The lateral
displacement of the crust on either side of the fault is major and amounts to many tens of
kilometres, but the fault is no longer interpreted as a terrane boundary like the Iapetus
Suture, which represents the ‘join’ in the crust between Scotland and England, described in
the prospectus for Zone 20. The fault has been reactivated during subsequent periods of
Earth movements and still active today.
At the end of the Caledonian Orogeny, partial melting of rocks within the crust, following
the deformation and metamorphism, resulted in the formation of great masses of silica-rich
melt that moved upward through the crust. The roughly circular Ross of Mull Granite, a
prime example of a pluton, was emplaced around 410 million years ago.
During the Devonian Period, following the Caledonian Orogeny, huge amounts of sediment,
which had been derived through the erosion of the new mountain chain, were deposited in
the Midland Valley area and the Moray Firth. Although there is no evidence of Devonian
sediments within Zone 6, there is nothing to suggest that sediment deposition did not take
place at this time. There is, however, a patch of Devonian age lavas and ashes in the vicinity
of Loch Don on Mull. These volcanic rocks represent part of the Lorne Plateau Lavas that
dominate the geology in the vicinity of Oban and which erupted around 400 million years
ago.
On the Sound of Mull, at Inninmore Bay, a patch of Upper Carboniferous rocks was laid
down as sand and muds 309 million years ago. Rocks of this type are quite widespread in
the Midland Valley of Scotland and elsewhere in the UK, but these are the most northerly of
their age in northwest Europe and the only known Upper Carboniferous rocks north of the
Great Glen Fault line. The deposits were laid down in delta-like environmental conditions
that prevailed within a relatively low-lying area in the mountain landscape of the Morvern
area.
Page 137
10 January, 2002
The Carboniferous rocks at Inninmore Bay are overlain by 220-million-year-old Triassic
rocks. During Permian and Triassic times an arid climate prevailed across what is now
Scotland, and red sandstones and conglomerates were deposited on alluvial fans and in the
low-lying plains away from the high ground. The sediment would have been carried across
the fans and out onto the plains by ephemeral rivers. Raasay, the Strath on Skye, Rum,
Ardnamurchan and Mull all yield exposures of Triassic rock, the greatest thickness of
exposure occurring on Mull.
Around 205 million years ago, at the start of the Jurassic period, the area now encompassed
by Zone 6 was submerged beneath a shallow tropical sea. Sediment deposition occurred
intermittently throughout the area over the next 70 million years, with a period of
shallowing during the Middle Jurassic, resulting in deltaic conditions persisting over the
northern part of the zone for several million years. Lower, Middle and Upper Jurassic rocks
are found throughout the zone, but nowhere is the 1000-m sequence exposed in its
entirety. Hallaig on Raasay, Trotternish and Elgol on Skye, Kildonnan on Eigg and Carsaig on
Mull yield the principal Jurassic sequences, with additional exposures on Scalpay and
Ardnamurchan. Shales and limestones dominate the lower Jurassic; sandstones and shales
predominate in the Middle and Upper Jurassic, respectively. Important rock sequences of
the Hebrides Jurassic include the Broadford Beds, the Scalpa Sandstone, the Raasay
Ironstone and the Great Estuarine Group, the last one encompassing Hugh Miller’s Reptile
Bed.
After the Jurassic, at the start of the Cretaceous Period around 135 million years ago, sea
levels dropped relative to the land, and erosion of the newly deposited sediments took
place. By late Cretaceous times, around 95 million years ago, the area was once again
submerged beneath the sea and there was widespread sediment deposition across what is
now Britain. Only a few of the highest areas were left above sea level. In the Hebrides area
calcareous sandstones were deposited, followed by a thin layer of chalk. Although nowhere
thicker than 4 m, the chalk is directly analogous to the huge thicknesses outcropping on the
Antrim Coast and the south coast of England. Not much remains of what was once an
extensive cover of Cretaceous sediment within the zone, but there are notable sequences
at Lochaline, at Loch Don, Gribun and Carsaig on Mull, on Eigg and on Raasay. The
thickness and purity of the Cretaceous White Sandstone at Lochaline has led to its mining
for use in glass-making.
At the end of the Cretaceous Period, the area was lifted above sea level and subjected to
erosion. Above the Cretaceous sequences on Morvern and in Mull, a thin, brown layer of
clay, from the early Tertiary Period, represents altered volcanic ash which marks the onset
of the last phase of volcanic activity in Britain. This activity, which lasted for around 12
million years, was associated with the split of northern Europe from Greenland and North
America, with the formation of the northern North Atlantic. This volcanic activity within the
zone therefore represents part of a much larger area of activity that extends along the
eastern seaboard of Greenland, the western margin of the Rockall Plateau, through the
Faeroes and Iceland. Volcanic ash was the first surface product of the activity, ahead of huge
outpourings of lava that piled up to a maximum thickness of 3000 m. The lavas were
principally fed from fissures similar to those in present-day Iceland. The lavas, which were of
basaltic composition, covered the eroded land surface of Precambrian to Cretaceous age
rocks. Occasionally, the lavas covered landscapes of considerable relief, filling valleys,
burying hills and sometimes flowing into shallow lakes. During quiescent periods, the lava
landscape was subjected to intense weathering with the formation of bright-red laterite
Page 138
10 January, 2002
deposits, akin to soils found above basaltic rock in tropical areas of the world today. The
remains of vegetation that thrived between periods of volcanic activity occur within the lava
sequences, e.g. at Ardtun on Mull. The plateau basalts at outcrop level underlie more of the
zone than any other rock type. In western Mull, the erosion of the lava plateau has created
the stepped topography of the Burg.
After the fissure eruption style of volcanism, activity became centred at regular points along
what was to become western Scotland. Within the zone, the areas that now correspond to
Skye, Rum, Ardnamurchan and Mull were the sites of large volcanoes. Supplied from magma
chambers within the crust, the volcanoes erupted intermittently over a few million years,
approximately 60–56 million years ago. A variety of igneous rock types including granite,
gabbro and peridotite were associated with the igneous complexes. The gabbros and
peridotites are basic and ultrabasic rocks, respectively, and were derived from partial
melting of the upper mantle. The more ‘evolved’ acid igneous rocks, which are silica rich
(such as granite), were derived either through differentiation of the basic rocks, or through
partial melting of other rocks in the crust such as Lewisian Gneiss and Torridonian
Sandstone. The development of the volcanic centre had the effect of distorting the NE–SW
lineament of the Great Glen Fault
The various igneous rocks have responded in different ways to the profound erosion of the
last 50 million years. Gabbro and peridotite have given rise to the rugged mountain scenery
of the Skye Cuillin and Rum; the considerable, but generally less-rugged Red Hills of Skye
are composed of granite; and the piles of flat-lying lavas have formed tabular, ‘trap-featured’
hills in northern Skye, rising sometimes to form high mountains, such as Ben More on Mull.
3
Palaeontology
In addition to gastropods and worms, the Cambrian–Ordovician sequences in the north of
the zone, on Skye, yields a rich and diverse fossil marine fauna including brachiopods,
cephalopods, trilobites, sponges and conodont animals. Being deposited on the northern
margin of the Iapetus Ocean, this fauna resembles that of the North American Province and
shows a marked contrast with that found in the rocks of similar age in England and Wales,
which were laid down on the south shore of the Iapetus.
The Carboniferous sediments at Inninmore Bay yield the fossil remains of plants that grew
in and around a low-lying area of the Caledonian Mountains, centred on Morvern. To date
no animal fossils have been found in the sequence.
All of the Jurassic system, Lower, Middle and Upper, is represented by the relatively small
outcrops of Jurassic rocks that are scattered throughout the Inner Hebrides. Skye and
Rassay have the major areas of outcrop, with Mull, Eigg and Ardnamurchan yielding
subsidiary exposure. A rich diversity of marine fossils, representing a variety of marine
ecosystems, occurs throughout the Jurassic sequences. Ammonites, which are fundamental
in Jurassic biostratigraphy, are fairly ubiquitous, particularly in the Lower and Upper Jurassic
sequences, where marine conditions prevailed. Non-marine deposited strata of the Middle
Jurassic have yielded Scotland’s first true dinosaurian remains and tracks, with bones
ascribed to both sauropods and therapods having been recently discovered. Some of the
oldest recorded mammal remains in the world occur within the Jurassic deposits of Skye.
Page 139
10 January, 2002
The remains of substantial marine reptiles have been found in Hugh Miller’s Reptile Bed on
Eigg.
Rare exposures of Cretaceous rocks within land-slipped areas in Western Mull, and in situ in
Morvern, provide the fossil remains of shelly marine faunas that lived when world sea levels
reached their highest level ever in Late Cretaceous times.
Inter-basaltic sediments, laid down in quiescent periods during the outburst of volcanic
activity at the start of the Tertiary Period, yield the fossil remains of a rich and diverse flora.
The fossil flora, at Ardtun on Mull, for example, is indicative of sub-tropical environmental
conditions and occurs in association with fossil invertebrates including beetles. To date, no
fossil representatives of a ‘mega-fauna’ have been found, although this may change with
future research and excavation. One of the more spectacular fossils finds to date is
McCulloch’s Tree at Ardmeanach, western Mull, which represents a trunk, possibly in
growth position, that was engulfed by molten lava.
4
Geomorphology
The geomorphology of the region relates closely to the underlying geology. The upstanding,
former volcanic centres of Skye and Rum formed focal points for the development of
mountain glaciers and icefields and today illustrate excellent examples of mountain glacier
landforms. The Cuillin, in particular, contain the most ‘alpine’ type of scenery in Britain, with
a superb assemblage of corries, arêtes, troughs, rock basins and ice-moulded bedrock. The
older, lower rocks (Torridonian, Moine) on southern Skye, Ardnamurchan and northern
Rum are generally extensively ice scoured. A trimline marking the upper limit of the last ice
sheet is developed along the Trotternish Peninsula. Glacial deposits are well represented,
particularly in association with the Loch Lomond Readvance. The corries of the Cuillin have
excellent examples of lateral and end moraines, and there are extensive fields of
‘hummocky’ moraine near Sligachan on Skye and in Glen More on Mull. In SE Skye there are
moraines that may represent an earlier ice advance. Fluvioglacial deposits are relatively rare,
the exception being the large delta terraces near Kyleakin on Skye.
Vegetation history has been studied at a number of sites, particularly on Skye and Mull.
Throughout the Lateglacial Interstadial, the vegetation of the islands was essentially treeless,
although some tree birch may have occurred locally on the southern islands. After the
vegetation revertance of the Loch Lomond Stadial, Holocene vegetation succession followed
a pattern from tundra heath to hazel–birch woodland. Subsequent vegetation development
reflected the diversity of habitats and climatic conditions. During the middle Holocene,
birch–hazel–alder woodland, with some oak, elm, ash, rowan and holly, was present in
southern Skye (Sleat), pine was present just to the north, but only birch, hazel and willow
scrub occurred in northern Skye. In areas to the south, birch–hazel scrub or woodland with
some oak and elm occurred. After about 4000 14C yr BP, woodland contracted and heath
and grassland expanded, probably in response to a combination of climate change and
human disturbance.
The Tertiary lavas give rise to distinctive scarp landscapes on Skye, Mull and Eigg. Where
these are underlain by weaker sediments, spectacular large-scale landsliding has occurred, as
at Trotternish, at Hallaig on Raasay and at Gribun. Parts of the slides, which are unique in
Britain, have been glacially modified.
Page 140
10 January, 2002
Periglacial features are locally well developed, as on the Western Hills of Rum, and there is
a long record of episodic Holocene slope activity and erosion at Trotternish where buried
soils occur.
The coastlines of the Ardnamurchan Peninsula and the various islands which make up this
zone are, in general, remarkably similar in character, reflecting broad similarities in their
underlying lithology and glacial and postglacial history. For the most part, the coastlines are
dominated by cliffs with only localised beach development. These cliffs are, however, largely
inactive today – i.e. they are unaffected by marine erosion at present times, having
originated during glacial or even pre-glacial times. Even then, faulting and glacial erosion
might have been more important in determining cliff form than marine processes. The
coastline is thus, in effect, inherited from these earlier times. Particularly fine cliffs are
evident at Waterstein on Skye, Carsaig on Mull and around much of the south and west
coasts of Rum.
Throughout the area traces of up to three separate raised beaches and shore platforms are
preserved. Nowhere are the platforms more clearly seen than on the Treshnish Islands,
where the High Rock Platform and the Main Rock Platform are exceptionally prominent.
The Main Rock Platform is also well displayed along the northeast coast of Mull. A
characteristic feature of the cliffs in this zone is the existence of coastal landslips and
waterfalls; indeed these are more abundant and clearly expressed here than anywhere else
in the UK. Superb examples of the former exist along the eastern coast of the Trotternish
Peninsula on Skye, and of the latter, at Bearraraig Bay on the same island.
The highly indented character of the coastline, the proximity of the mainland and the
sheltering effect of the Outer Hebrides all combine to reduce wave exposure on most
shores and so evidence of recent or contemporary marine erosion is sparse. Even Fingal’s
Cave on Staffa might have been formed largely during Late-glacial times. For similar reasons,
and because of frequently steeply sloping near-shore shelves, beach–dune complexes are
rare in this zone, the main exceptions being on the relatively more exposed shores of the
Ross of Mull and Iona, where, in addition, an extensive machair plain has also developed.
The irregular, indented coastline and fiord-like lochs mean that no part of Skye is more than
5 miles from the sea. This can inhibit the downstream development of river channel
planform. Many of the rivers in the Trotternish and Dunvegan peninsulas have coastal
waterfalls or waterfalls in their middle reaches, both of which are indicative of channel
response to relative changes in sea level. The River Snizort, a major river of northern Skye,
has well-developed downstream planform changes. At the inflow into Loch Snizort Beag, it
is sinuous but generally it meanders in its lower reaches (as do the Hamara River and
Osdale River) but braiding upstream in the middle reaches. Meanders in the upper reaches
of the main river and in the tributaries suggest that these reaches pass through low gradient
alluvial basins. The Snizort has recently been subject to damaging river engineering in its
lower reaches. In contrast, the floodplain of the Varragill River is constrained by slopes of
Stroc-bheinn in the lower reaches. This has led to the development of a rare, relatively long,
straight reach. The River Brittle, in southern Skye, meanders irregularly for much of its
length, and the River Sligachan shows some evidence of braiding in the middle reaches.
Southern Skye has more upland lochs and lochans than the northern part.
The small inner Hebridean Islands of Eigg, Muck, Rum and Canna have, by virtue of their
size, no major river systems on them. Indeed, Muck has virtually no evident surface-water
Page 141
10 January, 2002
drainage. The burns of Eigg flow east and west from a north–south watershed and, like Skye,
have a number of waterfalls in the upper or middle reaches. The burns of Canna drain to
the north and south. Two of the burns have right-angled bends in their upper reaches that
may be geologically related. Rum has a relatively dense network of rivers and lochans. Some
of the burns draining to the north-west end in coastal waterfalls. The main rivers, the
Kilmory River, the Kinloch River and Abhainn Rangail in Glen Harris, all meander to some
extent, although their floodplains are relatively narrow. The straight course of the Kilmory
river and Long Loch is due to their exploiting a geological fault. The flow of Kinloch River
was augmented by early engineering that reduced the flow in the Kilmory River.
A number of streams and burns drain north-west to the northern coast of Mull. In contrast,
the meandering River Tobermory drains east, suggesting that its headwaters were subject to
capture. Other major rivers on Mull include the River Aros and the River Bellart, but these
rivers do not display significant downstream change and many of their tributaries display
dendritic drainage systems. In contrast, the short River Bà runs parallel to the coast across
an extremely flat coastal plain. This is very unusual in a Scottish context. East Mull has two
major rivers (the Lussa and the meandering Forsa), a large number of tributaries and small
lochs and lochans.
The rivers of Ardnamurchan are short and steep and drain to the north and south from a
central east–west aligned watershed. There are some lochs and lochans evident there. The
western part of the Morvern peninsula also has short, steep rivers with a better developed
tributary network which displays a dendritic channel pattern in the headwaters. The extent
of standing water is more limited on Morven than on Ardnamurchan.
5
Soils
This area is characterised by diverse geology with a strong climate control, giving rise to
diverse soil associations. The important agricultural land is found on base-rich parent
materials, mainly brown forest soils and brown rankers on Tertiary basalts, Mesozoic
sediments and Cambro-Ordovician limestones. On Skye, brown forest soils are developed
on basalts up to 100 m asl, whereas further south, in Mull, the same soils are developed on
basalts up to 200 m asl. The more acid rocks on Skye (granite and Torridonian sandstones)
give peaty podzols characterised by various moorland plant communities. The gabbros,
basalts and sediments give nutrient-rich, forest-brown soils (but note that the summits have
no soil cover), and the Torridonian sandstones give nutrient-poor acid soils. The region has
a much higher frequency of brown earths than other zones in the north and west of the
country, which reflects the varied solid and drift geology. This means that the soils are
potentially more fertile and nutrient rich, but climatic and topographic constraints reduce
potential agricultural productivity. Most of Mull is dominated by plateau basalts, but the
south-east corner and major hills are of intrusive rocks representing the remnants of a
volcano (gabbro to granite). Brown forest soils are developed on the basalts up to 200 m asl
(contrast Skye, above) and the Mesozoic sediments. The hills of the Ross of Mull are
underlain by the Ross of Mull granite, and Iona is made up of Lewisian Gneiss. The soils here
are nutrient poor and acidic, reflecting the low base status of the drift and solid geology that
constitute the parent materials. The majority of soils in this zone are peaty gleys (64%) as a
result of impeded drainage and climatic conditions. Brown earths are confined to sites with
basic parent materials and are the most agriculturally valuable soils; those developed from
windblown material on Trotternish are nationally significant. Peat and peaty soils are locally
Page 142
10 January, 2002
significant as a source of fuel. Skye has a number of nationally significant or unique soils such
as the brown podzolic soils of the Sleat peninsula and the brown earths of Trotternish. The
main threat to the soils resource is from erosion such as on the steep slopes of Trotternish
ridge.
6
Summary of key Earth science features in the Western
Seaboard
The principal Earth heritage interests in the Western Seaboard are summarised in Table 6.1.
The Western Seaboard includes a total of 90 GCR sites.
Table 6.1
GCR sites in the Western Seaboard
GCR block
No. of sites
Principal interests
Torridonian
1
Moine
Caledonian Igneous
5
2
Tertiary Igneous
Cambrian and Tremadoc
38
1
Permo-Trias
1
Alenacian–Bajocian
2
Bathonian
5
Callovian
2
Cenomanian–Maastrichtian
1
Hettangian–Pliensbachian
6
Oxfordian
2
Toarcian
1
Westphalian
1
Jurassic–Cretaceous Reptilia
Palaeobotany
Palaeoentomology
Vertebrate Palaeontology
Mineralogy
Quaternary of Scotland
1
1
1
1
4
7
Mass Movement
3
Representative sites for Torridonian
palaeoenvironment and studies
Representative sections of the Moine Assemblage
Igneous rocks formed as a result of the Caledonian
Orogeny
Representative sites for Tertiary Igneous geology
Representative sites for Cambrian and Ordovician
palaeoenvironment and palaeoecological studies
Representative sites for Triassic palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Cretaceous
palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Jurassic palaeoenvironment
and palaeoecological studies
Representative sites for Carboniferous
palaeoenvironment and palaeoecological studies
Fossil remains of Jurassic dinosaurs
Fossil remains of Jurassic plants
Fossil remains of Tertiary insects
Fossil remains of early mammals
The occurrence of rare and unusual minerals
Classic glacial and periglacial landforms, and key
reference sites for Lateglacial and Holocene
vegetation history and environmental change
Large-scale landsliding
Page 143
10 January, 2002
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the Western Seaboard are summarised in Table 6.2. However, there is no
systematic information on current impacts or trends.
Table 6.2
Potential pressures and vulnerability of Earth heritage interests in the Western Seaboard
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction and infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; river management
Vulnerable to mineral extraction/quarrying; commercial
and industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Generally robust to all but large scale developments such
as superquarries
Generally robust to all but large scale developments such
as superquarries
Vulnerable to land management changes, pollution
Vulnerable to enhanced erosion through overgrazing and
increased recreational pressures
Vulnerable to drainage of bogs and peat extraction
Palaeontological interests
Quaternary depositional landforms
and exposures
Records of sea level change
Rock coast features
Mass movement features
Soils
Periglacial geomorphology
Palaeoenvironmental records
8
•
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Fossils are collected from the fossiliferous exposures. Dinosaurian remains on Skye have
been damaged by collectors as have the Ardtun Leaf Beds on Mull.
Erosion is a significant threat to peat deposits/soils across the area.
Bibliography
Ballantyne, C.K. (1990) The Late Quaternary glacial history of the Trotternish Escarpment, Isle of Skye,
Scotland, and its implications for ice-sheet reconstruction. Proceedings of the Geologists’ Association,
101, 171–186.
Ballantyne, C.K. (1991) The landslides of Trotternish, Isle of Skye. Scottish Geographical Magazine, 107,
130–135.
Ballantyne, C.K. (1998) Aeolian deposits on a Scottish mountain summit: characteristics, provenance,
history and significance. Earth Surface Processes and Landforms, 23, 625–641.
Ballantyne, C.K., Benn, D.I., Lowe, J.J. and Walker, M.J.C. (1991) The Quaternary of the Isle of Skye: Field
Guide. Quaternary Research Association, Cambridge.
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Region 14. South-west Scotland: Ballantrae to Mull. Joint Nature
Conservation Committee, Peterborough
Page 144
10 January, 2002
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Regions 15 and 16. North-west Scotland: The Western Isles and West
Highland. Joint Nature Conservation Committee, Peterborough.
Cleal, C.J. and Thomas, B.A. (1996) British Upper Carboniferous Stratigraphy. Geological Conservation
Review Series No. 11. Joint Nature Conservation Committee, Peterborough.
Cleal, C.J., Thomas, B.A., Batten, D.J. and Collinson, M.E. (2001) Mesozoic and Tertiary Palaeobotany of
Great Britain. Geological Conservation Review Series, No. 22. Joint Nature Conservation Committee,
Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Emeleus, C.H. and Gyopari, M.C. (1992) British Tertiary Volcanic Province. Geological Conservation
Review Series No. 4. Joint Nature Conservation Committee, Peterborough.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Hambrey, M.J., Fairchild, I.J., Glover, B.W., Stewart, A.D., Treagus, J.E. and Winchester, J.A. (1991) The
Late Precambrian Geology of the Scottish Highlands and Islands. Geologists’ Association Guide, 44.
Hinchliffe, S. (1999) Timing and significance of talus slope reworking, Trotternish, Skye, northwest
Scotland. The Holocene, 9, 483–494.
HR Wallingford (2000) Coastal Cells in Scotland. Cell 5 – Cape Wrath to the Mull of Kintyre. Report to
Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and
Historic Scotland. Scottish Natural Heritage Research, Survey and Monitoring Report, No. 147.
Battleby.
Mather, A.S. and Crofts, R. (1971) The Beaches of West Inverness-shire and North Argyll. Dept. of
Geography, University of Aberdeen. Countryside Commission for Scotland, Perth.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Dept. of
Geography, University of Aberdeen. Countryside Commission for Scotland, Battleby, Perth.
Mather, A.S., Smith, J.S. and Ritchie, W. (1974) The Beaches of Northern Inner Hebrides. Dept. of
Geography, University of Aberdeen. Countryside Commission for Scotland, Perth.
May, V. and Hansom, J.D. (in press). Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Richey, J.E. (1961) British Regional Geology, Scotland: the Tertiary Volcanic Districts. 3rd edition, revised by
A.G. MacGregor and F.W. Anderson, HMSO, Edinburgh.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Selby, K.A. (1997) Late Devensian and Holocene relative sea-level changes on the Isle of Skye, Scotland.
Unpublished PhD thesis, University of Coventry.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland, Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Walker, M.J.C., Gray, J.M. and Lowe, J.J. (1985) Island of Mull. Field Guide. Quaternary Research
Association, Cambridge.
Wright, J.K. and Cox, B.M. (2001) British Upper Jurassic Stratigraphy (Oxfordian to Kimmeridgian) Geological
Conservation Review Series, No. 21. Joint Nature Conservation Committee, Peterborough.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 43, 44, 51, 52, 60, 70, 71, 80, 81, 90
Soil Survey of Scotland Maps: 1:250,000 sheet 4 encompasses Zone 6 and uncoloured 1:50,000 sheets
23,32,33,39,40,46 and 49 cover the islands and coastal areas. MLURI, Aberdeen.
Page 145
10 January, 2002
ZONE 7
1
•
•
•
•
•
•
•
•
•
•
•
2
NORTHERN HIGHLANDS
Highlights
The most extensive area of Moine Assemblage rocks in Scotland.
Zoisite mineralisation in marble.
The occurrence of the Great Glen Fault, one of Scotland’s most distinctive fault lines.
Internationally significant Devonian fossil fish remains.
Landscapes of glacial erosion, notable for watershed breaching.
Outstanding examples of landforms and sediments associated with ice-dammed lakes.
Representative examples of Loch Lomond Readvance mountain glacier landforms.
Large rock slope failures developed on schist.
Excellent representative periglacial landforms developed on schist, including relict and
active features.
Excellent examples of river meander landforms and processes in an upland environment.
Excellent example of geomorphological effects of raising base level, at Loch Ness.
Geology
The Northern Highlands zone encompasses three distinct groups of rocks that span over a
billion years of Earth history. The oldest rocks in the zone are of Lewisian Gneiss, which
outcrop around Loch Monar and in the vicinity of Scardroy. Named after the Isle of Lewis,
where these rocks predominate, much of the Lewisian Gneiss, which is the oldest group of
rocks in Britain, dates back to the Archaean, a period in Earth history that ended around
2500 million years ago. The Lewisian Gneiss was formed through several major tectonic
events that repeatedly metamorphosed and deformed what were originally ancient volcanic
and sedimentary rocks. Such was the intensity of metamorphism, that nothing remains of
their original sedimentary and volcanic structure, or the microscopic fossil life present in the
Archaean, geochemistry being the only tool to elucidate the original rock character.
Today the Lewisian Gneiss outcrops within the zone appear as hard quartzo-feldspathic and
hornblende-rich inliers surrounded by the younger Moine rocks. Around 1500 million years
ago, the gneisses formed the bedrock of the southern continental margin of the ancient
Laurentian landmass, which comprised North America, Greenland and Northwest Scotland.
On this continental margin, large quantities of sand and other sediment accumulated,
derived from erosion of the gneisses. These deposits eventually gave rise to the Moine
which underlies much of the zone. Named after the peninsula of a’Mhoine in northern
Sutherland, the Moine Assemblage is composed of three distinct Divisions: the Morar
Division, the Glenfinnan Division and the Loch Eil Division. The precise relationship
between the three divisions is still being debated, but the Morar and Loch Eil Divisions are
regarded as the oldest and the youngest respectively.
The sediment making up the Moine Assemblage is thought to have accumulated over several
hundred million years, between 1500 million and1050 million years ago, to form a pile
several km in thickness upon the ancient Lewisian Gneiss; the Loch Morar Division itself
reaches in excess of 6 km. After the deposition of the sediment pile, the collision of
continental landmasses, through the mechanism of plate tectonics, deformed and
metmorphosed the sediments. The metamorphic and deformational history of the Moine
Assemblage was complex and there were several phases of mountain building, or orogeny,
resulting from continental collision, starting around 1000 million years ago. The various
Page 146
10 January, 2002
sedimentary rocks were metamorphosed to schists and gneisses, with the recrystalisation of
sandstones to quartzites and the more muddier sediments to pelites. The metamorphism
was not entirely uniform, with the result that some portions of the Assemblage were
subjected to high-grade metamorphism, resulting in the formation of gneisses. In contrast,
other areas escaped relatively unscathed, with the preservation of the features characteristic
of the original sedimentary rock, such as layering, dune-bedding, mud-cracks and even ‘fossil’
rain-pits. In places, the rocks were metamorphosed to such a high grade that they were
close to melting point and show evidence of plastic deformation, for example in the central
area of the zone around Lochs Monar and Mullardoch. These high-grade metamorphic rocks
are known as migmatites. Partial melting also took place, resulting in the production of
granite-like masses known as pegmatites, shown to good affect in sites like Carn Gorm,
south-east of Ben Wyvis, and of primary importance in dating tectonic events. Zoisite
mineralisation, formed as a consequence of Moine limestone metamorphism, occurs at the
Gartally Marble Quarries.
The most recent phase of metamorphism and deformation occurred during the Caledonian
Orogeny between 500 million and 400 million years ago. This event folded and
metamorphosed previously deformed metamorphic Moine rock and resulted in the
formation of a major fault line, known as the Sgurr Beag Slide. This slide separates the
Morar and Loch Eil Divisions of the Moine Assemblage along the western margin of this
north Highlands zone.
Another feature of the Caledonian Orogeny in this zone is the Great Glen Fault. This major
fault in Scotland’s crust cuts through the Moine sequence and represents the point where
two blocks of crust, that form Scotland’s foundations, slid past one another. The lateral
displacement of the crust on either side of the fault is major and amounts to many tens of
kilometres, but the fault is no longer interpreted as a terrane boundary like the Iapetus
Suture, that represents the ‘join’ in the crust between Scotland and England, described in
the prospectus for Zone 20. The fault has been reactivated during subsequent periods of
Earth movements and is still active today. South of the Great Glen Fault, components the
Moine Assemblage are thought to represent the base of the Dalradian Supergroup, another
major sequence of sediments deposited on the margin of the Laurentian continent between
700 and 500 million years ago and which underlies much of Zones 9 through to 15.
Large granite intrusions also occur within the zone. South-west of Bonnar Bridge there are
the Carn Chuinneag and Inchbae masses that were intruded into the Moine rocks between
phases in the metamorphism and deformation of the Assemblage. This is evidenced by the
foliated, or banded, nature of the granite rock, which is indicative of deformation and
recrystalisation. The granite in these masses was derived from the actual partial melting of
rocks lower within the crust as the deformation and metamorphism of the Moine
Assemblage took place. The melting resulted in the formation of great masses of silica-rich
melt that moved upward through the crust and which became emplaced within the
deformed and metamorphosed Moine rocks. The Fearn granite (just south of the Kyle of
Sutherland) is known as a Newer Granite, and is one of several plutons, derived through
melting of rocks within the crust, that was emplaced after the metamorphism and
deformation of the surrounding Moine. The Fearn granite intrusion is thought to be just
over 400 million years old.
At the east and south-eastern margin of the zone there occurs the third major rock group
of this zone. These are undeformed and unmetamorphosed sedimentary rocks deposited
Page 147
10 January, 2002
during the Devonian period between 400 and 380 million years ago. At the start of the
Devonian, the Caledonide Orogeny had all but ended and the resulting mountain chain was
being gradually eroded over millions of years, producing sand, silt, mud and other sediment
that accumulated in the basins and hollows within and away from the high ground. Crustal
tensions at this time, rather than pushing the crust together, were instead pulling it apart,
leading to subsidence to the east of the zone in what is now the Moray Firth and the North
Sea. With time, this led to a major sedimentary basin developing in the North Sea area.
NE–SW-trending faults within the zone, such as the southern extension of the Helmsdale
Fault, in places represent the boundary edge of these subsiding sedimentary basins.
The first Devonian (or Old Red Sandstone) deposits were laid down during the lower part
of this period and in the vicinity of Beauly rest with an unconformable contact upon the
Moine metamorphic rocks. Consisting of conglomerates, grits, coarse sands, silts and
mudstones, these deposits would have been deposited by river systems that flowed, in a hot
arid climate, from the high mountainous ground across alluvial fans toward the subsiding
areas in the east. Sediment deposition continued into Middle Devonian times, with sediment
accumulating in the area that is now the Black Isle and along the line of the Great Glen Fault.
In the area that is now the Moray Firth, a vast alluvial plain developed outward from the
Highlands, with the deposition of a range of sediment types from coarse breccias and
conglomerates near the source in the Highlands and at the boundary faults, to fine sands and
silts out on the plain. In the vicinity of Loch Duntelchaig, ancient scree slopes, ‘exhumed’
after millions of years of erosion, rest directly upon the Moine rock, and provide an insight
into the ancient Devonian landscape, in the sediment source area that fed the sedimentary
basin to the north-east. In the basin, a large freshwater lake occupied the area that now
corresponds to Orkney and north-eastern Caithness. Known as the Orcadian Basin Lake,
this body of fresh water fluctuated greatly during the Middle Devonian, depending on
climatic and other environmental conditions. At times of expansion, the lake’s waters lapped
around the eastern edge of the zone, leading to the deposition of finer-grained, lake margin
sediment rather than the normal coarse fluvial deposits. Within these deposits the fossil
remains of a rich and diverse fish fauna are to be found. The fish bed at Black Park,
Edderton, is thought to be the south-eastern extent of the internationally significant
Achanarras Fish Bed, which is thought to extend right through the Orcadian Basin area from
the margins of the Moray Firth across Caithness and into Orkney and Shetland.
3
Palaeontology
The Devonian sedimentary rocks along the coastal fringes of the south-western Moray Firth
represent the marginal deposits of the Orcadian Basin, which extended from this zone
north-eastwards across what is now Caithness and Orkney. Although predominantly fluvial
in character, with numerous alluvial fan deposits, the Devonian sequence contains occasional
deeper-water facies ‘fish beds’ that may be correlated with those further north. These beds
have yielded the remains of a rich and diverse fish fauna that lived and died within the
Devonian lacustrine–fluvial environment. Primitive armoured fish, the lungfish forerunners of
amphibians and reptiles, and the ancestors of today’s bony fish are all represented.
Population studies of the fish beds have suggested that some of the fish species lived entirely
within the ancient basin environment, whereas others migrated from a southern ocean via
an ancient river system. Fish remains found in fluvial portions of the sequences around the
Moray Firth provide evidence of widespread niche utilisation and migratory habits. Deposits
of fossil plant material found in association with the fish faunas provide evidence of the basin
Page 148
10 January, 2002
flora surrounding the lakes and rivers. Perfect three-dimensional preservation of fossil bones
and the prospect of soft tissue preservation at Black Park offers considerable potential for
future research.
4
Geomorphology
The area comprises the high E–W-orientated ridges from Monar to Knoydart. Like Zone 4,
the landscape has been shaped significantly by ice sheets, mountain icefields and corrie
glaciers during the many episodes of cold climate during the Quaternary ice age of the last 2
million years. The pattern of glacial erosion has been strongly dictated by the underlying
controls of structural geology, which both provided lines of weakness that could be easily
exploited by the glaciers and determined the pattern of pre-glacial valleys. Because glacial
erosion has been intense, glens and straths, particularly towards the west, have been
significantly steepened and overdeepened. Pre-existing watersheds, both along the main
divide and between tributary basins, have been lowered by powerful ice streams along the
main lines of ice discharge. There is thus a highly interconnected pattern of valleys, which
serves to isolate the main mountain massifs and ridges. This is most evident in the
mountains of Wester Ross where the Torridonian sandstone mountains rise abruptly above
ice-scoured plateau surfaces. Elsewhere there is a strong W–E or SW–NE trend to the
valleys and ridges. In the east of the area, plateau surfaces are more extensively developed
and are ice scoured, as north of Loch Ness.
Many of the higher mountain summits and higher slopes were free of ice when icefields and
glaciers filled the valleys below. These areas were exposed to intense frost activity and
generally have a cover of frost-weathered blocks and detritus, in some areas sorted into
patterned ground. On most slopes this debris has been redistributed by mass movement
processes to form solifluction lobes and terraces. These are spectacularly developed in the
Fannich Mountains (e.g. Sgurr Mor) and on Ben Wyvis. During and following deglaciation,
corrie headwalls and other cliffed slopes below the summits continued to disintegrate
through rockfalls and rockslides, producing scree slopes below.
There is a variable cover of drift on the lower slopes of the mountains and in the glens. This
may appear as a rather featureless spread of till (boulder clay), but in many areas there are
clear constructional features in the form of a variety of moraine ridges and mounds
associated with the Loch Lomond Readvance, as in Glen Carron, Glen Doe (associated with
ice-dammed lakes), Glen Moriston and in the Fannichs (at Loch Glascarnoch and upper
Gleann na Sguaib). Sand and gravel deposits are rare, notably associated with the formation
of large deltas in an ice-dammed lake at Achnasheen. The zone is remarkable for the
occurrence of several large ice-dammed lakes and their associated landform assemblages.
These include Achnasheen (delta terraces), Glen Doe (cross-valley moraines and washed
bedrock) and, most spectacularly of all, Glen Roy. Although not including Glen Roy itself,
the zone includes part of the wider landform assemblage associated with the formation and
drainage of the ice-dammed lakes that formed in Glen Roy, Glen Gloy and Glean Spean
during the Loch Lomond Stadial. These features include end moraines, lake shorelines,
deltas, fans, cross-valley moraines and drainage channels. Where not covered by drift, the
lower slopes of the mountains and the floors of the glens frequently show evidence of glacial
scouring in the form of roches moutonnées, rock steps and ice-moulded bedrock. In the
eastern part of the zone, a good example of last ice-sheet meltwater channels occurs at
Struie.
Page 149
10 January, 2002
Some of the periglacial features on the higher slopes and summits continue to be active
today under a combination of wind and frost-assisted processes. Many steeper slopes are
prone to debris flow activity (as in Glen Docherty). The schist mountains are also prone to
landslipping, and many examples of full or partial rock slope failures occur across the area
(e.g. on Ben Attow and the Glen Affric hills).
The Northern Highlands zone contains rivers draining both west and east of the central
watershed, but the easterly flowing rivers dominate the zone, and they, in turn, are heavily
dominated by the presence of E–W-orientated lochs within the upper and middle reaches of
the rivers (e.g. Loch Garry, Loch Cluanie, Loch Loyne, Loch Meiklour, Loch Affric and Loch
Arkaig). Some lochs have been dammed for hydro-electric power generation or water
supply. This can affect the base level of the system and the increased channel division
(through sediment deposition) around Dundreggan Reservoir (River Moriston) may be
related to such a change. Inter-catchment water transfer can also alter the rates of channel
change in both the source and receiving catchments. Water levels in Loch Ness were raised
when the Caledonian Canal was completed. This had a profound effect on the confluence of
the River Coiltie, which has actively aggraded since then, producing a highly dynamic
environment. The River Enrick, the neighbouring catchment, was not affected to the same
extent by the change in base level. The explanation for this can be found upstream, with the
Coiltie being incised into bedrock and constrained for much of its length while the Enrick
has a wider floodplain and was able to adjust to the change in base level through meandering
upstream. The mouths of the River Garry, River Moriston and River Enrick have all
prograded into Loch Ness as a result of their sediment load and the change in base level.
The middle and lower reaches of the main stem rivers are, in the main, meandering,
although the lower reaches of the River Loy are unusually straight for a river in this zone.
Some rivers display an element of channel division and braiding within the middle reaches
and many have braided upstream reaches. The meanders on the River Glass are unusual for
their size, degree of irregularity, length of meandering reach and because of the persistence
of palaeomeanders and meander cut-offs on the floodplain. The Beauly, the Carron and the
lower River Conon also meander but to a lesser extent than the Glass, with the Conon
being susceptible to flooding of its locally wide floodplain. The Black Water and the Bran
have extremely irregular, tortuous meanders in their upper reaches. The Abhainn an t’Srath
Cuilleannaich (a tributary of the Carron) provides an excellent example of an actively
meandering upland stream within an alluvial basin. In general, tributaries in this zone take
two forms: short mountain torrents which drain directly into the lochs, forming alluvial fans
at their base; and dendritic meandering and braided networks, often with small lochans and
areas of bog within them, which drain lower-lying or more gentle gradient hillslopes.
5
Soils
The upland soils in this zone are mainly formed upon acid drift materials, resulting in a large
range of podzolic soils. The high peaks are devoid of soil-forming materials and there are
substantial areas without soil surfaces. Approximately a quarter of all soils in this zone are
classified as montane, including alpine podzols. In lower-lying regions and/or those with
impeded drainage at depth, surface-water gleys predominate. The soils of this zone have an
inherently low fertility in terms of agricultural productivity but support unique montane
vegetation and associated habitats. Iron podzols associated with old Caledonian pine forests
are of national significance, as are the periglacial features associated with montane soils of
Page 150
10 January, 2002
the Fannich mountains. Soil loss from peat erosion is an ongoing natural process that is
aggravated by changes in land use on steep slopes.
6
Summary of key Earth science features in the Northern
Highlands
The principal Earth heritage interests in the Northern Highlands are summarised in Table
7.1. The Northern Highlands includes a total of 22 GCR sites.
Table 7.1
GCR sites in the Northern Highlands
GCR block
No. of sites
Principal interests
Moine
7
Non-marine Devonian
1
Vertebrate Palaeontology
1
Mineralogy
2
Quaternary of Scotland
7
Mass Movement
Fluvial Geomorphology
1
2
Representative sections of the Moine
Assemblage
Representative sites for Devonian
palaeoenvironment and palaeoecological
studies
Fossil fish remains of international
significance
The occurrence of zoisite and other rare
and unusual minerals
Glacial and glaciolacustrine landforms
associated with Loch Lomond ice-dammed
lakes; periglacial landforms; meltwater
channels; Loch Lomond Readvance
moraines
Large-scale rock slope failure features
River meander landforms and processes
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the Northern Highlands are summarised in Table 7.2. However, there is no
systematic information on current impacts or trends.
Page 151
10 January, 2002
Table 7.2
Potential pressures and vulnerability of Earth heritage interests in the Northern
Highlands
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction, infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; river management
Generally robust
Vulnerable to ad hoc river engineering and management;
river engineering and management; afforestation gravel
extraction;land management changes
Vulnerable to land management changes
Vulnerable to enhanced erosion through overgrazing and
increased recreational pressures
Palaeontological interests
Quaternary depositional landforms
and exposures
Landscapes of glacial erosion
Fluvial geomorphology
Soils
Periglacial geomorphology
8
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Fossils are collected from the fossiliferous exposures. The Black Park fossil fish site has
been targeted by irresponsible collectors resulting in damage to the resource.
Bibliography
Ballantyne, C.K., Sutherland, D.G. and Reed, W.J. (1987) Wester Ross Field Guide. Quaternary Research
Association, Cambridge.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. GCR Series No. 16. Joint Nature
Conservation Committee, Peterborough.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Gregory, K.J. (1997) Fluvial Geomorphology of Great Britain. Geological Conservation Review Series No.
13. Chapman and Hall, London.
Johnstone, G.S. and Mykura, W. (1989) British Regional Geology: The Northern Highlands of Scotland (4th
edition). British Geological Survey. HMSO, London.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
10
Maps
British Geological Survey Maps: 1:50,000 sheets: 62, 63, 72, 73, 82, 83, 92, 93, 102.
Page 152
10 January, 2002
Soil Survey of Scotland Maps: 1:250,000 sheets 3 and 4 encompass Zone 7 and uncoloured 1:50,000
sheets 20,25 and 26 cover most of the Northern Highlands. MLURI, Aberdeen.
Page 153
10 January, 2002
ZONE 8
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
WESTERN HIGHLANDS
Highlights
Torridonian Sandstone exposures on Skye.
South-western exposures of the Moine Assemblage.
Location of the Strontian lead vein and the first recorded occurrence of Strontianite.
The occurrence of the minerals brewsterite and harmotome.
The most extensive mainland occurrence of Cretaceous rocks in Scotland.
Possible location of the K–T boundary.
Remnants of the Tertiary basalt lava plateau in Morvern.
Classic landscape of glacial erosion (ice-scoured dissected mountains).
Representative examples of Loch Lomond Readvance landforms, including outwash
surfaces and moraines, and links to sea levels.
Representative records of Late-glacial and Holocene palaeoenvironmental change,
including forest history and human impacts on the landscape.
Detailed records of Late-glacial and Holocene sea level changes preserved in isolation
basins.
Classic fjordic coastline.
Exemplary development of loch head saltmarsh.
Representative examples of raised shore platforms and beaches.
Lochs within the lower reaches of major river systems.
Geology
Zone 8 is dominated by rocks belonging to the Moine Assemblage. The Moine is a series of
three groups, disposed with a roughly NE–SW trend. From west to east, they are termed
the Morar, Glenfinnan and Loch Eil Groups. The Moine was deposited on a shallow, gently
subsiding continental shelf, in two marine basins. Deposition is thought to have started
around 1000 million years ago. The Morar and Loch Eil Groups now predominantly
comprise metamorphosed sandstone, whereas the Glenfinnan Group contains much more
metamorphosed mixed units – originally muds and muddy sands.
The Moine was deposited on a bedrock of Lewisian Gneiss. Remnants of the gneiss occur in
the west of the zone, the largest fragment occurs at Glenelg, and is known as the Glenelg
inlier. It comprises a mixed assemblage of acid gneisses, with marbles, calc-silicates and
pelites. Importantly, it also contains eclogite, a rock type characteristic of high-pressure
metamorphism, often associated with the subduction process. Much of this assemblage is
exposed along the Dornie–Inverinate road section at Totaig and at Allt Cracaig, although
the latter is almost impossible to study because of afforestation.
The Moine has been deformed several times, resulting in areas of highly complex folding.
The latest deformation episode occurred during the Caledonian Orogeny, when ‘Scotland’
collided with ‘England’. Folding of the Moine in this area follows a characteristic pattern. East
of a line taking in Loch Quoich, the folds are relatively flat-lying; west of this line, the folds
are steep and upright. This line is known as the Loch Quoich line, and the area west of it,
the Highland Steep Belt. A full traverse through the various Moine Groups and the steep
belt, with its upright folds, is provided by the Fassfern–Lochailort road section.
Page 154
10 January, 2002
During deformation, slides (low-angle thrust faults) formed. These are high-strain zones
above which rock masses moved. Rocks within these zones are characteristically laminated,
or platy. One of the most important tectonic breaks in Zone 8 is the Sgurr Beag Slide. It
separates the Morar Group from the Glenfinnan Group. It has been folded, and
consequently has a complex outcrop pattern. Excellent exposures occur at Kinlochourn,
Lochailort and Glen Shiel.
Another major break, the Moine Thrust, occurs in the north. It forms part of a zone of
thrusts – the Moine, Balmacara and Kishorn thrusts. The thrusts separate the geology into a
series of packages or nappes. The nappes contains a variety of rock types: Moine, Lewisian,
Torridonian and Cambrian.
Several intrusions occur in the zone. The oldest, the Ardgour granitic gneiss, is thought to
be around 1000 million years old. Several younger intrusions are associated with the
Caledonian Orogeny. The Glen Dessary syenite, dated at around 456 million years, is
important for providing a maximum for the steep belt deformation in this area, given that
the body was intruded prior to the last phase of deformation. The Strontian granite, the
largest new granite in the Northern Highlands, occurs in the south, where its SE portion is
truncated by the Great Glen Fault. The granite is associated with barium, lead and zinc
mineralisation and is the location where strontianite was first recorded, from which the
element strontium was first isolated in 1791. Brewsterite and harmotome are other rare
minerals found at Strontian, this being the type locality for the former.
The zone also contains a large outcrop area of Torridonian Sandstone on the eastern tip of
Skye and on the adjacent mainland east of Kyle of Lochalsh. The Torridonian within Zone 8
is subdivided into two distinct groups, the older Sleat Group (named after the Sleat
peninsula) and the younger Torridon Group. Deposited around 800 to 700 million years
ago, the Sleat and Torridon Groups represent sediment deposited in rift valleys that
developed on the Laurentian continental margin. The lowermost Torridonian sediments rest
upon and infill an ancient landscape that had been eroded into the old Lewisian Gneisses.
The lack of subsequent metamorphism of the sediments has meant that all of the original
features of the sediments, including layering, dune-bedding, mudcracks, rain prints and some
microscopic fossils (found in other zones on the mainland) are often perfectly preserved,
revealing a lot of information concerning the precise environmental conditions in which the
sediment was laid down.
Although originating as loose sediment on the south-eastern margin of the Laurentian
continent, the Torridonian is younger than the Moine, and in contrast to the Moine rocks, is
relatively undeformed, having not been subjected to successive metamorphic events.
Formerly thought to have formed contemporaneously with the Moine, the precise
relationship between the Moine and the Torridonian is still poorly understood.
By late Cretaceous times, around 95 million years ago, portions of Zone 8, along with much
of the west coast, was submerged beneath a shallow tropical sea and there was widespread
sediment deposition across what is now Britain. Only a few of the highest areas were left
above sea level. In the Hebrides area, calcareous sandstones were deposited followed by a
thin layer of chalk. Although nowhere thicker than 4 m, the chalk is directly analogous to
the huge thicknesses outcropping on the Antrim Coast and the south coast of England. The
zone encompasses the largest area remaining of this once extensive cover of Cretaceous
sediment within Scotland, this is well preserved At Beinn Iadain, north of Loch Aline.
Page 155
10 January, 2002
At the end of the Cretaceous Period, the area was lifted above sea level and subjected to
erosion. Above the Cretaceous sequences on Morvern and in Mull a thin, brown layer of
clay, from the early Tertiary Period, represents altered volcanic ash, which marks the onset
of the last phase of volcanic activity in Britain. This activity, which lasted for around 12
million years, was associated with the split of northern Europe from Greenland and North
America, with the formation of the northern North Atlantic. This volcanic activity within the
zone therefore represents part of a much larger area of activity that extends along the
eastern seaboard of Greenland, the western margin of the Rockall Plateau, through the
Faeroes and Iceland. Volcanic ash was the first surface product of the activity ahead of huge
outpourings of lava that piled up to a maximum thickness of 3000 m. The lavas were
principally fed from fissures similar to those in present-day Iceland. The lavas, which were of
basaltic composition, covered the eroded land surface of Zone 8 comprising the
Precambrian to Cretaceous age rocks. An eroded fragment of the once extensive lava pile
occurs on Morvern at Beinn Iadain, and imparts upon the mountain a characteristic stepped
topography.
Recent studies have indicated that the sedimentary sequence preserved under the Tertiary
lavas on Beinn Iadain, may span the Cretaceous–Tertiary (or K–T) boundary, the period in
history when the dinosaurs died out, and this would be the only such site in the UK.
3
Palaeontology
Within the Mesozoic sequence at Beinn Iadain and Beinn na h’Uamha on Morvern, rare
marine fossils have been found. In the same area, fossil plant remains are to be found in a
thin layer of Tertiary age sediments.
4
Geomorphology
This area principally comprises the mountains from south of Applecross through Knoydart
to Morvern. The mountains are heavily dissected with corries and extensive ice-scoured
slopes. The intervening troughs and rock basins have been overdeepened by glacial erosion,
although their locations and forms are largely controlled by the underlying geological
structure. Spectacular fjords occur where the sea has flooded the lower reaches of the
glacial troughs. Much of the area is rocky, and drift deposits are confined to a few glens
associated with the Loch Lomond Readvance, notably Glen Tarbert. Loch Lomond
Readvance outwash deposits are well developed at Arisaig and near Acharacle, where they
grade into raised beach deposits. The area is important for studies of sea level change,
particularly for the records preserved in isolation basins, as at Kentra, Rumach and Loch nan
Eala
There are few detailed pollen records of vegetation history from this zone (e.g. Claish
Moss). The middle Holocene woodland was dominated by birch, with oak and elm in
favourable locations in the south.
The coastline of this zone reflects essentially the profound effects of successive glaciations.
Although isostatic uplift is now causing a relative fall in sea level across the zone, most of
the sea lochs and sounds represent drowned glacial valleys originally formed during periods
when the sea level was much lower than it is today. The deeply indented character of the
coastline and the protection from extreme wave energy afforded by the Inner Hebrides
Page 156
10 January, 2002
result in sheltered conditions along most coastlines. This shelter is reflected by the
existence, at the head of many sea lochs, of expanses of mud or sandflats and saltmarsh,
particularly extensive marshes occurring in Loch Carron. The existence of enhanced rates
of deposition and erosion on these coasts in former times is reflected in the presence,
intermittently around the loch shores, of fragments of raised shore platforms and beaches
as, for instance, around Lochalsh and at Strome Ferry.
On outer, west and south-west facing shores, wave conditions are more vigorous, and
consequently dynamic sandy beaches are more common. Nowhere is this more evident
than along the coastline of Morar, south of Mallaig, where numerous clean sandy beaches
have collected between successive rocky headlands. With the mountains of Rum providing a
spectacular backdrop, these features combine to create a coastline of stunning beauty, as
seen in the film Local Hero.
Some of the major rivers in the Morvern peninsula (e.g. River Rannoch, Black Water and
Glengalmadale River) display evidence of irregular meanders and channel division in the
middle and lower reaches. The existence of lochs in their middle reaches might have served
to rejuvenate the downstream reaches, giving them characteristics of braided meanders,
which are more commonly found upstream. The River Aline has an unusually straight course
in the reach downstream of Loch Arienas, which may be geologically controlled. The
Abhainn a’Ghlinne Ghil has an extensive upland tributary network but the meander train
and floodplain width is more restricted than that of the Black Water, where the wide, flat
floodplain gives rise to irregular meanders in what appears to be an upland basin. The
Glengalmadale River also has an extensive upland tributary system but here the tributaries
are very straight and steep, causing fast run-off and ensuring that the river bed comprises
coarse material.
The major river system of Moidart is the Shiel, with Loch Sheil dominating the area. A
number of short, steep upland tributaries feed into the loch, with the confluence of the
Glenaladale River being a fan which is unusual in this zone. There is only a short reach of
river meandering within a wide floodplain downstream of the loch outflow. Lochs are a
persistent feature of the rivers in Moidart, with some of the other major rivers (Moidart,
Polloch, Ailort, Gour) draining through lochs in their middle and lower reaches. There is an
extensive network of upland tributaries within Moidart, most of which are steep and
straight. The sinuous planforms with limited division in the upper and middle reaches of the
rivers Gour, Strontian, Scalladale and Cona suggest that they are all wandering gravel bed
rivers. The rivers Dessary and Pean flow east out of the zone into Loch Arkaig and have
well-developed meanders. The floodplain of the River Dessary, in particular, is extremely
wide in its middle reaches and is akin to an alluvial basin. The Morar peninsula is also
dominated by a loch, Loch Morar, with the rectangular meanders of the River Meoble, its
main tributary, being unusual in this zone. In contrast, the lower reaches of the Carnach and
Inverie Rivers, in Knoydart, and the lower reaches of the River Shiel, the Glenmore and
Gleann Beag, in Kintail, meander through wide, well-developed floodplains. Upstream the
rivers and their tributaries are more constrained, with short, steep boulder bed tributaries.
These rivers do not have significant lochs within their lower reaches.
Page 157
10 January, 2002
5
Soils
This is one of the classic areas in which geology plays an important, if indirect, role in
controlling the development of soils; altitude and slope aspect are the overriding controls
on soil development, but these are a function of the underlying solid geology. In the E–W
(or NE–SW) valleys, the soils on the north-facing slopes are markedly different from those
on the south-facing slopes. Brown earth soils make up 6% of the soils and are found on the
lower sheltered slopes; and surface-water gleys (51%) on gentler slopes. Typically nutrientpoor, acid podzols derived from quartz-rich rocks make up 19% of the soils. The remainder
comprise montane soils (19%), with very little peat (1%), confined to distinct basins. There is
a strong climatic effect on the development of soils because of the proximity to the west
coast, and a strong altitude effect. Thus, there is a complex distribution of soil associations,
characterised by short-range variability controlled by landforms, especially slopes. Soils of
national significance include rendzinas in the river Kishorn area and montane soils on Ben
Attour.
6
Summary of key Earth science features in the Western
Highlands
The principal Earth heritage interests in the Western Highlands are summarised in Table
8.1. The Western Highlands includes a total of 28 GCR sites.
Table 8.1
GCR sites in the Western Highlands
GCR block
No. of sites Principal interests
Torridonian
Moine
Caledonian Igneous
1
21
3
Mineralogy
Cenomanian–Maastrichtian
Mass Movement
2
1
1
7
A representative section of the Torridonian Sandstone
Representative sections of the Moine Assemblage
Igneous rocks formed as a result of the Caledonian
Orogeny
The occurrence of rare and unusual minerals
Representative sections of late Cretaceous sequences
Rock slope failure features
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the Western Highlands are summarised in Table 8.2. However, there is no
systematic information on current impacts or trends.
Page 158
10 January, 2002
Table 8.2
Potential pressures and vulnerability of Earth heritage interests in the Western
Highlands
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction, infilling of quarries and mines;
vulnerable to irresponsible collecting
Generally robust
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments; land
management changes; construction of tracks; afforestation;
river management
Vulnerable to enhanced erosion through overgrazing and
increased recreational pressures
Vulnerable to drainage of bogs and peat extraction
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Generally robust to all but large scale developments such as
superquarries
Vulnerable to sea level rise where constrained by development
on landward side
Vulnerable to river engineering and management;
afforestation; gravel extraction; land management changes
Vulnerable to land management changes, pollution
Palaeontological interests
Mineralogical interests
Landscapes of glacial erosion
Quaternary depositional landforms
and exposures
Periglacial geomorphology
Palaeoenvironmental records
Records of sea level change
Rock coast features (Fjordic
landforms)
Loch head saltmarshes
Fluvial geomorphology
Soils
8
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Regions 15 and 16. North-west Scotland: The Western Isles and West
Highland. Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
HR Wallingford (2000) Coastal Cells in Scotland. Cell 5 – Cape Wrath to the Mull of Kintyre. Report to
Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and
Historic Scotland. SNH RSM Report No. 147. Battleby.
Johnstone, G.S. and Mykura, W. (1989) British Regional Geology: The Northern Highlands of Scotland (4th
edition). British Geological Survey. HMSO, London.
Mather, A.S. and Crofts, R. (1971) The Beaches of West Inverness-shire and North Argyll. Dept. of
Geography, University of Aberdeen. Countryside Commission for Scotland, Perth.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Dept. of
Geography, University of Aberdeen. Countryside Commission for Scotland, Battleby, Perth.
Page 159
10 January, 2002
May, V. and Hansom, J.D. (in press) Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Shennan, I. (1994) Late Quaternary Coastal Records of Rapid Change. Field Guide for the First International
Meeting Symposium and Field Excursion, Dunblane and Fort William, September 1994. Department
of Geography, University of Durham.
Shennan, I., Green, F.M.L., Innes, J.B., Lloyd, J.M., Rutherford, M.M. and Walker, K. (1996) Evaluation of
rapid relative sea-level changes in north-west Scotland during the last Glacial-Interglacial transition:
evidence from Ardtoe and other isolation basins. Journal of Coastal Research, 12, 862–874.
Shennan, I., Tooley, M.J., Green, F.M.L., Innes, J.B., Kennington, K., Lloyd, J.M. and Rutherford, M.M.
(1999) Sea level, climate change and coastal evolution in Morar, northwest Scotland. Geologie en
Mijnbouw, 77, 247–262.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland, Methuen, London.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 44, 52, 53, 61, 62, 71, 72.
Soil Survey of Scotland Maps: 1:250,000 sheet 4 encompasses Zone 8 and uncoloured 1:50,000 sheets
33, 40 and 49 cover the Western Highlands. MLURI, Aberdeen.
Page 160
10 January, 2002
ZONE 9
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
NORTH-EAST COASTAL PLAIN
Highlights
The easternmost extension of the Dalradian Supergroup.
Peterhead and Aberdeen granites.
Ultrabasic intrusions which help elucidate magmatic processes.
Devonian sedimentary sequences.
Southern margin of the Orcadian Basin with fossil fauna.
The fossil remains of the world’s oldest known complete terrestrial wetland ecosystem,
perfectly preserved in the Rhynie Chert.
The most extensive and best preserved ‘pre-glacial’ landsurfaces in Scotland, with
associated inselbergs, deep weathering and cover deposits.
Classic landscape of limited glacial erosion.
Preservation of long sequences of Quaternary deposits, including glacial, interglacial and
interstadial deposits that provide some of the longest records in Scotland.
Glacial and glaciofluvial landforms including ice-sheet moraines, eskers and meltwater
channels.
Classic area for lowland periglacial features.
Representative records of Late-glacial and Holocene palaeoenvironmental change,
including forest history and human impacts on the landscape.
Stratigraphic records of Late-glacial and Holocene sea level change.
Exemplary suite of granite cliff landforms.
Exceptional size, diversity and continuity of beach/dune landforms.
Longest continuous stretch of sand dunes in Scotland.
Most extensive area of bare sand in Scotland.
Highest individual sand dunes and highest average dune height (of any NHZ) in Scotland.
Exemplary parabolic dunes.
Geology
The North East Coastal Plain is dominated by rocks of the Dalradian Supergroup, which
extend into neighbouring Zones 12 and 21 and further afield into Zones 6, 10, 11, 13, 14
and 15. Predominantly quartz-, feldspar- and mica-rich, the rocks of Zone 9 represent a
metamorphosed and structurally deformed pile of marine sediments and volcanic rocks,
with a total thickness of approximately 25 km. Underlying more of the Scottish landscape
than any other group of rocks, the Dalradian is long established as a classic focus for the
study of rock metamorphism (alteration by intense heat and pressure) and deformation
arising from continental collision.
Confined to the area defined by the Great Glen Fault to the NW and by the Highland
Boundary Fault to the SE, the Dalradian sediments and volcanics were originally laid down,
or in the case of the volcanics erupted onto, the southern margin of a continent referred to
by geologists as Laurasia, during the Precambrian and Cambrian periods between 700 and
600 million (and very possibly as recent as 500 million) years ago. The Laurasian continent
comprised North America, Greenland and the north-westernmost part of present-day
Scotland and was separated from what is now England and northern Europe by the Iapetus
Ocean.
Page 161
10 January, 2002
As the sediments accumulated at the continental margin of Laurasia, the area subsided,
forming a basin into which the vast thickness of the Dalradian sedimentary and volcanic pile
accumulated; ongoing crustal instability as the basin formed gave rise to the volcanic activity.
As the basin developed and filled, over many millions of years, a variety of sediments,
including gritstones, sandstones, siltstones, mudstones, shales and limestones, were laid
down, reflecting variation, spatially and temporally, in the depositional environment. Much of
this reconstruction has been pieced together over many years of study since the late
nineteenth century, involving detailed mapping of the area. This work has also led to the
division of the Dalradian into four parts: the Grampian, Appin, Argyll and Southern Highland
Groups. The Argyll and Southern Highland Groups, the two uppermost groups, underlie
most of Zone 9, with a small portion of the Grampian Group; there is apparently no Appin
Group within the zone.
In late Cambrian and through Ordovician times, the Dalradian Supergroup underwent
deformation and metamorphism as the Iapetus Ocean closed, with the continental collision
between Laurasia and a northern European continental landmass. This gave rise to the
eventual coming together of the crustal foundations that constitute Britain. On a large scale,
the collision gave rise to an alpine-scale mountain belt, termed the Caledonides, which
structurally is represented by large-scale folding within the rock layer sequences and a
strong NE–SW grain across the zone. The overall structure of the area is one of large openstyle folds, refolding tighter folds. Excellent exposures occur along the coastal strip.
Concurrently with the deformation, the various sedimentary rocks were metamorphosed,
with the recrystalisation of sandstones to quartzites, muddy sands to pelites and mudstones
to phyllites and slates. The area between Portsoy and Portknockie encompasses a large
variety of rock types, including mica-schist and limestone. East of Portsoy, the
metamorphism in this zone is characteristic and is referred to as Buchan style metamorphism.
Intense metamorphism lower in the crust resulted in the actual partial melting of rocks,
producing great masses of silica-rich melt that moved upward through the crust and became
emplaced within the deformed and metamorphosed Dalradian. The granites of Peterhead,
Aberdeen, Bennachie and Crathes are examples of these plutons. In contrast to the granites,
the zone encompasses other major intrusions of ultramafic character, the largest being the
Insch intrusion. These are silica-poor, base-rich bodies of largely gabbroic rock, some of
which are mineralogically layered. The largest is the Insch intrusion; Belhelvie, Maud and
Arnage are other examples. Formed from basic magma, locations such as the Hill of Barra
within the Insch intrusion are valuable in understanding magmatic processes.
As the Caledonian Mountains were uplifted and eroded, sediment derived from them
accumulated in mountain hollows and in the low adjacent areas. During Devonian times,
sediments (mainly conglomerates and sandstones) had accumulated over a large area of the
zone. Subsequent erosion has largely removed this sediment cover and today a broad
swathe of Devonian sediment SSW of Pennan and small ‘outliers’ north of Aberdeen,
around Lumsden and south of Cullen, represent remnants of the once more extensive
outcrop.
3
Palaeontology
The southern and south-eastern margins of the Moray Firth represent the southern limits of
the Orcadian Basin. Although dominated by fluvial deposits, the Middle Devonian sequences
Page 162
10 January, 2002
contain ‘fish beds’ that represent the greatest extent of the Orcadian Basin Lake. The fish
faunas present within these deposits are typical of a lake margin setting and include bottomdwelling armoured types, the lungfish forerunners of amphibians and reptiles, and the
ancestors of today’s bony fish. Middle Devonian fluvial sediments at the Den of Findon have
to date yielded a fossil fish fauna, found largely within nodule beds, typical of a marginal
setting within the Orcadian Basin.
In the vicinity of Rhynie, Aberdeenshire, a basin of Devonian-age sediments lies within
Dalradian metamorphic rock. The Devonian sedimentary sequence has provided the fossil
remains of the world’s oldest known terrestrial wetland ecosystem in the form of the
Rhynie Chert. Within the hot-spring-derived chert, perfectly preserved three-dimensional
plant and arthropod fossils occur in intimate association with a diverse plant flora, elements
of which are in growth position. This chert deposit also yields the fossil remains of the
world’s oldest known insect, fossil bacteria, algae, fungi and representative growth stages of
various plants. Rhynie is truly a site of major international importance.
4
Geomorphology
This zone includes the coastal lowlands of the Moray Firth, and to the south the area of
Buchan and the coastal lowlands of Aberdeenshire. The inland area of Buchan comprises a
series of old erosion surfaces that pre-date the ice age. Buchan is the best-preserved preglacial landsurface in Scotland, reflecting its tectonic stability and low intensity of glacial
erosion – it has the deepest and most intensely weathered rocks (e.g. Pittodrie and Hill of
Longhaven), topographic basins, tors (Bennachie), inselbergs (Mormond Hill, Binn of Cullen)
and pre-glacial gravels (Buchan Ridge gravels at Windy Hills and Moss of Cruden). It
provides the clearest expression of a pre-glacial landscape in Scotland. The total assemblage
of pre-glacial features occurring within a glaciated area is unique in Britain and of
international importance. The nearest analogues are in Devon and Cornwall (unglaciated)
and parts of Pembrokeshire. Internationally, Buchan compares with northern Sweden and
Finland, where pre-glacial landform elements have also survived glaciation. Although Buchan
has largely escaped significant glacial erosion, glacial deposits and meltwater channels are
widespread. Till sheets occur extensively in the coastal plain between Elgin and Aberdeen.
Because the movement of the ice was onshore, both from the Moray Firth and the North
Sea, erratics include materials derived from the seafloor (e.g. at Boyne Quarry and
Gardenstown). Because the intensity of glacial erosion has been low, crucial deposits predating the last ice sheet are preserved at a number of localities. These include interstadial
and interglacial deposits of considerable significance for the records of landscape evolution
and palaeoenvironmental conditions that they contain. Among the key sites are Kirkhill,
Teindland, Crossbrae, Bellscamphie, Camp Fauld and Howe of Bythe. Glaciofluvial deposits
associated with the melting of the last ice sheet are particularly well developed north of
Aberdeen (Kippet Hills), and a section at the Bay of Nigg records the interaction of inland
ice and ice moving north-eastwards from Strathmore. Possible stillstands or readvances of
the ice have been recognised at Elgin (Elgin Oscillation) and west of Fraserburgh. Shells from
the local equivalent of the Errol Beds at St Fergus have provided a key radiocarbon date (c.
15 ka BP) for the deglaciation of the coastal area. Buchan is also noted for its assemblages of
lowland periglacial features, including ice-wedge casts and polygons, cryoturbated soils and
extensive solifluction deposits. The coastal area also provides important detailed records of
Holocene relative sea level changes in an area peripheral to the main centre of isostatic
uplift in Scotland (Philorth Valley, lower Ythan Valley).
Page 163
10 January, 2002
There have been relatively few studies of the vegetation history of the zone. During the
middle Holocene, birch–hazel–oak woodland was predominant in the coastal lowlands, with
pine–birch towards the western margins of the zone.
The coastal zone was largely dominated by glacial deposition, which has provided an ample
sediment supply for the development of extensive areas of raised beach sand dune and
shingle beach development, as at Culbin, Spey Bay, Rattray and Sands of Forvie, for example.
Intervening areas of coastline show well-developed cliffs and shore platforms developed in a
variety of rock types. Inland from the coast, glaciofluvial sands and gravels occur extensively
to the west of the Spey; to the east and south till sheets predominate. The major valleys
such as the Spey, Ythan, Don and Dee also acted as sediment sources to the coast during
and following deglaciation.
The North East Coastal Plain is characterised by two distinctive, yet strikingly different,
coastal morphologies. Along the east-facing coast, south of Fraserburgh, dune systems
dominate, and between Aberdeen and Collieston they form the longest continuous stretch
of these landforms in the country. Along with those further north, these dunes also attain
the highest mean elevation – approximately 11 m, twice the national average – of any NHZ.
A broad range of beach- and dune-related features is preserved, including dune ridges,
parabolas, blowouts, deflation plains and, at Forvie, extraordinary expanses of drifting bare
sand. These dunes are broken only by occasional lengths of rocky, cliffed coastline, although
the landforms preserved may nonetheless be exceptional as, for instance, at the imposing
granite cliffs of the Bullars of Buchan.
The north-facing coastline of the zone contrasts markedly to that further south, being
dominated instead by rugged, cliffed coasts interspersed with only occasional sandy or stony
beaches. Although striking from a landscape perspective, few of these landforms are
exceptional from a geomorphological viewpoint.
The North East Coastal Plain contains the lower reaches and river mouths of a number of
major rivers. The low gradient means that the rivers are, in the main, meandering or
sinuous in this zone; for example, the lower reaches of the Don have a number of tortuous
meanders, whereas the Dee is more sinuous, although the bed material in both these major
rivers remains gravel- or cobble-sized all the way to the sea. The entire Ythan catchment
falls within this zone and, as it has no true ‘upland’ reach, the whole catchment is low energy
and either sinuous or meandering. There are small headward-migrating waterfalls in the
Ythan catchment that reflect the long-term catchment response to the last glaciation. The
North and South Ugie meander tortuously within a nitrate-sensitive catchment, moving
position mainly by cutting back the banks. The Dee, the Don, the Ythan and the Ugie Water
all drain east, whereas the Deveron changes direction around Turrif, having been northeasterly then suddenly becoming north flowing. This may be due to headwater capture or to
geological influence. Much of the Deveron lies within Zone 9 but its headwaters and the
headwaters of tributaries lie in Zones 11 and 12.
5
Soils
The majority of the soils in this zone (56%) are podzols, which are heavily leached soils.
Specific soil associations depend on the drift cover (thickest in valleys and depressions), but
tend to be podzolic and acid because of the climate and the coarse parent materials on
Page 164
10 January, 2002
which the soils have formed. Brown forest soils are also significant and are developed on
base-rich parent materials (gabbro intrusions) above 300 m, but these are relatively rare
compared with podzols and gleys. The soils in this zone are agriculturally productive, despite
low pH and nutrient status, by virtue of soil texture, topography and climate, which enable
intensive arable cultivation. The distinction between podzols and brown earths that have
been cultivated becomes difficult as both have been extensively modified and they have lost
the detail of their surface horizons. Basin peat deposits are found as remnants of much
larger peatlands within the zone, some of which are of national significance. Brown
magnesian soils of the Leslie association formed on isolated ultrabasic rocks/drift are also
considered nationally important.
6
Summary of key Earth science features in the North East
Coastal Plain
The principal Earth heritage interests in the North East Coastal Plain are summarised in
Table 9.1. The North East Coastal Plain includes a total of 28 GCR sites.
Table 9.1
GCR sites in the North East Coastal Plain
GCR block
No. of sites Principal interests
Dalradian
Caledonian Igneous
5
5
Palaeobotany
Palaeoentomology
Arthropods
1
1
1
Vertebrate Palaeontology
Quaternary of Scotland
1
11
Coastal Geomorphology
3
7
Representative sections of the Dalradian Supergroup
Igneous rocks formed as a result of the Caledonian
Orogeny, important in understanding magmatic processes
A diverse Devonian plant fossil flora
Fossil remains of the earliest fossil insects
Fossil remains of some of the earliest terrestrial
arthropods
Devonian fossil fish remains
Weathered bedrock and cover deposits associated with
pre-glacial land surfaces; sequences of glacial, interglacial
and interstadial deposits; glaciofluvial landforms; records
of Holocene sea level changes in an area peripheral to the
main centre of isostatic uplift.
Beach and dune landforms; rock coast landforms in
granite
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the North East Coastal Plain are summarised in Table 9.2. However, there is
no systematic information on current impacts or trends.
Page 165
10 January, 2002
Table 9.2
Potential pressures and vulnerability of Earth heritage interests in the North East
Coastal Plain
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; river management
Vulnerable to drainage of bogs and peat extraction
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Generally robust to all but large scale developments such as
superquarries
Vulnerable to coast protection, recreation pressures,
commercial and industrial developments, land claim and sea
level rise
Vulnerable to ad hoc river engineering and management; river
engineering and management; afforestation gravel extraction;
land management changes
Vulnerable to land management changes, pollution
Palaeontological interests
Quaternary depositional landforms
and exposures
Palaeoenvironmental records
Records of sea level change
Rock coast features
Beaches and dunes
Fluvial geomorphology
Soils
8
•
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Fossils are collected from the fossiliferous exposures.
The unique pre-glacial gravels at Windy Hills are threatened by sand and gravel
extraction.
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1996) Coasts And
Seas Of The United Kingdom. Region 3. North-east Scotland: Cape Wrath to St Cyrus. Joint Nature
Conservation Committee, Peterborough
Clapperton, C.M. and Gemmell, A.M.D. (1998) Windy Hills SSSI, Aberdeenshire: site survey and
management phase 1. Scottish Natural Heritage Commissioned Report F98LF10 (Unpublished
report).
Cleal, C.J. and Thomas, B.A. (1995) Palaeozoic Palaeobotany of Great Britain. Geological Conservation
Review Series No. 9. Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Metcalf, S.J. (1999) Fossil Fishes of Great Britain. GCR Series No. 16., Joint Nature Conservation
Committee, Peterborough.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gemmell, A.M.D. and Stove, G.C. (1999) Windy Hills SSSI, Aberdeenshire: site survey and management
phase 2. Scottish Natural Heritage Commissioned Report F98LF11 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Page 166
10 January, 2002
Halcrow Crouch (1999) Aberdeen Bay Coastal Protection Study. Final Report. Unpublished report to
Aberdeen City Council, Scottish Natural Heritage and Grampian Enterprise. September 1999.
Aberdeen City Council, Aberdeen.
Hall, A.M. and Jarvis, J. (1995) A multiple till sequence near Ellon, Grampian Region: T.F. Jamieson’s
‘indigo boulder clay’ re-examined. Scottish Journal of Geology, 31, 53–59.
Hall, A.M., Duller, G., Jarvis, J. and Wintle, A.G. (1995) Middle Devensian ice-proximal gravels at Howe
of Byth, Grampian Region. Scottish Journal of Geology, 31, 61–64.
Office (Agriculture, Environment and Fisheries Dept.) and Historic Scotland. SNH RSM Report No. 144.
Battleby.
HR Wallingford (2000) Coastal Cells in Scotland. Cell 3 – Cairnbulg Point to Duncansby Head. Report to
Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and
Historic Scotland. SNH RSM Report No. 145. Battleby.
May, V. and Hansom, J.D. (in press). Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Peacock, J.D. and Merritt, J.W. (1997) Glacigenic rafting at Castle Hill, Gardenstown, and its significance
for the glacial history of northern Banffshire, Scotland. Journal of Quaternary Science, 12, 283–294.
Rafaelli, D. (1992) Conservation of Scottish Estuaries. Proceedings of the Royal Society of Edinburgh, 100B,
55–76.
Ritchie, W. (1992) Scottish Landform Examples – 4 Coastal Parabolic Dunes Of The Sands Of Forvie.
Scottish Geographical Magazine, 108, 39–44.
Ritchie, W., Smith, J.S. and Rose, N. (1978) The Beaches of North-east Scotland. Dept. of Geography,
University of Aberdeen. Countryside Commission for Scotland. Perth.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland, Methuen, London.
Smith, D.E., Firth, C.R., Brooks, C.L., Robinson, M. and Collins, P.E.F. (1999) Relative sea-level rise
during the Main Postglacial Transgression in NE Scotland, UK. Transactions of the Royal Society of
Edinburgh: Earth Sciences, 90, 1–27.
Stapleton, c. and Pethick, J. (1996) Coastal Processes and Management of Scottish estuaries. III. The Dee, Don
and Ythan Estuaries. Scottish Natural Heritage Review No. 52.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D. and Gould, D. (1995) British Regional Geology: The Grampian Highlands of Scotland (4th
edition). British Geological Survey. HMSO, London.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Whittington, G., Connell, R.E., Coope, G.R., Edwards, K.J., Hall, A.M., Hulme, P.D. and Jarvis, J. (1998)
Devensian organic interstadial deposits and ice sheet extent in Buchan, Scotland. Journal of Quaternary
Science, 13, 309–324.
Wright, J.S. (1997) Deep weathering profiles (saprolites) in north east Scotland. Scottish Geographical
Magazine, 113, 189–194.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 76, 77, 86, 87, 96, 97.
Soil Survey of Scotland Maps: 1:250,000 sheet 5 and colour 1:63,360 sheets 86, 87 and 77 cover Zone 9.
MLURI, Aberdeen.
Page 167
10 January, 2002
ZONE 10
1
•
•
•
•
•
•
2
CENTRAL HIGHLANDS
Highlights
Large outcrop areas of the Grampian Group within the Dalradian Supergroup.
Contains most of the Central Highland Migmatite Complex.
Key sites for Quaternary stratigraphy, including glacial, interglacial and interstadial
deposits.
Unique assemblage of features associated with formation of the Parallel Roads of
Lochaber ice-dammed lakes and their drainage.
Good representative examples of glacial and glaciofluvial deposits.
Excellent examples of river terraces, integrated drainage system, slot gorge and
discordant channel.
Geology
The zone is dominated by rocks of the Grampian Group, currently thought to represent the
lowermost stratigraphic portions of the Dalradian Supergroup. The Dalradian Supergroup
represents a thick (25 km) sequence of metasediments (metamorphosed sedimentary rocks)
and minor volcanics, bounded to the NW by the Great Glen Fault and to the SE by the
Highland Boundary Fault. They were deposited on a rifting continental margin. The rocks
eventually formed part of a mountain belt, formed as ‘Scotland’ collided with ‘England’ some
400 million years ago. Consequently, the rocks contain evidence of their history of
deposition, deformation and metamorphism.
The Dalradian Supergroup is divided into four groups: Grampian, Appin, Argyll and
Southern Upland Groups. The majority of Zone 10 comprises rocks belonging to the
Grampian Group; part of the Appin Group occurs in the south. Another aspect of the zone
is an area referred to as the Central Highland Migmatite Complex, centred upon
Inverbrough. Migmatites are rocks that have reached a position in the Earth’s crust where
they are at the point of melting. Consequently, they appear to represent a mixed rock of
metamorphosed sediment, containing streaks of granite-like material. Debate has
surrounded the true status of the migmatite complex, but in the meantime they are assigned
to the base of the Grampian Group. The migmatites comprise coarse-grained
metamorphosed sandstone, quartzites and pelites (metamorphosed mudstones). Any
sedimentary structures that from the time were laid down have been largely obliterated by
metamorphism and deformation. The main Grampian Group consists of metamorphosed
sandstones (psammites) and muddy sandstones (semi-pelites). The Appin Group comprises
slates, mica-schist and limestones.
As the deformation and metamorphism of the Dalradian Supergroup took place, partial
melting of rocks within the crust resulted in the formation of great masses of silica-rich melt
that moved upwards through the crust and became emplaced within the deformed and
metamorphosed Dalradian. The Monadliath granite is an example of one of these plutons.
It is noteworthy that the Grampian Group, in particular, has been the focus of much debate
owing to its compositional similarity to the Moine rocks of the Northwest Highlands. Being
the stratigraphic base of the Dalradian Supergroup, the Grampian Group is thought by some
to represent a southern extension of the Moine.
Page 168
10 January, 2002
3
Geomorphology
In the Central Highlands, glacial erosion has been less widespread than in the zones to the
north and west, the landscape is less fragmented and extensive remnants of pre-glacial
erosion surfaces dominate the landscape. Glacial erosion has been notably selective in its
effects and its imprint decreases towards the north and east. Where they occur, the glacial
troughs and corries stand in sharp contrast to the adjacent plateau surfaces, as around
Creag Meagaidh and the Carn Dearg Hills. Glacial deposits occur extensively on the lower
hillslopes and in the glens. Classic ‘hummocky’ moraines are associated with Loch Lomond
Readvance glaciers at Creag Meagaidh. Glaciofluvial deposits (outwash terraces, kame
terraces, eskers) are well developed along the Dulnain valley, in Strathdearn and along the
Findhorn valley. Among the highlights of the area are the Parallel Roads of Glen Roy and the
remarkable suite of features associated with the formation and drainage of the ice-dammed
lakes that formed in Glen Roy, Glen Gloy and Glean Spean during the Loch Lomond Stadial.
These features extend from the north end of Loch Treig to Fort Augustus (in Zone 7) and
include end moraines, lake shorelines, deltas, fans, cross-valley moraines and drainage
channels.
Periglacial features occur on the higher mountains. Among the more notable are boulder
lobes on Creag Meagaidh.
The vegetation history is known from a few sites mainly in the south of the area. During the
middle Holocene, oak and elm dominated the forests in the southernmost glens, but pine
predominated elsewhere.
The Central Highlands zone is generally mountainous with a high drainage density over the
Monadhliath Mountains, and short, steep mountain torrent headwater streams. These
streams undergo downstream channel development into braided or wandering gravel bed
streams before meandering in the middle and lower reaches (channel patterns that are
usually found downstream, outwith Zone 10). The fluvial resource of this area has been
altered by hydro schemes, with some lochs being dammed in the headwaters (e.g. Spey
Dam, Loch Laggan), and an aqueduct in Glen Truim.
The tributaries of the River Spey are important within this zone. The headwaters of the
Spey itself and its upland tributaries (e.g. the River Pattack and River Mashie) are braided or
wandering gravel bed rivers. However, moving downstream, the planform of the main stem
of the Spey downstream of Spey Dam becomes meandering in response to a reduced
channel gradient and there are only limited opportunities for channel division. The River
Dulnain is a major left bank tributary of the Spey, whose upper and middle reaches are
located within Zone 10. The River Dulnain is an active gravel bed river with an extensive
dendritic headwater system and a generally braided upper reach with an irregularly
meandering middle reach and a wide floodplain. Other dynamic left-bank tributaries of the
Spey found within Zone 10 include the River Calder.
The upper and middle reaches of the River Findhorn occur within this zone. The River
Findhorn is remarkable for having the highest recorded flow for any British river. It is an
upland wandering gravel bed river that begins as a steep mountain torrent but becomes
increasingly meandering downstream, where the gradient is reduced, before passing through
Randolphs Leap, one of the narrowest constricted bedrock reaches (or slot gorges) on a
major Scottish river. One of the Findhorn’s upland tributaries, Glen Mazeran, meanders
tortuously in a small alluvial basin. The Allt a’ Choire, a small south-bank tributary, is a
Page 169
10 January, 2002
notable example of an integrated drainage system. The River Findhorn also has a remarkable
suite of 13 terraces (the bottom ones are fluvially derived), which are located near the
Streens gorge. The Allt Mor (a headwater of the River Nairn) is notable for a hydraulic
discontinuity at the boundary between the steep upland tributary and the wide, flat valley of
the main stem. The upland tributaries of the River Nairn flow north-west before making an
abrupt right-angled turn to flow north-east. This may be related to headwater capture or to
the hydraulic discontinuity. This zone also contains the west-flowing River Spean and the
assemblage of fluvial features associated with the formation and drainage of the ice-dammed
lakes in Glen Roy, Glen Spean and Glen Gloy.
4
Soils
In general, soils in this region are formed on a wide variety of surface drift materials that are
predominantly acidic, coarse textured and have a low base status. This results in the most
common soil groups being podzols (39%), peats (29%) and montane soils (13%). This reflects
the changing texture of parent materials, a high moisture regime and low temperature,
which in places results in peat accumulation. At higher altitudes, alpine soils and lithosols
predominate and there are very few brown earths in this zone. Climate, topography and
parent materials have resulted in soils with low nutrient status and physical constraints,
which means that the soils have a low potential for cultivation. However, these soils do
support unique upland vegetation and constitute a major store of terrestrial carbon. Soils of
international significance are found on the Parallel Roads of Glen Roy, where extreme
textural changes occur over a small area, and alpine podzols found in the Monadliath
mountains are of national significance. The Monadliath mountains also have extensive areas
of severely eroded blanket peat (Grieve et al., 1994).
5
Summary of key Earth science features in the Central
Highlands
The principal Earth heritage interests in the Central Highlands are summarised in Table 10.1.
The Central Highlands includes a total of 12 GCR sites.
Table 10.1 GCR sites in the Central Highlands
GCR block
No. of sites
Principal interests
Dalradian
Quaternary of Scotland
4
4
Fluvial Geomorphology
4
Representative sections of the Dalradian Supergroup
Key sites for Quaternary stratigraphy (glacial,
interglacial and interstadial deposits); Parallel Roads of
Lochaber; representative site for Holocene vegetation
history and pine woodland history
Excellent examples of river terraces, integrated
drainage system, slot gorge and discordant channel
Page 170
10 January, 2002
6
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the Central Highlands are summarised in Table 10.2. However, there is no
systematic information on current impacts or trends.
Table 10.2 Potential pressures and vulnerability of Earth heritage interests in the Central Highlands
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction, infilling
of quarries
Vulnerable to mineral extraction/quarrying; commercial, industrial
and infrastructure developments; land management changes;
construction of tracks; afforestation; river management
Vulnerable to ad hoc river engineering and management; river
engineering and management; afforestation gravel extraction; land
management changes
Vulnerable to land management changes, pollution, peat erosion
Quaternary landforms
and deposits
Fluvial geomorphology
Soils
7
•
•
•
•
8
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Peat erosion is extensive across parts of the area.
Further erosion is a significant threat to peat deposits/soils across the area.
Afforestation and piecemeal development are threats to the Parallel Roads of Lochaber
Bibliography
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Gregory, K.J. (1997) Fluvial Geomorphology of Great Britain. Geological Conservation Review Series No.
13. Chapman and Hall, London.
Grieve, I.C., Hipkin, J.A. and Davidson, D.A. (1994) Soil Erosion Sensitivity in Upland Scotland. Scottish
Natural Heritage Research, Survey and Monitoring Report No. 24.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland, Methuen, London.
Stephenson, D. and Gould, D. (1995) British Regional Geology: The Grampian Highlands of Scotland (4th
edition). British Geological Survey. HMSO, London.
9
Maps
British Geological Survey Maps: 1:50,000 sheets: 63, 64, 73, 74, 84, 85.
Soil Survey of Scotland Maps: 1:250 000 sheet 5 and 1:50 000 uncoloured sheets 34, 35 and 26 cover
Zone 10. MLURI, Aberdeen.
Page 171
10 January, 2002
ZONE 11
1
•
•
•
•
•
•
•
•
•
•
•
•
•
2
CAIRNGORM MASSIF
Highlights
Large outcrop areas of the Grampian Group within the Dalradian Supergroup.
Cairngorm, Lochnagar and Glen Gairn granites.
Illustrations of Caledonian magmatic processes.
The location of the Forest Lodge section in Glen Tilt, described by James Hutton.
The occurrence of rare and unusual minerals such as topaz, chrysoberyl and columbite.
The occurrence of the semi-precious Cairngorm stones.
Metamorphic zones around granite plutons.
Exceptional assemblage of geomorphological features representing long-term mountain
landscape evolution.
Internationally important landscape of selective glacial erosion.
Nationally important assemblage of glacial and periglacial landforms, including landforms
of ice-sheet deglaciation and readvance and Loch Lomond Readvance glaciation.
Detailed records of Late-glacial and Holocene palaeoenvironmental change, including
records of pine forest history and history of arctic/alpine plant species.
Outstanding range of features of upland rivers, including mountain torrents, alluvial fans,
wandering gravel bed rivers, meanders and channel changes.
Alpine and iron podzols of national significance.
Geology
The Cairngorm Massif zone is dominated by rocks of the Dalradian Supergroup,
encompassing large masses of granite. The Dalradian rocks, which extend into neighbouring
Zones 10, 12, 13, 15 and 21 and further afield into Zones 6, 9 and 14, are predominantly
quartz-, feldspar- and mica-rich rocks, representing a metamorphosed and structurally
deformed pile of marine sediments and volcanic rocks, with a total thickness of around 25
km. Underlying more of the Scottish landscape than any other group of rocks, the Dalradian
is long established as a classic focus for the study of rock metamorphism (alteration by
intense heat and pressure) and deformation arising from continental collision.
Confined to the area defined by the Great Glen Fault to the NW and by the Highland
Boundary Fault to the SE, the Dalradian sediments and volcanics were originally laid down,
or in the case of the volcanics erupted onto, the southern margin of a continent referred to
by geologists as Laurasia, during the Precambrian and Cambrian periods between 700 million
and 600 million (and very possibly as recently as 500 million) years ago. The Laurasian
continent comprised North America, Greenland and the north-westernmost part of
present-day Scotland and was separated from what is now England and northern Europe by
the Iapetus Ocean.
As the sediments accumulated at the continental margin of Laurasia, the area subsided,
forming a basin into which the vast thickness of the Dalradian sedimentary and volcanic pile
accumulated; ongoing crustal instability as the basin formed gave rise to the volcanic activity.
As the basin developed and filled, over many millions of years, a variety of sediments,
including gritstones, sandstones, siltstones, mudstones, shales and limestones, were laid
down, reflecting variation, spatially and temporally, in the depositional environment. Much of
this reconstruction has been pieced together over many years of study since the late
nineteenth century, involving detailed mapping of the area. This work has also led to the
Page 172
10 January, 2002
division of the Dalradian into four parts: the Grampian, Appin, Argyll and Southern Highland
Groups, all four of which underlie the landscape of Zone 11.
In late Cambrian and through Ordovician times, the Dalradian Supergroup underwent
deformation and metamorphism as the Iapetus Ocean closed, with the continental collision
between Laurasia and a northern European continental landmass. This gave rise to the
eventual coming together of the crustal foundations that constitute Britain. On a large scale,
the collision gave rise to an alpine-scale mountain belt, termed the Caledonides, which is
represented structurally by large-scale folding within the rock layer sequences and a strong
NE–SW grain across the zone. Concurrently with the deformation, the various sedimentary
rocks were metamorphosed, with the recrystalisation of sandstones to quartzites, muddy
sands to pelites and mudstones to phyllites and slates.
As the deformation and metamorphism of the Dalradian Supergroup took place, partial
melting of rocks within the crust resulted in the formation of great masses of silica-rich melt
that moved upwards through the crust and became emplaced within the deformed and
metamorphosed Dalradian. The granites of Cairngorm, Glen Gairn, Lochnagar and Glen
Doll are examples of these plutons. Despite being Britain’s second largest single area of
granite, the Cairngorm granite has attracted relatively little geological research because of
its uniformity and the lack of exposures over much of the plateau. The Main Granite, which
forms the bulk of the Cairngorm pluton is a medium- to coarse-grained, variably porphyritic,
biotite–granite and mostly pink to red in colour. Grey or pink aplitic microgranites occur as
veins and larger lenses within the Main Granite. Fissures within the aplite veins have been
the main source of the semi-precious Cairngorm stones. The Loch Avon area is also a
nationally important locality for the occurrence of blue topaz and a rare suite of granite
accessory minerals (e.g. chrysoberyl and columbite).
The Caledonian plutons are also of significance for illustrating magmatic processes. At Red
Craig on the Glen Doll pluton, there is an important illustration of the interactions between
different magma types. Above Forest Lodge in Glen Tilt, at the edge of the Glen Tilt granite
complex, James Hutton in 1785 first found and documented field evidence to support his
theory that granite was an intrusive rock being emplaced into country rocks in a hot fluid
state. Hutton’s field evidence from Forest Lodge was crucial in the development of modern
geology, and the locality is therefore of international importance on historical grounds. Glen
Clova is nationally important for metamorphic zones in the surrounding Dalradian country
rocks associated with the granite intrusions.
It is noteworthy that as research continues on the granites, the host rocks are also receiving
attention. The Grampian Group, in particular, has been the focus of much debate owing to
its compositional similarity to the Moine rocks of the Northwest Highlands. Being the
stratigraphic base of the Dalradian Supergroup, the Grampian Group is thought by some to
represent a southern extension of the Moine assemblage, which occurs mostly to the north
of the Great Glen Fault.
3
Geomorphology
The Cairngorms include the largest area of highest ground in Britain. The core mountain
area comprises a series of ancient erosion surfaces, with the higher summits standing above
them. These surfaces support tors and pockets of deeply weathered bedrock. Juxtaposed
Page 173
10 January, 2002
with these features are spectacular landforms of glacial erosion, including troughs (Avon,
Einich), corries, glacially breached watersheds (Lairig Ghru, Lairig an Laoigh) and glacial
diversions of drainage (Feshie, Avon at Inchrory, Water of Caiplich, Tilt), indicating that
glacial erosion has been highly selective in its effects. The adjacent glens and straths support
a diverse assemblage of glacial meltwater features and glacial deposits, notably meltwater
channels, eskers, kames, kettle holes, terraces and moraines (e.g. Glen More, Glen Feshie,
Glen Avon, Glen Lui). On the northern flanks of the Cairngorms there is evidence for a
readvance/stillstand of the last ice sheet, and several corries contain excellent examples of
Loch Lomond Readvance moraines. Several rock slope failures are present, some associated
with fossil rock glaciers. Periglacial landforms are extensively developed on the higher slopes
and plateau surfaces. Postglacial and contemporary geomorphological processes are
particularly evident in river channel changes (e.g. Glen Feshie), slope erosion (e.g. Glen
Feshie, Lairig Ghru) and periglacial processes (montane zone). The Cairngorms form an area
of international importance for geomorphology.
The Lochnagar and Eastern Grampian mountains form an essentially similar landscape,
although the intensity of glacial erosion decreases eastwards and erosion surfaces become
more extensive. Glacial erosional landforms are well developed around Lochnagar and Glen
Clova. Glacial and glaciofluvial deposits are well represented in the glens, particularly Clova,
Esk and Callater. Lochnagar is also noted for its spectacular gelifluction lobes, and similar
features occur on Mount Keen. In Glen Clova, above Loch Brandy, there is a spectacular
incipient rock slope failure. The Ladder Hills and the hills to the NE show little evidence of
glacial modification, although they are relatively deeply dissected and include a number of
basins with deeply weathered bedrock (e.g. Cabrach).
To the southwest of the main Cairngorm mountain area, erosion surfaces again dominate
the landscape, and the Gaick area is noted for its occurrences of substantial thicknesses of
deeply weathered bedrock. Glacial erosion is localised along major drainage lines, watershed
breaches (e.g. Glen Tilt, Gaick, Pass of Drumochter) and shallow corries. Glacial deposits
add significantly to the topographic detail in many of the glens (e.g. Glen Truim, Glen Garry,
Glen Tromie and at Loch Etteridge). During the Loch Lomond Stadial, glaciers and icefields
produced many small-scale meltwater channels on the fringes of the Gaick plateau and welldeveloped hummocky moraines and terraces at Drumochter. Postglacial slope modification
is particularly well demonstrated at the Pass of Drumochter, where debris flows continue to
be active. The hills west of Drumochter are noted for their fine assemblage of periglacial
landforms, including solifluction features and ploughing boulders.
The vegetation history has been studied at a number of key sites in the area (e.g. Abernethy
Forest, Morrone, Coire Fee). During the middle Holocene, pine and birch forest
predominated. In some areas (Coire Fee, Morrone), certain arctic–alpine species have
survived throughout the Holocene in favourable habitats. At Inchrory in Glen Avon, a tufa
deposit has yielded a valuable record of environmental change during the last c.10,000 years.
Human impacts are evident from palaeolimnological studies, which show that the high corrie
lochs are contaminated by fly-ash particles and trace metals, and that some have undergone
significant acidification from atmospheric pollution over the last 100 years.
The Cairngorm Massif zone contains the headwaters of many of the main rivers of eastern
and north-eastern Scotland. Thus, there are fundamental links between this zone and Zones
9, 12, 15, 16 and 21, which contain the middle and lower reaches of these rivers .
Page 174
10 January, 2002
The Cairngorm Massif provides the headwaters for the two main east-flowing rivers of
north-east Scotland, the Dee and the Don. The Dee drains the southern side of the
Cairngorms, with many of the main tributaries occupying (and meandering through) flatbottomed glacial troughs and alluvial basins (e.g. Derry Burn in Glen Derry, River Dee
downstream from the Lairig Ghru). The Cairngorm Massif zone also contains the
headwaters of the River Muick, the Water of Feugh and the Clunie Water, which are
northerly flowing tributaries of the Dee. The headwaters of the Don are also in an alluvial
basin and meander tortuously in the upper reaches. Lochs and lochans only appear in the
extreme headwaters, and first-order tributaries feeding the main stem rivers are generally
short, steep mountain torrents with coarse bed material and alluvial fans at their base. The
main stems of the Dee and the Don in this zone are sinuous and gently meandering with
limited division. Bed material size (and origin) within the rivers varies markedly. This is a
function of the abundance of glacially derived material available for entrainment. The Derry
Burn occupies an alluvial basin (which is itself situated within a wider glacial trough) that has
developed as a result of the local base level control exerted by the presence of an outcrop
of resistant bedrock. The river is important for the tortuous, rectangular meander bends,
presence of cut-offs and former channels of varying age on the valley floor, and features
such as meander scrolls. The neighbouring catchment, the Luibeg Burn, has a much steeper
gradient, and the river provides a good example of a coarse-grained mountain torrent. Of
added interest is the persistence of features relating to floods in 1829 and 1956. The
confluence of the Quoich fan and the River Dee provides an excellent example of a large,
active, low-angle alluvial fan. The Quoich debouchs from a rock-controlled reach shortly
upstream of the confluence, making a rapid downstream transition but unfortunately has
been subject to engineering in the past. The drains in the area surrounding the Quoich Fan
have recently been blocked in an attempt to create a wetland environment.
The Cairngorm Massif also includes the headwaters of the River Avon, a major northflowing tributary of the Spey. In its upper reaches, the Avon is relatively confined with some
evidence of limited braiding and meandering. It has the characteristics of a typical Scottish
wandering gravel bed river, i.e. it has a changeable sinuous planform, which can also be seen
in the River Livet and the Dorback Burn, both of which are nearby north-flowing tributaries
of the Spey. The rectangular meanders of the Avon near Tomintoul are geologically
controlled. The right-angled bend at Inchrory is a glacial legacy (e.g. of headwater capture).
Like the Derry Burn, the Conglass Water provides a remarkable sequence of irregular
tortuous meanders in an upland (but very flat) environment and these meanders are
extremely stable and located within an extremely fertile basin that has developed through
the deposition of fine sediments during overbank flood events. The north-flowing Allt Mor
(River Druie) has been the subject of considerable research. It is an excellent example of a
coarse-grained mountain torrent that is relatively stable for the majority of the year but can
generate significant channel change in periods of intense localised rainfall over the summit of
the Cairngorm massif.
Glen Feshie is internationally famous for fluvial geomorphology, comprising one of the most
active braided river sections in Britain in the upper reaches, a wandering gravel bed river in
its middle reaches and a highly dynamic confluence fan at its confluence with the Spey. Each
section is important in a national context but together the suite of different river patterns,
which demonstrate downstream change in river behaviour, add up to the most important
fluvial geomorphology site in Scotland. The Feshie Fan has been subject to river engineering
in the recent past and the volumes of river gravels it deposits in the Spey were the cause of
great controversy which led to a Public Inquiry. However, the high rates of fluvial activity in
Page 175
10 January, 2002
the fan provide the river with an opportunity to restore its planform to a more natural state
during flood conditions.
The Cairngorm Massif zone also incorporates the headwaters of south-eastern-flowing
rivers such as the River Clova, Prosen Water and West Water. Within this zone these
rivers are small and steep with the characteristics of upland streams. The zone also contains
tributaries of the River Tay (the River Tilt and the River Garry), although the Tay itself rises
far to the west. The River Garry has been captured for hydro-electricity and has an
extremely low base flow for much of the year. The Garry is not the only river in this zone
that has been subject to modifications for hydro-electricity – the Tromie (a tributary of the
River Spey) is subject to inter-catchment water transfer. The Allt Dubhaig, a small tributary
of the River Garry, is one of the most intensively studied rivers in Britain. The controls on
river planform change downstream, generating a river system that shows a downstream
progression in channel pattern over a distance of approximately 3 km. The Allt Dubhaig has
been likened to an outdoor laboratory for fluvial studies.
4
Soils
The majority of the soils are podzols formed on coarse-textured acidic parent materials that
have been subject to intense leaching. Alpine/sub-alpine and montane soils are found at
altitudes above 500 m. In poorly drained areas, such as exposed summits and local
topographic basins, accumulation of organic matter results in peat formation, notably in the
extensive montane blanket mires on the Moine Mhor. Soil formation is retarded by
climate/topography, which results in the formation of unique soils (alpine podzols) that
sustain vegetation adapted to conditions on the massif. As plant growth is usually retarded,
organic matter content in these soils takes many years to accumulate, so that they are
especially sensitive and fragile. On steep slopes, soil erosion could be a problem if surface
vegetation is disturbed or removed, as subsoils are coarse textured and friable. On the high
plateaux there are close relationships between soils, geomorphology and plant habitats (e.g.
in relation to drainage, exposure and snow-lie patterns).
South and east of the Cairngorm Mountains, the Dalradian rocks form a varied group
dominated by quartz- and mica-rich rocks but with important outcrops of limestone (e.g. in
Deeside and along much of the A93 south of Braemar) and hornblende schists. Here, the
more diverse soil associations reflect the complexity of the underlying geology. For
example, brown forest and base-rich soils are developed on limestones and basic igneous
rocks; brown magnesium soils and magnesium gleys are developed on ultrabasic igneous
rocks such as serpentinites; rankers and lithosols are developed especially on quartzites and
granites. Peat is extensively developed on the plateau surfaces north of Glen Clova. The
iron podzols at Abernethy Forest are rare in Scotland, being formed under native
Caledonian pine forest.
5
Summary of key Earth science features in the Cairngorm
Massif
The principal Earth heritage interests in the Cairngorm Massif are summarised in Table 11.1.
The Cairngorm Massif includes a total of 28 GCR sites.
Page 176
10 January, 2002
Table 11.1 GCR sites in the Cairngorm Massif
GCR block
No. of sites
Principal interests
Dalradian
Caledonian Igneous
9
2
Mineralogy
Quaternary of Scotland
4
5
Fluvial Geomorphology
7
Tufa
1
Representative sections of the Dalradian Supergroup
Igneous rocks formed as a result of the Caledonian
Orogeny, important in understanding magmatic
processes
The occurrence rare and unusual minerals
Nationally and internationally important sites for
glacial geomorphology and mountain landscape
evolution; Late-glacial and Holocene vegetation
history and history of arctic–alpine species Abernethy
Forest
Sites representing the major features of upland rivers,
including mountain torrents, alluvial fans, wandering
gravel bed rivers, meanders and channel changes
Holocene environmental history
6
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the Cairngorm Massif are summarised in Table 11.2. However, there is no
systematic information on current impacts or trends.
Table 11.2 Potential pressures and vulnerability of Earth heritage interests in the Cairngorm Massif
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction, infilling of quarries
Vulnerable to irresponsible large-scale collecting
Generally robust
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure
developments; land management changes; construction of
tracks; afforestation; river management
Vulnerable to enhanced erosion through overgrazing and
increased recreational pressures
Vulnerable to drainage of bogs and peat extraction
Vulnerable to river management, climate change, gravel
extraction and changes in land use management
Vulnerable to land management changes, pollution, peat
erosion
Mineralogical interests
Large-scale glacial and other landforms
Quaternary depositional landforms
and exposures
Periglacial geomorphology
Palaeoenvironmental records
River geomorphology
Soils
7
•
•
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
In some areas, commercial afforestation has obscured landform assemblages, as in Glen
More, lower Glen Feshie and Glen Clova.
Page 177
10 January, 2002
•
•
•
•
•
•
•
•
•
•
8
Footpath erosion has had localised impacts on periglacial features on the higher slopes
and plateaux of the Cairngorms.
Overgrazing is locally affecting slope stability and erosion in Glen Feshie.
Truncation of alpine podzol profiles on the high plateau provides evidence of soil
erosion, but it is unclear to what extent this reflects current processes or processes in
the recent past.
Peat erosion is extensive on blanket bog surfaces across the area.
Modifications have been made to many river channels (notably Allt Mor, Feshie
confluence, Quoich fan) and to river discharges (Garry).
High deer numbers and the reduction in the vegetation cover through overgrazing has,
in places, added to the instability of upland channels.
Soil changes are likely to follow regeneration of natural woodland.
There are potential threats from climate change and atmospheric pollution to periglacial
process activity and soils on the plateau, both through direct changes in processes (frost,
wind, water) and through possible changes in vegetation cover.
The river systems of the Cairngorms are generally under less threat from river
engineering than rivers in other parts of the country. However, the major tributaries of
the River Spey are subject to some engineering, mainly for fishery management
purposes.
Further erosion is a significant threat to peat deposits/soils across the area.
Bibliography
Anderson, H.A., Gauld, J.H. and Stewart, M. (1997) Pilot study of soils within the Cairngorm Ski area.
Scottish Natural Heritage Commissioned Report F97AC101 (Unpublished report).
Battarbee, R.W., Jones, V.J., Flower, R.J., Appleby, P.G., Rose, N.L. and Rippey, B. (1996)
Palaeolimnological evidence for the atmospheric contamination and acidification of high Cairngorm
lochs, with special reference to Lochnagar. Botanical Journal of Scotland, 48, 79–87.
Brazier, V., Gordon, J.E., Hubbard, A., and Sugden, D.E. (1996) The geomorphological evolution of a
dynamic landscape: the Cairngorm Mountains, Scotland. Botanical Journal of Scotland, 48, 13–30.
Glasser, N.F. and Bennett, M.R. (eds) 1996. The Quaternary of the Cairngorms. Field Guide. Quaternary
Research Association, London.
Chapman, S.J. and Campbell, C.D. (1999) Effects of native woodland expansion on soil carbon balance,
Abernethy Forest. Scottish Natural Heritage Commissioned Report F98AC103 (Unpublished
report).
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Gordon, J.E., Thompson, D.B.A., Haynes, V.M., Brazier V. and MacDonald, R. (1998) Environmental
sensitivity and conservation management in the Cairngorm Mountains, Scotland. Ambio, 27, 335–344.
Gregory, K.J. (1997) Fluvial Geomorphology of Great Britain. Geological Conservation Review Series No.
13. Chapman and Hall, London.
Haynes, V.M. and Grieve, I.C. (2000) Baseline survey for monitoring geomorphological and soil changes
on the Braeriach/Einich Cairn Plateau. Scottish Natural Heritage Commissioned Report I001440
(Unpublished report).
Haynes, V.M., Grieve, I.C., Price-Thomas, P. and Salt, K. (1998) The geomorphological sensitivity of the
Cairngorm high plateaux. Scottish Natural Heritage Research, Survey and Monitoring Report No. 66.
Jones, V.J., Flower, R.J., Appleby, P.G., Natkanski, J., Richardson, N., Rippey, B., Stevenson, A.C. and
Battarbee, R.W. (1993). Palaeolimnological evidence for the acidification and atmospheric
contamination of lochs in the Cairngorm and Lochnagar areas of Scotland. Journal of Ecology, 81, 3–24.
Page 178
10 January, 2002
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland, Methuen, London.
Stephenson, D. and Gould, D. (1995) British Regional Geology: The Grampian Highlands of Scotland (fourth
edition). British Geological Survey. HMSO, London.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Werritty, A., Hoey, T. and Black, A. (1999) Geomorphological and hydrological changes at the River
Feshie/Spey confluence and Insh Marshes SSSI. Scottish Natural Heritage Commissioned Report
F98AC101 (Unpublished report).
Wilson, B. (1998) Pinewood soils in the RSPB Abernethy Forest Reserve. Scottish Natural Heritage
Commissioned Report F97AC102 (Unpublished report).
Werritty, A. and Brazier, V. (1991) The Geomorphology, Conservation and Management of the River Feshie
SSSI. Report for the Nature Conservancy Council, Peterborough.
9
Maps
British Geological Survey Maps: 1:50,000 sheets 63, 64, 65, 74, 75, 76, 85, 86, 95.
Soil Survey of Scotland Maps: 1:250,000 sheet 5 encompasses Zone 11 and uncoloured 1:50,000 sheets
36, 43 and 44 cover some of the Cairngorm Massif area. MLURI, Aberdeen.
Page 179
10 January, 2002
ZONE 12
1
•
•
•
•
•
•
•
2
NORTH-EAST GLENS
Highlights
The Dalradian Supergroup.
Illustrations of Caledonian magmatic processes in ultrabasic intrusions.
Devonian sedimentary sequences.
Assemblage of geomorphological features representing long-term upland landscape
evolution.
Good assemblage of glacial landforms, including landforms of selective glacial erosion,
ice-sheet deglaciation and Loch Lomond Readvance glaciation.
Detailed records of Late-glacial and Holocene palaeoenvironmental change, including
records of woodland history and human impacts on the landscape.
Excellent example of outwash terraces and palaeochannels
Geology
The North East Glens zone is entirely dominated by rocks of the Dalradian Supergroup,
which extend into neighbouring Zones 9, 10, 11 and 21 and further afield into Zones 6, 13,
14 and 15. Predominantly quartz-, feldspar- and mica-rich, the rocks of Zone 12 represent a
metamorphosed and structurally deformed pile of marine sediments and volcanic rocks,
with a total thickness of around 25 km. Underlying more of the Scottish landscape than any
other group of rocks, the Dalradian is long established as a classic focus for the study of
rock metamorphism (alteration by intense heat and pressure) and deformation arising from
continental collision.
Confined to the area defined by the Great Glen Fault to the NW and by the Highland
Boundary Fault to the SE, the Dalradian sediments and volcanics were originally laid down
on, or in the case of the volcanics erupted onto, the southern margin of a continent
referred to by geologists as Laurasia, during the Precambrian and Cambrian periods between
700 and 600 million (and very possibly as recent as 500 million) years ago. The Laurasian
continent comprised North America, Greenland and the north-westernmost part of
present-day Scotland and was separated from what is now England and northern Europe by
the Iapetus Ocean.
As the sediments accumulated at the continental margin of Laurasia, the area subsided
forming a basin into which the vast thickness of the Dalradian sedimentary and volcanic pile
accumulated; ongoing crustal instability as the basin formed gave rise to the volcanic activity.
As the basin developed and filled, over many millions of years, a variety of sediments,
including gritstones, sandstones, siltstones, mudstones, shales and limestones, were laid
down, reflecting variation, spatially and temporally, in the environment. Much of this
reconstruction has been pieced together over many years of study since the late nineteenth
century, involving detailed mapping of the area. This work has also led to the division of the
Dalradian into four parts: the Grampian, Appin, Argyll and Southern Highland Groups. The
Argyll Group underlies most of Zone 12 east of Dufftown, rocks of the Appin and Southern
Highland Group also occur, but are of a less real extent. In the western extension of the
zone, south-west of Dufftown towards Kingussie, rocks of the Grampian Group underlie
the landscape.
Page 180
10 January, 2002
In late Cambrian and through Ordovician times, the Dalradian Supergroup underwent
deformation and metamorphism as the Iapetus Ocean closed, with the continental collision
between Laurasia and a northern European continental landmass. This gave rise to the
eventual coming together of the crustal foundations that constitute Britain. On a large scale,
the collision gave rise to an alpine-scale mountain belt, termed the Caledonides, which
structurally is represented by large-scale folding within the rock layer sequences and a
strong NE–SW grain across the zone. Concurrently with the deformation, the various
sedimentary rocks were metamorphosed, with the recrystalisation of sandstones to
quartzites, muddy sands to pelites and mudstones to phyllites and slates.
Of all the zones that are underlain by rocks of the Dalradian Supergroup, Zone 12 contains
the most intensely metamorphosed. The rocks in places contain the mineral sillimanite,
derived when a mudstone or shale is exposed to temperatures and pressures in excess of
500°C and 4 kb. In places the rocks have been metamorphosed to such a high grade that
they were close to melting point and show evidence of having behaved as a plastic during
deformation, for example in the southern part of the zone between Lochnagar and
Pitlochry. These high-grade metamorphic rocks are known as migmatites.
The actual partial melting of rocks within the crust, as the deformation and metamorphism
of the Dalradian Supergroup took place, resulted in the formation of great masses of silicarich melt that moved upward through the crust and became emplaced within the deformed
and metamorphosed Dalradian. The granites of Lochnagar, Bennachie and Balblair are
examples of these plutons. In contrast to the granites, the zone encompasses other major
intrusions of basic and ultrabasic character. These bodies of rock, such as the
Morven–Cabrach and Huntly intrusions, are formed from silica-poor, base-rich magma.
Study of the Huntly intrusion at Bin Quarry, which shows troctolitic and gabbroic
cumulates, provides evidence of gravity accumulation of crystals.
In the north of the zone around Lumsden and east of Fochabers, there are outcrops of
Devonian rock that date from approximately 400 million and 370 million years ago
respectively. These Lower and Middle Devonian rocks represent river sands and silts that
were deposited upon the Dalradian by rivers that were eroding the newly formed
Caledonides mountain chain. At Rhynie the Devonian is totally surrounded by Dalradian
rock forming an inlier, suggesting a basin of deposition actually developed high within the
Caledonide mountains. In both cases the Devonian rock rests with an unconformity above
the Dalradian.
The southern part of this zone is delineated in part by the Highland Boundary Fault, a major
break in the crust of Scotland which separates the Midland Valley from the Highlands.
Formed as the crustal fragment that underlies Scotland and the rest of Britain came
together during the formation of the Caledonide mountains, the fault is still the source of
earthquake activity in this zone today.
3
Palaeontology
Cambrian and Ordovician sedimentary rocks within the Highland Border Complex, along
the southern margin of the zone, yield a rare but important marine shelly fauna that has
been crucial in elucidating ancient palaeogeographies and the evolution of Scotland’s
foundations.
Page 181
10 January, 2002
4
Geomorphology
The hills of the Grampian fringe have been relatively little modified by glacial erosion and
generally have broad, rounded outlines that often show general accordances of summit
levels associated with dissected pre-glacial erosion surfaces. Locally, adjacent to major lines
of ice discharge from the Highland ice sheets, glacial erosion is more marked, as along parts
of the Dee valley and adjacent uplands. The upland areas are separated by ice-deepened
glens and topographic basins, as at Glen More and Alford, which reflect differential erosion
during pre-glacial times. The hillslopes are frequently covered in solifluction debris, and the
floors of the glens infilled with till and glaciofluvial deposits, as in Strath Spey (notably at
Loch Etteridge), along the Dee (notably at Muir of Dinnet), near Rhynie and in Glen Clova
and Glen Esk. These deposits are often reworked to form river terraces.
The vegetation history is documented at a few sites. During the middle Holocene, the lower
glens were occupied by birch–hazel–oak woodland, with pine and birch in the more western
parts. Sites in the Muir of Dinnet area provide important records of human impacts on the
landscape.
The North East Glens contain the middle reaches of the Spey, Don and Dee, major rivers
that drain to the north and east, and they also contain the upper reaches of the northwardsmeandering Deveron and its meandering tributary, the Borgie. The low gradient of the
coastal plain means that the upper and middle reaches of the Dee are sinuous with some
rectangular bends, whereas the upper and middle reaches of the Don are more meandering.
In contrast, north-east-flowing tributaries of the Dee, such as the Tanar and the Muick,
drain the northern slopes of the Grampian Mountains, and the steep catchments generate
dynamic wandering gravel bed streams. These tributaries may impact on the planform of the
main stem of the Dee downstream of the confluence by locally increasing the volume of
large sediment that is available within the stream bed. The Feugh is an unusual south-bank
tributary of the Dee, because it meanders irregularly in a course parallel to that of the Dee
before their confluence. The River Spey also becomes increasingly sinuous downstream
within this zone, with the middle reaches meandering across a wide floodplain, although the
sediment load remains gravel- and cobble-sized. The dynamic nature of the Spey over time
is apparent from the palaeochannels on the floodplain around Newtonmore.
Rivers draining south from the Grampian Mountains are also dynamic, and the zone contains
the middle reaches of the North Esk and its tributary the West Water, which are both
heavily influenced by extensive glacial deposition in the area (which alters sediment
availability in the catchment) and the existence of palaeochannels and terraces. The
extensive suite of terraces and palaeochannels in this area is particularly notable. The middle
reaches of the River Clova, River Prosen and River Ardle are all within this zone and are
generally meandering, as is the south-draining River Isla and its tributary the Ericht, which
have some rectangular meanders. The tendency of the Isla to flood has resulted in its being
embanked in parts.
5
Soils
In this zone the solid geology is blanketed by drift up to 10 m thick, but this drift is thickest
in valley bottoms, and may be absent on hill-tops. Thus, soil types are varied, often as a
function of the underlying parent materials. Commonly, gabbro hills give base-rich soils with
pH values around neutral, whereas those of granite give nutrient-poor, acid soils. Most of
Page 182
10 January, 2002
the drift materials upon which soils have formed are coarse-grained and base-deficient,
resulting in a large number and variety of podzols, which make up 68% of the soils in this
zone. Organic matter accumulation occurs where cool, wet conditions prevail upslope, and
many soils contain a significant peaty horizon. Soils of national significance include those
formed on basic and ultrabasic drift material (brown magnesian and calcareous soils) and
alpine soils on Hill of Morven.
6
•
Summary of key Earth science features in the North East
Glens
The principal Earth heritage interests in the North East Glens are summarised in Table
12.1. The North East Glens includes a total of 7 GCR sites.
Table 12.1 GCR sites in the North East Glens
GCR block
No. of sites
Principal interests
Caledonian Igneous
2
Mineralogy
Quaternary of Scotland
1
3
Fluvial Geomorphology
1
Igneous rocks formed as a result of the Caledonian
Orogeny
Unusual and rare minerals
Excellent assemblages of ice-sheet deglaciation
landforms and Late-glacial and Holocene
palaeoenvironmental records
Excellent example of outwash terraces and
palaeochannels
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the North East Glens are summarised in Table 12.2. However, there is no
systematic information on current impacts or trends.
Table 12.2 Potential pressures and vulnerability of Earth heritage interests in the North East Glens
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Palaeontological interests
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Quaternary depositional landforms Vulnerable to mineral extraction/quarrying; commercial,
and exposures
industrial and infrastructure developments; land
management changes; construction of tracks; afforestation; river
management
Palaeoenvironmental records
Vulnerable to drainage of bogs and peat extraction
River geomorphology
Vulnerable to river management, climate change, gravel
extraction and changes in land use management
Soils
Vulnerable to land management changes, pollution and peat
erosion
Page 183
10 January, 2002
8
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Bibliography
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Gregory, K.J. (1997) Fluvial Geomorphology of Great Britain. Geological Conservation Review Series No.
13. Chapman and Hall, London.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland, Methuen, London.
Stephenson, D. and Gould, D. (1995) British Regional Geology: The Grampian Highlands of Scotland (fourth
edition). British Geological Survey. HMSO, London.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 55, 56, 64, 65, 66, 75, 85, 95.
Soil Survey of Scotland Maps: 1:250,000 sheet 5 encompasses Zone 12 and coloured 1:63,360 sheets 76
and 86 cover some of the N.E. Glens. MLURI, Aberdeen.
Page 184
10 January, 2002
ZONE 13
1
•
•
•
•
•
•
•
•
•
•
•
2
LOCHABER
Highlights
Dalradian Supergroup metamorphic rocks and structures.
Internationally important example of multiple pulse pluton emplacement at Loch Etive.
A classic example of cauldron subsidence at Glen Coe.
Largest zone of lead–zinc ore mineralisation in Scotland.
Only known occurrence in the world of the cadmium-rich variety of the mineral
tetrahedrite.
Landscapes of glacial erosion, notable for troughs and watershed breaching
Assemblage of landforms related to Loch Lomond Readvance glaciation and deglaciation,
including periglacial trimlines.
Unique assemblage of features associated with formation of the Parallel Roads of
Lochaber ice-dammed lakes and their drainage.
The rock slope failure of the ‘Lost Valley’.
Records of Late-glacial and Holocene palaeoenvironmental change from Rannoch Moor.
Montane soils, rankers and lithosols of national significance on slopes and summits.
Geology
Lochaber is entirely dominated by rocks of the Dalradian Supergroup, which extend into
neighbouring Zones 14, 15,11,10 and further afield into zones 6, 9, 12 and 21.
Predominantly quartz-, feldspar- and mica-rich, the rocks of Zone 13 represent a
metamorphosed and structurally deformed pile of marine sediments and volcanic rocks,
with a total thickness of approximately 25 km. Underlying more of the Scottish landscape
than any other group of rocks, the Dalradian Supergroup is long established as a classic
focus for the study of rock metamorphism (alteration by intense heat and pressure) and
deformation arising from continental collision.
Confined to the area defined by the Great Glen Fault to the NW and by the Highland
Boundary Fault to the SE, the Dalradian sediments and volcanics were originally laid down
on, or in the case of the volcanics erupted onto, the southern margin of a continent
referred to by geologists as Laurasia, during the Precambrian and Cambrian periods between
700 and 600 million (and very possibly as little as 500 million) years ago. The Laurasian
continent comprised North America, Greenland and the north-westernmost part of
present-day Scotland and was separated from what is now England and northern Europe by
the Iapetus Ocean.
As the sediments accumulated at the continental margin of Laurasia, the area subsided
forming a basin into which the vast thickness of the Dalradian sedimentary and volcanic pile
accumulated; ongoing crustal instability as the basin formed gave rise to the volcanic activity.
As the basin developed and filled, over many millions of years, a variety of sediments,
including gritstones, sandstones, siltstones, mudstones, shales and limestones, were laid
down, reflecting variation spatially and temporally in the environment. Much of this
reconstruction has been pieced together over many years of study since the late nineteenth
century, involving detailed mapping of the area. This work has also led to the division of the
Dalradian into four groups: Grampian, Appin, Argyll and Southern Highland Groups. The
majority of Zone 13 comprises rocks belonging to the Grampian and Appin Groups, with
Page 185
10 January, 2002
parts of the Argyll Group in the westernmost tip of the zone and a small part of the
Southern Highland Group in the south-east in the vicinity of Crianlarich.
In late Cambrian and through Ordovician times, the Dalradian Supergroup underwent
deformation and metamorphism as the Iapetus Ocean closed as a result of the continental
collision between Laurasia and a northern European continental landmass. This gave rise to
the eventual coming together of the crustal foundations that constitute Britain. On a large
scale the collision gave rise to an alpine-scale mountain belt, termed the Caledonides, which
structurally is represented by large-scale folding within the rock layer sequences and a
strong NE–SW grain across the zone. Concurrently with the deformation, the various
sedimentary rocks were metamorphosed, with the recrystalisation of sandstones to
quartzites, muddy sands to pelites and mudstones to phyllites and slates.
Partial melting of rocks within the crust, as the deformation and metamorphism of the
Dalradian Supergroup took place, resulted in the formation of great masses (plutons) of
silica-rich melt that moved upward through the crust and became emplaced within the
deformed and metamorphosed Dalradian. The granites of Loch Etive, Cruachan and
Rannoch Moor, which underlie a significant portion of Zone 13, are examples of these
plutons. The Etive pluton, which is elliptical in shape and covers an area of 300 km2, is of
national and international importance for illustrating various magma types and multiple pulse
emplacement.
After the formation of the Caledonian mountains, and during the time they were being
actively eroded, volcanism during Lower Devonian times approximately 400 million years
ago produced the volcanic complexes at Ben Nevis and Glencoe. Both complexes are
considered to be classic examples of the process called cauldron subsidence. This process
occurs when a particularly violent volcanic eruption removes large amounts of magma from
the magma chamber below the volcano. With the pressure from below removed, lavas
which form the surface expression of the volcano sink down into the magma chamber
below, producing a caldera like the modern-day Crater Lake in the western USA.
At Ben Nevis, a block of relatively homogeneous lava forms the summit and the great north
face of the mountain. This is surrounded by granitic rocks that crystallised within the magma
chamber into which the lava block sank. At Glen Coe, by contrast, the mountains are chiefly
made up of a sequence of lavas, and the granitic rocks which crystallised around them in the
magma chamber are more restricted. Of particular interest are exposures of the Ring Fault
(the fracture in the Earth’s crust down which the lavas sank), which can be seen at Stob
Mhic Mhartuin, above the eastern end of Glen Coe.
In the vicinity of Tyndrum is the largest zone of lead–zinc ore mineralisation in Scotland and
the only known locality in the world where the cadmium-rich variety of the mineral
tetrahedrite can be found. For over 120 years in the eighteenth and nineteenth centuries and
between 1916 and 1925, around 20,000 tons of high-grade lead–zinc ore was removed from
the Main Mine. The mineralisation occurs within NE–SW-running veins that corresponds to
a fault within the metamorphic Dalradian Supergroup, between rocks of the Grampian and
Argyll Groups. Although the faulting took place at a late stage in the deformation of the
Supergroup, the mineralisation along the fault line took place over 100 million years later
during the Carboniferous Period. Crustal instability at that time super-heated crustal fluids
to between 140o and 250oC. The circulating fluids leached minerals from rocks lower in the
crust and following percolation up through the fault line mineralisation of the metaliferous
Page 186
10 January, 2002
deposits took place. Although lead and zinc ore predominates, uranium ore and gold have
also been recovered from the mineral veins.
3
Geomorphology
The mountains of this zone are heavily dissected and ice scoured. The western glens are
heavily deepened and continue seawards as fjords where their lower reaches have been
drowned. There are a number of spectacular glacial troughs (e.g. Glen Coe) and glacial
breaches (e.g. Glen Coe, Lairig Gartain and Glen Etive). Hanging valleys are particularly well
developed as in the ‘Lost Valley’ in Glen Coe and upper Glen Nevis. Other notable features
of glacial erosion are the many corries, rock steps and superb ice-moulded bedrock forms
and roches moutonnées (particularly in lower Glen Nevis at Polldubh). The intensity of
glacial erosion decreases towards the NE, and in the Ben Alder area more extensive areas
of plateau surface are preserved; the latter area with its juxtaposition of plateau surfaces,
corries and glacial troughs is geomorphologically more similar to Zone 11. Rannoch Moor is
a good example of a high-level basin developed on granite less resistant than the rocks of
the surrounding mountains. This area formed an important centre for ice accumulation and
dispersion during the ice ages and this is reflected in the radial pattern of glacial troughs
spanning out from the basin (e.g. Treig and Ericht to the NE). Frost-weathered detritus is
common on the mountain tops, and in places there are examples of periglacial trimlines
marking the upper limits of the Loch Lomond Readvance glaciers. Many steeper slopes are
prone to debris flow activity with some of the finest examples in Scotland located in
Glencoe. The Lost Valley is dammed by a large rockslide of national importance.
There is a variable cover of drift on the lower slopes of the mountains and in the glens. This
may appear as a rather featureless spread of till (boulder clay), but in many areas there are
clear constructional features in the form of a variety of moraine ridges and mounds
associated with the Loch Lomond Readvance. ‘Hummocky’ moraines are superbly
developed on Rannoch Moor, end moraines at the north end of Loch Treig associated with
the Spean and Ossian glaciers and cross-valley moraines associated with the recession of the
Spean glacier around Spean Bridge and near Torlundy. Glacial outwash features are also well
developed as lacustrine and marine deltas. The former most notably at the north end of
Loch Treig, the latter at Corran and Ballachulish. The zone also includes part of the
assemblage of features associated with the Parallel Roads of Lochaber in Glen Spean (lake
shorelines, river terraces) and there are additional ice-dammed lake shorelines NE of Loch
Tulla. The pattern of decay of the readvance glaciers suggests recession of the ice towards
Rannoch Moor, and the basal sediments in enclosed basins in this area have an important
role in establishing early postglacial environmental conditions, plant colonisation patterns
and habitat development. These basal sediments are also important in dating the final
disappearance of the readvance glaciers.
The vegetation history of the area has been investigated at several sites, ranging from
Rannoch Moor in the west to the Monadliath Mountains in the east. The pollen records
show the early postglacial expansion of birch followed by the later arrival of other tree
species. Pine and birch formed the main elements of the woodland cover during the middle
Holocene. The upland area around the Allt na Feithe Sheilich on the eastern Monadliath
plateau contains one of the oldest blanket peat profiles in Britain.
Page 187
10 January, 2002
Zone 13 contains only a few short lengths of coastline, encompassing the heads and inner,
sheltered shores of Lochs Leven, Creran and Etive. The shorelines concerned are
dominated by gravels worked out of adjacent till deposits along with sporadic patches of
mud, sand and, at the loch heads, saltmarsh. Lochs Creran and Etive are typically deeper
here than at their entrances farther west (in Zone 14), reflecting glacial scouring and
deepening during past ice ages. The entrance to Loch Leven at Ballachulish is, in contrast,
constricted by an extensive shingle spread. Although forming part of the contemporary
shoreline, this landform is, however, related to glacial outwash processes during the Loch
Lomond Readvance rather than present-day marine activity.
The Lochaber zone straddles the main east–west watershed, and although the majority of
rivers within the zone drain west the zone also contains the headwater tributaries of the
easterly flowing Lyon and Dochart systems, much of the Rannoch Moor drainage system
and the headwaters of the River Falloch, which drains south into Loch Lomond. The easterly
flowing rivers have a smaller gradient than those flowing west, and, in consequence, channel
patterns contrast strongly on either side of the drainage divide, with a number of lochs and
lochans and irregularly meandering tributaries within the easterly flowing River Gaur and
Loch Rannoch system. In contrast, the high gradient of westerly flowing rivers precludes the
development of wide floodplains and meandering streams, and ensures that streams remain
dynamic and have gravel beds at their marine limits. The steep mountainous terrain and the
shallow soils help to generate a quick or flashy catchment response to rainfall on westerndraining rivers. This contrasts with the damped response on eastern rivers as a result of
storage within lochs and bogs and the more gentle gradient. The well-developed floodplain
of the River Spean just below Laggan Dam has allowed the stream to assume a more
sinuous course than occurs further downstream where the river is more constrained by the
valley sides.
The River Falloch drains into Loch Lomond and has a number of upland tributaries forming
a dendritic drainage system. Both the main stem and a number of the upland tributaries have
waterfalls in their lower reaches, indicating that they have not fully adjusted to the effects of
glaciation. The downstream tributary of the River Leven (the Allt na h-Eilde) has a waterfall
near the confluence with the Leven, and again this indicates that system response to baselevel changes over the Holocene has been slow.
The Rivers Etive, Tulla, Orchy and Nevis change downstream from upland mountain
streams into low sinuosity wandering gravel bed rivers. All display some braiding in their
middle or lower reaches. Bluck monitored the naturally dynamic channel pattern of the
Tulla (using oblique fixed-point photography) for many years, but engineering of the channel
destroyed the monitoring site. In contrast, the River Kiachnish is deeply incised along its
entire length and displays no downstream planform change, whereas the upper River Coe is
incised into bedrock, but downstream it displays significant channel planform change. The
Allt Coire Gabhail (or Lost Valley), a tributary of the River Coe, is an alluvial basin sealed by
a catastrophic rockfall, and here the gradual infilling of the alluvial basin has produced a
concave long profile and rapid downstream fining. The upper reaches of the River Creran
also appear to be in an alluvial basin, with a wide floodplain and a meandering channel
planform. The River Creran drains through a loch in its lower reaches (upstream of its
confluence with the sea loch), which is unusual in the local context.
Allt Coire Chailean (in Glen Orchy) is an integrated channel system and displays a range of
channel planforms over a short distance. Eas na Broige (in Glen Etive) is a debris cone
Page 188
10 January, 2002
where the sediments display successive phases of debris flow activity and alluvial fan
development.
4
Soils
The soils of this zone are formed predominantly on coarse-grained, acidic rocks and drift
material, and in valley bottoms deep morainic deposits make up the majority of soil-forming
materials. High rainfall, cool temperatures and acidic parent materials result in the
widespread occurrence of podzols in this zone. There is an altitudinal sequence where,
upslope, podzols give way to montane soils and alpine podzols on/near the summits. Where
topography and/or parent materials inhibit leaching, surface-water gleys predominate at
lower elevations and organic matter accumulation occurs. Over 43% of soils in this zone are
podzols and 26% are surface-water gleys, resulting in soils containing substantial reserves of
soil organic matter. The alpine soils found on the highest summits support unique montane
vegetation. Soils with national significance include lithosols on the Ben Nevis massif, rankers
on the steep slopes of Glencoe, alpine podzols on high summits and areas of hagged peat
within Rannoch Moor.
5
Summary of key Earth science features in Lochaber
The principal Earth heritage interests in Lochaber are summarised in Table 13.1. Lochaber
includes a total of 28 GCR sites.
Table 13.1 GCR sites in Lochaber
GCR block
No. of sites
Principal interests
Dalradian
12
Caledonian Igneous
8
Mineralogy
Quaternary of Scotland
1
2
Fluvial Geomorphology
4
Mass Movement
1
Representative sections of the Dalradian
Supergroup
Igneous rocks formed as a result of the Caledonian
Orogeny, important in understanding magmatic
processes
Important mineralisation
Internationally important features associated with
formation of the Parallel Roads of Lochaber ice
dammed lakes and their drainage; Late-glacial and
Holocene vegetation history of Rannoch Moor
Excellent examples of integrated fluvial systems,
debris flows and features associated with formation
of the Parallel Roads of Lochaber ice-dammed lakes
and their drainage
Rock slope failure in the Lost Valley
6
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in Lochaber are summarised in Table 13.2. However, there is no systematic
information on current impacts or trends.
Page 189
10 January, 2002
Table 13.2 Potential pressures and vulnerability of Earth heritage interests in Lochaber
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Generally robust
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; river management
Vulnerable to afforestation
Vulnerable to drainage of bogs and peat extraction
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Vulnerable to river management, climate change, gravel
extraction and changes in land use management
Vulnerable to land management changes, pollution, peat
erosion
Landforms of glacial erosion
Quaternary depositional landforms
and exposures
Periglacial trimlines
Palaeoenvironmental records
Modern and raised coastal features
River geomorphology
Soils
7
•
•
8
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Minerals are collected from the Tyndrum mine dump.
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Region 14. South-west Scotland: Ballantrae to Mull. Joint Nature
Conservation Committee, Peterborough
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Gregory, K.J. (1997) Fluvial Geomorphology of Great Britain. Geological Conservation Review Series No.
13. Chapman and Hall, London.
HR Wallingford (2000) Coastal Cells in Scotland. Cell 5- Cape Wrath to Mull of Kintyre. Report to Scottish
Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and Historic
Scotland. SNH RSM Report No. 147. Battleby.
May, V. and Hansom, J.D. (in press) Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D. and Gould, D. (1995) British Regional Geology: The Grampian Highlands of Scotland (4th
edition). British Geological Survey. HMSO, London.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Page 190
10 January, 2002
9
Maps
British Geological Survey Maps: 1:50,000 sheets 38, 45, 46, 53, 54.
Soil Survey of Scotland Maps: 1:250,000 sheet 4 and uncoloured 1:50,000 sheets 49, 50 and 41 cover
most of the Lochaber area. MLURI, Aberdeen.
Page 191
10 January, 2002
ZONE 14
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
ARGYLL WEST AND ISLANDS
Highlights
Rocks of the Rhinns complex and Colonsay Group.
The Lowest-grade metamorphism of the Dalradian Supergroup.
Port Askaig tillite.
World’s oldest discovered animal traces.
Copper and nickel mineralisation and the largest pieces of the mineral pentlandite to be
found in the UK.
The Lorne Lava Plateau.
Western extent of the Clyde Plateau Volcanic Formation.
One of Hutton’s unconformities.
Fossil fish faunas from another sedimentary province distinct from the Midland Valley
and the Orcadian Basin.
Westernmost Scottish Carboniferous.
Rich and diverse Carboniferous fossil fauna and flora.
The best example of a giant myriapod track in Britain.
Permian, Triassic and Cretaceous sedimentary rocks.
The Arran Tertiary volcanic complex.
The most spectacular granite pluton in the British Tertiary Volcanic Province.
The best example of a dyke swarm in the British Tertiary Volcanic Province.
Demonstration of strong geological controls on glacial erosion and coastal topography.
Excellent assemblage of landforms of mountain glaciation in north Arran.
An excellent suite of glacial and glaciofluvial landforms associated with the last ice sheet
and the Loch Lomond Readvance.
An internationally important assemblage of raised shorelines, cliffs, platforms and
estuarine and marine deposits, some pre-dating the last glaciation.
Records of Late-glacial and Holocene palaeoenvironmental change, including human
impacts on the landscape.
Clarity of development of fjordic coastline.
Exemplary development of loch head and fringing saltmarsh, a form restricted to
Scotland and Scandinavia.
Exemplary development of diverse and dynamic beach/dune/machair systems.
Geology
The geology of the zone is diverse and ranges from ancient gneisses, old metamorphosed
and deformed sediments, intrusions and lavas to younger relatively undeformed lavas,
sediments and intrusions. The age range of the rocks is equally impressive: from 1800
million to 60 million years old. The geology reflects a long and complex history, tracing the
movement of ancient continents, the formation of two oceans, the development of a major
mountain belt and several episodes of volcanic activity. The southern part of the zone is
crossed by one of Scotland’s major lineaments – the Highland Boundary Fault.
The oldest rocks, the Rhinns Complex, occur in the SW corner of Islay, and also, to a much
smaller extent, on the northern tip of Colonsay, although the latter are largely concealed by
blown sand. They are of uncertain provenance, but share some similarities with parts of
Greenland and Scandinavia. They comprise a set of ancient Precambrian acid and basic
gneisses, around 1800 million year old. Although of similar age to component parts of the
Page 192
10 January, 2002
Lewisian Complex, the rocks of the Rhinns Complex do not correlate with the Lewisian
gneisses that occur further to the north on Iona.
Sitting upon the Rhinns Complex, and forming the northern half of western Islay, beyond
Loch Gruinart, and the majority of Colonsay, are rocks of the Colonsay Group. The
Colonsay Group, which is of Precambrian age, consists of a sequence of mixed sediments,
principally sandstones, interspersed with phyllites (originally siliceous muds) and limestones.
Both the Rhinns Complex and Colonsay Group rocks are bounded by the Great Glen Fault
to the north and the Loch Gruinart Fault to the SE, the latter coinciding with Loch Indaal
and Loch Gruinart. Correlatives to these two groups of rocks are not found elsewhere in
Scotland, with perhaps the exception of the east coast of Iona in Zone 6, where rocks
similar to the Colonsay Group occur.
The Bowmore sandstone occurs immediately to the east of the Loch Gruinart Fault on Islay.
Owing to the lack of internal fabrics, the correlation of this unit remains uncertain, although
it has tentatively been assigned to the base of the Dalradian.
Rocks of the Dalradian Supergroup dominate the geology of the zone. They are bounded to
the NW by the Great Glen and to the SE by the Highland Boundary Fault, and represent a
thick sequence of sediments originally deposited on a rifting continental shelf. Continued
rifting eventually led to the formation of oceanic crust and the Iapetus Ocean approximately
600 million years ago. Evidence for the emergence of oceanic crust is found at Tayvallich in
the form of pillow lavas. Subsequent closure of Iapetus and continental collision led to the
formation across Scotland of a significant alpine-scale mountain belt, the Caledonides.
During this episode, rocks of the Dalradian were deformed and metamorphosed. The
structures produced, principally large-scale folds, provide a strong NE–SW grain across the
zone and give rise to significant upland features, such as the Paps of Jura.
The Dalradian comprises a wide variety of metamorphosed sediments and volcanics, divided
into four groups (Grampian, Appin, Argyll and Southern Upland Groups) on the basis of
gross lithological characteristics. Zone 14 contains aspects of the last three.
The Appin Group in Zone 14 consists of quartzite, slate, phyllite and limestone. It is
restricted to central Islay and the northern portion of the zone – Lismore (the Lismore
limestone), Shuna and the areas to the north and south of Portnacroish. The sediments are
thought to reflect deposition on a shallow continental shelf. The Argyll Group, occupying
the central portion of the zone, consists of tillite, quartzite, slate and phyllite, and records
the transition from a shelf setting, through a deep-water basin and a return to a tidal shelf,
before the onset of another deep-water basin that persisted for the remainder of the
Dalradian sedimentation. The base of the group is marked by one of the most important
horizons in the Dalradian – the Port Askaig tillite – a lithified glacial till, probably formed by
grounded ice. Recognised throughout the Dalradian, but at its thickest on Islay, the marker
may be correlated with similar horizons around the world and signifies a period of major
glaciation.
The top of the group coincides with marked volcanic activity. A thick pillow lava sequence
and other volcanic deposits are superbly displayed along the west Tayvallich peninsula. A
suite of basic intrusions also occurs within this part of the zone, occupying the limbs of a
major NE–SE-trending fold, the Loch Awe Syncline. In association with the Tayvallich
Page 193
10 January, 2002
volcanics there are copper and nickel mineral deposits, which have been worked in the
mines at Craignure, near Loch Fyne. This area of mineralisation has also yielded the largest
pieces of the mineral pentlandite to be found in the UK.
The Southern Highland Group occupies the south-eastern portion of the zone, and an area
NW of Loch Awe within the Loch Awe Syncline. It comprises a series of grits and lavas. The
grits represent turbidites – submarine avalanches of sediment – deposited in a deep ocean
basin. The volcanics signify continued crustal stretching. The lavas are thickest in the Loch
Awe area.
The structure of the Dalradian is complex. Viewed most simply, the Dalradian of Zone 14 is
distributed into a structure resembling the folded arms of a coat-hanger. The western arm
points upwards to the NW and represents a major fold – the Islay Anticline – whereas the
eastern arm points away to the SE and represents the Ardrishaig Anticline. The tip of the
eastern arm is bent so that it is pointing down at the Highland Boundary Fault. The central
part of the ‘coat-hanger’ resembles a ‘W’ and represent one of the major folds in the
Dalradian, the Loch Awe Syncline. The Dalradian has suffered several phases of deformation.
Significant tectonic breaks within the Zone include the Benderloch Slide, which separates
the Appin Group from the Argyll Group in the Appin area, and the Loch Skerrols Thrust,
separating the Bowmore Group from the Dalradian on Islay. The metamorphic imprint
across the Dalradian is not homogeneous. The highest grades of metamorphism are
reserved for the NE of Scotland. The metamorphic grade throughout Zone 14 is relatively
low. Consequently, many of the original sedimentary features within the rocks are
unobscured.
Detailed mapping in Zone 14 has enabled geologists to develop an accurate picture of basin
evolution in the Dalradian. The changes in the thickness of units and different types of rocks
reveal a complex interplay between sedimentation and basin subsidence along curved faults.
The lack of lateral continuity in places indicates that the Dalradian was deposited in a series
of basins on a subsiding continental shelf, rather than in one extensive basin. Zone 14,
therefore, has proved particularly useful in the study of Dalradian stratigraphy and basin
evolution. In addition, Zone 14 has contributed enormously to understanding the structure
of the Dalradian Supergroup.
In places along the Highland Boundary Fault, there occurs a mixture of rocks characteristic
of ocean floor settings – shales, gabbros, basic volcanic rocks, limestones and phyllites.
Examples occur within Zone 14 in Bute, between Toward and Inellan, and notably at Glen
Sannox on Arran. This marks the line through the zone of the Highland Boundary Fault.
After the formation of the Caledonian mountains, and during the time they were being
actively eroded, volcanism during Lower Devonian times around 400 million years ago
produced the volcanic pile known as the Lorn Plateau lavas. Probably produced from
fissures and occasional vents, the Lorn lavas cover some 300 km2 of Zone 14 and have a
maximum preserved thickness of 800 m. The lavas comprise basalt predominantly, with
minor rhyolite (acid lavas with the equivalent chemistry to granite). Some lavas are rich in
magnesium, nickel and chromium.
In addition to volcanic activity, the Devonian also represents a time when sediment
deposition took place in the zone. Around Oban and on Kerrera a significant sedimentary
Page 194
10 January, 2002
sequence occurs in association with the Lorn Plateau lavas. These deposits, which date from
early in the Devonian (or perhaps uppermost Silurian), represent fluvial and lacustrine
sediments laid down within low-lying areas of the volcanic landscape. Within the larger
bodies of water, arthropods and primitive fish thrived.
Elsewhere in the zone, during the Lower Devonian period, fluvial sediments were laid down
upon the eroded Dalradian rocks. There might have been widespread coverage of these
sediments. However, only remnants now remain on Arran and the southern tip of the Mull
of Kintyre. At Lochranza on Arran, rocks thought to date from the uppermost Devonian, or
lowermost Carboniferous, are seen to overlie deformed Dalradian schists, forming an
unconformity, one of the classic examples referred to by James Hutton.
Not long into the Carboniferous Period, volcanic activity in the Midland Valley area gave rise
to volcanic ashes and lavas, which periodically interrupted normal environmental conditions
and sediment deposition. The coast at Corrie on Arran illustrates good examples of early
Carboniferous volcanic rocks. At Machrihanish the westernmost exposures of the Clyde
Plateau Volcanic Formation occur. These rocks are nationally important as they show
basalts and trachytes of mildly ‘alkaline’ character not seen elsewhere in the Clyde Plateau.
Sea level changes relative to the land in the early Carboniferous, caused in part through
subsidence of the Midland Valley, brought about the periodic inundation of the Midland
Valley by shallow tropical seas. Geologically an extension of the Midland Valley, the southern
half of Arran and the tip of the Mull of Kintyre have Carboniferous sedimentary rock layer
sequences either identical or directly analogous to those in Ayrshire, Lanarkshire and the
rest of the Midland Valley. Lower, Middle and Upper Carboniferous sequences occur in the
zone and comprise fluvial, deltaic and shallow marine deposits, including sandstones,
siltstones, shales, ironstones, coals, seat-earths and limestones. On Arran, the Corrie
Limestone, which has correlatives in Ayrshire, has been extensively quarried and mined. On
the Kintyre peninsula the Machrihanish Coalfield contains several thick, workable coals. In
addition to their past economic importance, the Carboniferous sequences are of value in
palaeogeographic and palaeoenvironmental reconstructions.
Desert conditions persisted over the zone during the Permian geological period and
deposits from this time are quite widespread across the southern half of Arran. These
deposits, which consist primarily of sandstones and conglomerates, also occur at Tayinloan
and Bellochantuy on the Mull of Kintyre, at Port nan Gallan on the Mull of Oa and form the
island of Glas Eilean between Jura and Islay.
On Arran, the Permian sequences merge almost imperceptibly with Triassic deposits, which
underlie a significant area in the south of the island. Of major importance are Jurassic and
Cretaceous sedimentary rock masses within the Tertiary volcanic vent in central Arran.
Although near negligible in extent, these exposures are extremely valuable, bearing
testimony to a once extensive coverage of these rock types over the zone and western
Scotland as a whole.
At the end of the Cretaceous period, the area was lifted above sea level and subjected to
erosion. There then began, from the early Tertiary Period for about12 million years,
volcanic activity associated with the split of northern Europe from Greenland and North
America, with the formation of the northern North Atlantic. This volcanic activity within the
zone therefore represents part of a much larger area of activity that extends along the
Page 195
10 January, 2002
eastern seaboard of Greenland, the western margin of the Rockall Plateau, through the
Faeroes and Iceland.
Elsewhere in western Scotland volcanic ash was the first surface product of the activity
ahead of huge outpourings of lava that piled up to form thick lava plateaux. The lavas were
fed principally from fissures similar to those in present-day Iceland. However, in Zone 14
almost all the lava produced during this initial phase has been lost through erosion, with
only fragments being preserved in the Arran Central Igneous Complex. After the fissure
eruption style of volcanism, activity became centred at regular points along what was to
become western Scotland. Arran became the site of one of six major volcanoes; others
include Mull and St Kilda. Supplied from magma chambers within the crust, the volcanoes
erupted intermittently over a few million years around 60 million to 56 million years ago.
In northern Arran, the mountains represent the eroded remnants of a granite pluton, a
silica-rich rock derived either through differentiation of the basic rocks or through partial
melting of other rocks in the crust. Two distinct granites form the pluton, a coarse-grained
Outer Granite which was intruded first, and a younger fine-grained Inner Granite. The
Outer Granite forms the spectacular mountainous scenery of Northern Arran, whereas the
Inner Granite is less resistant to weathering and is characterised by lower, more rounded
hills. This is regarded as the most spectacular intrusion of its type in the British Tertiary
Volcanic Province. The granite contact with, and its effects upon, the surrounding Dalradian
rocks is well displayed in Glen Catacol. It is noteworthy that the development of the Arran
pluton, had the effect of distorting the NE–SW lineament of the Great Glen Fault
To the south of the granite pluton, the Central Igneous Complex, contains a wide range of
intrusive and extrusive igneous rocks together with remnant masses of Jurassic and
Cretaceous rocks. This mixture of rock types is the result of surface and near-surface rocks
being downfaulted within a major volcanic collapse structure, or caldera, which was
subsequently intruded along its margins by granites.
Along the southern coast of Arran there is a series of 200 or so Tertiary dyke intrusions,
which form striking groyne-like features along the coastal landscape. The dykes consist of
basalt and dolerite, and fill cracks in the crust formed as the crust beneath Zone 14 was
being stretched as a result of the opening of the North Atlantic. Together, these dykes form
a ‘dyke swarm’, the best example in the British Tertiary Volcanic Province and arguably one
of the best examples in the world. Other important Tertiary intrusions in Arran include the
Dippin Sill, Judd’s Dykes and the Drumadoon–Tormore Sill. Their importance is due to their
composite nature, an indicator of the coexistence of acid and basic magmas.
3
Palaeontology
The relatively undeformed Precambrian silty sedimentary rocks of the Bonahaven
Formation, within the Dalradian Supergroup of Islay, have yielded traces of the world’s
oldest known complex organism, a worm-like creature, Neonereites uniserialis, over 600
million years old.
The Uppermost Silurian–Lowermost Devonian ‘fish beds’ on Kerrera and on the mainland
at Gallanach, yield the fossil remains of a fish fauna that lived in a lacustrine–fluvial
environment that was isolated from both main areas of Old Red Sandstone sedimentation in
Page 196
10 January, 2002
the Midland Valley and the Orcadian Basin. The fossil remains of eurypterid water scorpions
are found associated with the cephalaspid fish fauna.
Small outcrops of Carboniferous rocks on eastern Arran and at Machrihanish on the Mull of
Kintyre yield a range of fossil material representing ecosystems that flourished in shallow
marine, brackish lagoon, deltaic, lacustrine and coal swamp environments. At the Cock of
Arran, there is Scotland’s most complete and well-preserved myriapod track produced by a
2-m-long arthropleurid. Further round Arran’s north-east coast at Laggan, the fossil remains
of Carboniferous trees approximately 340 million years old occur in life position. Engulfed
by volcanic ashes, these trees represent a unique fossil forest and are of national
significance.
4
Geomorphology
This area comprises the islands from Colonsay to Arran, together with the Kintyre
peninsula and the coastal fringe from Loch Linnhe to the Clyde. The mainland south of Oban
and west of Loch Long, the northern part of Kintyre, northern Jura and parts of Islay are
predominantly ice-scoured plateau landscapes, with the grain of the topography strongly
controlled by the underlying geological structure. Glacial erosion has also shaped the main
valleys, which are structurally controlled and deeply incised. The lower parts of many of
these valleys have been drowned, including the classic fjord landscape between Loch Fyne
and the Clyde. The northern mountains of Arran display many classic landforms of mountain
glacial erosion. Beyond this zone of glacial erosion, an extensive drift cover on southern
Jura, much of Islay, Kintyre and southern Arran is derived from the last ice sheet. Along the
mainland coastal zone, outlet glaciers from the Loch Lomond Readvance icefield in the
Western Highlands terminated at the mouths of many of the glens, producing moraines,
large outwash fans, outwash terraces and kame terraces. A number of these glacial deposits
are particularly worthy of note:
•
•
•
•
•
•
the Coir’ Odhar and Central Islay moraines on Islay;
the glaciomarine deposits in the Rinns of Islay;
the medial moraine on Jura (Sgriob na Caillich);
landforms associated with ice-sheet recession (Kilmichael valley, Ford–Kilmartin valley,
Glen Euchar)
the ice-sheet recession stage at Otter Ferry;
the Loch Lomond Readvance landforms at South Shian/Loch Creran, Moss of Achnacree,
Gare Loch (Rhu Point).
Also of note is a fossil rock glacier in the Paps of Jura (Beinn Shiantaidh).
The vegetation history of the area is known from several sites, notably Pulpit Hill and Loch
Cill an Aonghais. Pulpit Hill, near Oban, provides an important record of environmental
changes during the Late-glacial. In general, oak forest with birch developed during the middle
Holocene, although birch predominated on the more exposed SW part of Kintyre, on Jura
and on western Islay. Human impact has been inferred from the time of the elm decline, and
possibly earlier on Kintyre.
The coastline of this zone is one of extraordinary complexity and variation and contains the
clearest and best preserved raised beach phenomena in Britain and, perhaps, Europe.
Page 197
10 January, 2002
The influence of the structure and lithology of the underlying bedrock upon coastal form, on
a large scale, is also more clearly expressed here than anywhere else in Britain. Thus the
Firth of Lorne clearly occupies the line of the Great Glen Fault, whereas the striking
similarity in orientation of most sea lochs and islands between Craignish and West Loch
Tarbert on the mainland closely proximates that of the dominant fold axes in this area.
Elsewhere, as for example on Colonsay and Islay, the existence and orientation of most bays
and inlets corresponds to lines of weakness or the strike of softer strata.
On a smaller, more local scale, geological variation profoundly influences the character of
certain coasts and the landforms they exhibit. This is most clearly demonstrated by the dyke
swarms which strike across the shores of southern Arran, resembling a groyne field, and
also those of south-west Jura, which give rise to bold walls, stacks and arches on the
foreshore.
Raised marine deposits and landforms are particularly well represented in this zone and
provide a record of sea level fluctuations dating back to before the last glaciation. Among
the older features are the spectacular glaciated shore platforms on Islay and Jura, the
glaciomarine deposits on Islay and the high-level shelly deposits on Kintyre (Tangy Burn,
etc.), although controversy remains whether the last are in situ. In some areas, such as
around virtually the entire coast of Arran and along the western shores of the Mull of
Kintyre and around Oban and the Firth of Lorne, only one platform is conspicuous (the
Main Rock Platform), albeit superbly exposed and adorned with ancient caves, stacks and
even arches, as on Lismore and at Clach Toll. In other areas, most notably on Jura, Islay and
Colonsay, up to three separate platforms and associated cliff lines are represented (High
Rock Platform, Main Rock Platform and Low Rock Platform). This zone includes the type
areas for these platforms. Raised beaches are manifest widely around the coastlines of this
zone. The oldest and highest features on Jura and Islay relate to the period immediately
after deglaciation and occur at altitudes up to 35 m above the present sea level. Suites of
later shorelines are developed at lower altitudes and blanket the underlying rock platforms.
During the period prior to the Loch Lomond Readvance, thick sequences of fossiliferous
marine deposits accumulated in the estuaries. These are known as the Clyde Beds and in
many places they have been raised by later uplift of the land. Where the Clyde Beds were
incorporated by Loch Lomond Readvance glaciers, they provide an important means of
dating the latter, as at South Shian.
After the Main Postglacial Transgression (c. 7000–6000 14C yr BP) and the formation of an
extensive shoreline (the Main Postglacial Shoreline), four or five lower shorelines were
formed. Important records of these sea level changes are preserved in the sedimentary
deposits in coastal basins (e.g. Moine Mhor and Loch Gruinart).
In sum, the diversity of such landforms and the clarity of their inter-relationships are
unsurpassed in the UK and they are among the finest in Europe.
Contemporary shorelines in the zone are, in comparison, generally unremarkable. Cliff
coastlines do exist, as for example around parts of Jura, the Mull of Kintyre and on Ailsa
Craig, but these are for the most part inherited from glacial or Late-glacial times and
undergo little active marine erosion at present. Shingle beaches are widespread. Along many
shores, and in the more elongate sea lochs particularly, as in the Cowal Peninsula, they are
relatively immobile. In the sheltered headwaters of some of these lochs, sandflats and
saltmarshes have developed. The most extensive marsh is at the head of Loch Gruinart in
Page 198
10 January, 2002
Islay. It is particularly notable for the diverse range of small-scale topographic features, such
as pans, creeks and terraces, that it contains and their relationship with underlying raised
beach deposits.
Large beach–dune complexes are only found on the outer more exposed coastlines of the
zone. A few of these are nonetheless of considerable importance to the study of dune
evolution and for the dynamic behaviour which they exhibit, none more so than Machir Bay
on Islay.
The river systems of Arran show great diversity. The Iorsa Water meanders in a wide,
relatively flat glacial trough, and the presence of standing water suggests that there are
former channels and ox-bows preserved on the floodplain. The presence of Loch Iorsa in
the middle reaches is unusual and can be compared with Loch Insh, a prominent loch in the
middle reaches of the Spey that is a former kettle hole. In contrast, the Glenrosa Water
displays classic downstream channel change, moving from being an upland mountain stream,
through being a wandering gravel bed river, to a meandering river in the middle reaches and
a sinuous river in its lower reaches. The Black Water is constrained in its upper reaches but
debouches onto a flat, wide valley and changes abruptly into a meandering stream, whereas
the Sliddery Water and Allt Duilleachry have bedrock in their lower-middle reaches, which
provides a local base level for braiding and meandering upstream.
The small islands of Seil, Luing, Lismore and Kerrera have no significant river systems. The
watershed of the relatively mountainous Jura runs SW–NE and the freshwater resource of
the island comprises lochs and lochans as well as rivers, which are mainly short, active
mountain torrents or wandering gravel bed rivers with few developed or dendritic
networks. Colonsay and Oronsay have no major rivers, and streams are short and first
order. Like Jura, there is standing water and marsh. The topography of Islay has led to the
east and west having different fluvial characteristics. The east of the island is higher, and
rivers draining east are, in the main, shorter, steeper and more mountainous than those in
the west, where the gentle slopes allow dendritic networks and meandering to develop (e.g.
the tortuous meanders on the River Laggan). Islay also has surface water in the form of
lochs and lochans. Bute is a small island with two different watersheds and some standing
water and marsh. In the north of the island, rivers drain north–south, whereas in the south
the rivers are more sinuous and drain SW–NE east. The island is divided by the extremely
(and perhaps artificially) straight St Colmac Burn, which flows across the flat land from
Kames Bay to Ettrick Bay.
The rivers of Knapdale drain from a SW–NE watershed. The rivers are mostly
topographically constrained, and floodplains only develop to allow meandering in the lowest
reaches. Upland tributaries are steep, although there has been some network development
connecting the standing waters and the streams. In Kintyre, the rivers draining to the east
are relatively short gravel bed streams. The Carradale Water is a major east-draining river
with a wandering gravel bed. Rivers draining west have more developed networks including
lochs and lochans, but channels are mainly wandering gravel bed rivers with sinuous rather
than meandering planforms, and bed material is cobble- and boulder-sized. The Machrihanish
Water is extremely (and artificially) straight in its lower reaches and the floodplain has been
drained to enable agriculture to take place. In Argyll the Oude is straight when constrained
between hills, although its headwater tributaries are more dendritic and incorporate
standing water. On the River Barbeck, weirs in the artificially straightened lower section
provide a base level that has encouraged meandering upstream, whereas the River Add
Page 199
10 January, 2002
meanders along its entire length. The Crinan Canal is an important artificial water feature of
this region.
There are two large freshwater lochs on the mainland, Loch Awe and Loch Eck, which are
in the upper part of their river systems, and also a number of smaller lochs such as Loch
Avich and Loch Scammadale. Loch Eck has short, steep mountain torrents draining straight
into it and more generally the high rainfall coupled with the steep slopes combine to
produce active rivers.
Rivers draining north-west into Loch Awe are mainly short, steep, wooded, cobble-bedded
streams. Of the rivers draining into Loch Fyne, the Array has a number of mountain torrent
tributaries and a wandering gravel bed planform in the upper reaches. The Shira is also a
wandering gravel bed river with a wide floodplain and steep, first-order tributaries, but the
existence of the Dubh Loch in the lower reaches is unusual in a local context. The River
Fyne itself has a number of first-order upland tributaries and alluvial fans, where the steep
tributaries debouch onto the valley floor, which has a more meandering tendency.
5
Soils
The presence of large amounts of fine-grained parent materials and drift in this zone has
given rise to soils that are predominantly surface-water gleys. Impeded drainage is the major
feature of the soils and they support vegetation that is tolerant of high moisture content. In
places where soil permeability is higher and base status improved, soil fertility, and hence
the vegetation it can support, increases and these soils (brown earths) are the most
agriculturally valuable. The calcareous brown earths found on the coastal raised beach sands
are of local significance and represent the higher-quality agricultural soils in this zone. There
are also some soils of national significance such as Rendzinas on Islay and distinctive soils
formed from Triassic marls and sandstones on Arran. Peaty surface horizons are the most
common soil characteristic in this zone and this represents a significant quantity of stored
terrestrial carbon.
6
Summary of key Earth science features in Argyll West and
Islands
The principal Earth heritage interests in Argyll West and Islands are summarised in Table
14.1. Argyll West and Islands includes a total of 61 GCR sites.
Page 200
10 January, 2002
Table 14.1 GCR sites in Argyll West and Islands
GCR block
No. of sites
Principal interests
Dalradian
30
Caledonian Igneous
1
Ordovician Igneous
ORS Igneous
Permo-Carboniferous Igneous
1
1
1
Tertiary Igneous
6
Permo-Trias
2
Westphalian
1
Dinantian
1
Vertebrate Palaeontology
Mineralogy
Palaeobotany
Quaternary of Scotland
1
1
1
11
Coastal Geomorphology
4
Representative sites illustrating features of the
Dalradian Supergroup
Igneous rocks formed as a result of the Caledonian
Orogeny
Igneous rocks formed during the Ordovician Period
Igneous rocks formed during the Devonian period
Igneous rocks formed during the Carboniferous
Period
Igneous rocks formed during the Tertiary Period,
which form part of the British Tertiary Igneous
Province
Representative sites illustrating Uppermost Permian
and Lowermost Triassic sedimentary sequences
Representative sites illustrating Upper
Carboniferous sedimentary sequences
Representative sites illustrating Lower
Carboniferous sedimentary sequences
Devonian age fossil fish
Unusual and rare minerals
Fossil plants from the Carboniferous Period
Glacial and glaciofluvial landforms associated with
the last ice sheet and the Loch Lomond Readvance;
raised shorelines, cliffs, platforms and estuarine and
marine deposits, some pre-dating the last glaciation;
rock glacier; detailed records of Late-glacial and
Holocene palaeoenvironmental change, including
records of woodland history and human impacts on
the landscape
Outstanding examples of beach and machair
landforms, shore platforms and Late-glacial and
Holocene raised shingle ridges; loch head saltmarsh
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in Argyll West and Islands are summarised in Table 14.2. However, there is no
systematic information on current impacts or trends.
Page 201
10 January, 2002
Table 14.2 Potential pressures and vulnerability of Earth heritage interests in Argyll West and
Islands
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction, infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
Vulnerable to irresponsible collecting
Vulnerable to irresponsible collecting
Generally robust
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure
developments; land management changes; construction of
tracks; afforestation; river management
Vulnerable to drainage of bogs and peat extraction
Vulnerable to recreation, development and aggregate
extraction; raised shingle ridges particularly sensitive
Generally robust to all but large scale developments such
as superquarries
Vulnerable to sand extraction, over-grazing, recreation
and coast protection
Vulnerable to sea level rise
Vulnerable to river management, climate change, gravel
extraction and changes in land use management
Vulnerable to land management changes, pollution
Vulnerable to drainage of bogs and peat extraction
Palaeontological interests
Mineralogical interest
Landforms of glacial erosion
Quaternary depositional landforms
and exposures
Palaeoenvironmental records
Raised beaches
Rock coast features
(cliffs and platforms)
Beach/dune systems
Saltmarshes
River geomorphology
Soils
Palaeoenvironmental records
8
•
•
•
•
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Coast defences have obscured a significant part of the interest at Rhu Point.
Scatter of residential housing development along the raised beach at Achnaba-Moss of
Achnacree.
Mineral extraction from beaches is locally a problem, as on Islay.
Fossils are collected from the fossiliferous exposures.
Overgrazing on machair on Islay is locally a problem.
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Region 14.South-west Scotland: Ballantrae to Mull. Joint Nature
Conservation Committee, Peterborough.
Cleal, C.J. and Thomas, B.A. (1995) Palaeozoic Palaeobotany of Great Britain. Geological Conservation
Review Series No. 9. Joint Nature Conservation Committee, Peterborough.
Cleal, C.J. and Thomas, B.A. (1996) British Upper Carboniferous Stratigraphy. Geological Conservation
Review Series No.11. Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Crofts, R. and Ritchie, W. (1973) The Beaches of Mainland Argyll. Countryside Commission for Scotland,
Perth.
Dawson A.G. (1991) Scottish Landform Examples – 3. The Raised Shorelines of Northern Islay and
Western Jura. Scottish Geographic Magazine 107, 207–212.
Page 202
10 January, 2002
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. GCR Series No. 16. Joint Nature
Conservation Committee, Peterborough.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage Commissioned
Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
HR Wallingford, 2000. Coastal Cells in Scotland. Cell 5 – Cape Wrath to Mull of Kintyre. Report to Scottish
Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and Historic
Scotland. SNH RSM Report No. 147. Battleby.
Macklin, M.G., Bonsall, C., Davies, F.M. and Robinson, M.R. (2000) Human-environment interactions
during the Holocene: new data and interpretations from the Oban area, Argyll, Scotland. The
Holocene, 10, 109–121.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Dept. of
Geography, University of Aberdeen. Countryside Commission for Scotland, Battleby, Perth.
May, V. and Hansom, J.D. (in press). Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Ritchie, W.1974. The Beaches of Cowal Bute and Arran. Dept. of Geography, University of Aberdeen.
Countryside Commission for Scotland, Perth.
Ritchie, W. and Crofts, R. (1973) The Beaches of Islay, Jura and Colonsay. Dept. of Geography, University
of Aberdeen. Countryside Commission for Scotland, Perth.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D. and Gould, D. (1995) British Regional Geology: The Grampian Highlands of Scotland (fourth
edition). British Geological Survey. HMSO, London.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Ting, S.1937. Storm waves and shore-forms of south-western Scotland. Geological Magazine, 74,
132–141.
Walker, M.J.C., Gray, J.M. and Lowe, J.J. (1992) The South-West Scottish Highlands. Field Guide. Quaternary
Research Association, Cambridge.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 12, 13, 19, 20, 21, 27, 28, 29, 35, 36, 37, 44, 45.
Soil Survey of Scotland Maps: 1:250 000 sheets 4 and 6 and uncoloured 1:50 000 sheets 55, 63, 62, 61,
60, 68, and 69 cover most of Argyll West and the Islands. MLURI, Aberdeen.
Page 203
10 January, 2002
ZONE 15
1
•
•
•
•
•
•
•
•
•
•
•
•
2
BREADALBANE AND EAST ARGYLL
Highlights
Dalradian Supergroup metamorphic rocks and structures.
Large outcrop areas of the Southern Highland Group of the Dalradian.
Exposures of the Port Askaig Tillite.
Stratabound mineral deposits.
Exposures of the Highland Border Complex.
Occurrence of the only identifiable Cambrian fossils along the Highland Boundary Fault
zone.
Illustrations of Caledonian igneous processes.
Thirteen species of Ordovicain trilobite.
One of the most spectacular contact metamorphic aureoles in the UK.
Glaciated mountains notable for radiating troughs and watershed breaching.
Good examples of Loch Lomond Readvance moraines.
Unusual river landforms, including bedrock features and fluvio-lacustrine features.
Geology
The zone is dominated by a suite of largely Precambrian rocks belonging to the Dalradian
Supergroup. In the south, preserved along the Highland Boundary Fault, there are small, but
important, exposures of younger Cambrian and Ordovician rocks belonging to the Highland
Border Complex. The Highland Boundary Fault is a defining structure in Scotland’s geology,
separating the lower-lying Midland Valley from the mountains to the north.
The Dalradian represents a deformed and metamorphosed sequence of sediments, with
some volcanics, originally deposited in a series of basins on the continental margin of
Laurentia – an ancient continent that comprised North America, Greenland and Scotland,
north of the Highland Boundary Fault. The deformation and metamorphism occurred as the
continents carrying Scotland and England collided, around 400 million years ago, giving rise
to a large mountain chain, stretching from eastern USA through Scotland to Scandinavia.
The mountains we see today are the eroded roots of that chain.
Despite the zone containing aspects of all Dalradian Groups, it comprises predominantly the
two uppermost: the Argyll Group and the Southern Highland Group. These consist mainly
of schists and limestone, with smaller amounts of quartzite, grits and volcanics.
Outcrops within the zone have been important in deciphering the structure of the area.
This part of the Dalradian is dominated by a large, flat, hair-pin fold (the Tay Nappe), the
end of which is bent down at the Highland Boundary Fault. Some of the most important
sites for demonstrating the Tay Nappe are Little Glen Shee and the Sma Glen.
Elsewhere, important sedimentary features occur. A glacial tillite (the Port Askaig tillite)
outcrops at Tempar Burn, NW Schiehallion, and correlates with similar units elsewhere
within the Dalradian. These are important outcrops in understanding the processes of
worldwide glaciation that took place at this time.
Important mineral-rich layers, commonly referred to as ‘stratabound’ deposits, occur within
the zone. The mineralisation comprises baryte, baryte silicates, metal sulphides and
Page 204
10 January, 2002
chromium minerals, with the largest concentration occurring near Aberfeldy at Ben Eagach
Quarry and the Foss mine. Similar deposits, although far less extensive, occur at Beinn
Heasgarnich. The deposits are thought to have formed as exhalative metalliferous brines on
the seabed at the same time as the host sediments.
Along the southern edge of the zone – intermittently between Keltie Water and Balmaha –
outcrops of the Highland Border Complex occur. They are thought to represent remnants
of oceanic crust and comprise ultrabasics, limestones, shales and basic lavas. The
relationship between these and the Dalradian to the north remains unclear. To this end, the
outcrops within the Keltie Water, at Callander, have been the subject of much recent study,
since they straddle the Highland Boundary Fault and contain both Dalradian and Highland
Border Complex sediments. The Leny Limestones at the Leny Quarry near Callander is on
the boundary between Zones 15 and 17. This is the only locality along the Highland
Boundary Fault Zone that yields identifiable Cambrian fossils. The site is of national
significance because the presence of the Lower Cambrian fossils is a crucial factor in the
arguments on the age of the Dalradian Supergroup and of the event that deformed and
metamorphosed the Supergroup. It is still debated whether the Leny Limestone is part of
the Dalradian Supergroup or is part of the Highland Border Complex Sub-terrane. In
contrast, the Dounans limestone at Lime Craig Quarry on the Highland Boundary Fault
zone near Aberfoyle has yielded Ordovician fossils. The character of the sedimentary
sequence and the fossil content suggest that the Highland Border Complex shared none of
its pre-Devonian history with the Dalradian rocks to the north.
Relatively few intrusions occur. The two largest are Garabal Hill in the west and Comrie in
the east, close to the Highland Boundary Fault. Both are dated around 407 million years old
and are associated with continental collision at that time. The Comrie pluton, which was
derived through partial melting of lower crustal rocks during the deformation and
metamorphism of the Dalradian Supergroup, is unusual in that it is isolated from the other
Caledonian intrusions such as the Cairngorm granite. It is however, a fine example of a
zoned pluton with a core of granitic rocks surrounded by less silica-rich dioritic rocks. The
edge of the Comrie pluton is one of the most spectacular examples of a contact aureole in
the UK. A contact aureole is the zone around a cooling pluton that illustrates mineralogical
changes as a consequence of being baked by the cooling magma.
Comrie is also notable as a site of seismic activity and the first purpose-built seismological
observatory.
3
Palaeontology
Sedimentary rocks of Cambrian and Ordovician age within the Highland Border Complex, at
Callander and elsewhere along the southern margin of the zone, yield rare but nationally
important marine shelly faunas that have been used to develop models explaining ancient
palaeogeographies and the evolution of Scotland’s foundations. The Cambrian and
Ordovician fossil faunas associated with the sequences along the Highland Boundary Fault
zone have a distinct North American affinity, which supports the existence of the Iapetus
Ocean. The Dounans Limestone at Lime Craig Quarry has yielded, brachiopods, gastropods,
bryzoans, ostracods, crinoids, an orthocone and 13 species of trilobite.
Page 205
10 January, 2002
4
Geomorphology
The zone includes the Western Grampian mountains south of Rannoch Moor and extending
from west of Loch Lomond to east of Ben Lawers. This area has been heavily modified by
glacial erosion, although to a slightly lesser extent than that to the north. Broadly the area
shows a radial pattern of glacial troughs in the south-west, emanating from the former ice
centre in the Rannoch area. In part, the powerful ice streams followed the lines of preexisting valleys, and in part breached new routes through the pre-existing watersheds (e.g.
Loch Lomond). To the east, the general alignment is E–W or SW–NE, reflecting underlying
geological controls. The mountains in the west are heavily ice scoured, but the intensity of
glacial erosion decreases eastwards. Drift cover in the valleys is generally extensive and
includes good examples of moraines, particularly within the limits of the Loch Lomond
Readvance, as around Tyndrum, Glen Dochart, Glen Artney and Glen Turrett.
Two distinct zones of woodland development are recognised during the middle Holocene.
In the west, oak and birch developed, whereas pine was predominant in the east.
Zone 15 contains no coastline, save for a few kilometres of relatively sheltered shoreline
around the head and eastern side of Loch Long. The loch represents a drowned glacial
valley and its shores are dominated by generally inactive shingle reworked from adjacent till
deposits, along with occasional thin patches of sand and sporadic rock outcrops.
Breadalbane and East Argyll has diverse fluvial interests, containing rivers draining in all
directions and large lochs, mainly located within the upper reaches of the river systems.
Major lochs include Lochs Lomond, Tay, Katrine and Rannoch, and the high rainfall and the
steep slopes combine to produce active rivers with high sediment loads. A number of lochs
are fed by short, steep mountain torrents draining straight into them, including Loch Tay,
Loch Lubnaig and Loch Lomond.
The River Fillan (an easterly flowing tributary of the Tay) appears to drain an alluvial basin,
and meanders and divides in a locally widened basin. Its tributaries are mainly steep
mountain torrents but after becoming the Dochart it meanders in its middle reaches. There
are a number of small lochs within the system (before it reaches Loch Tay). The Falls of
Dochart is a notable as a wide and shallow bedrock reach. The upper and middle reaches of
the east-flowing Lyon, Almond and Earn are braided or have braided meanders, whereas the
Braan is more meandering within this zone. The braiding downstream of the Lyon’s
confluence with the Tay indicates that both rivers still carry a high sediment load (despite
the Tay passing through the potential sediment sink of Loch Tay). The planform of the River
Balvag is mainly meandering, but its delta has prograded in a straight or slightly sinuous
fashion into Loch Lubnaig and this unusual lacustrine environment is also a fluvial
geomorphology GCR site.
5
Soils
The predominant soils in this region are podzols and surface-water gleys, which reflects the
texture of the parent materials on which soil formation has occurred. Brown earth soils are
found in places where the base status of parent materials is high (i.e. on limestone or basic
parent rock), and where topography allows, these soils are the most agriculturally
productive. Peat is found in upland regions where impeded drainage and high acidity result
in organic matter accumulation. The east–west trend of the valleys results in soil
Page 206
10 January, 2002
development differences according to aspect. Podzols account for 43% of the soils in this
zone, surface-water gleys 20%, and peats 13%. This means that the soils in this zone contain
substantial carbon reserves. Soils of national significance include alpine podzols on Ben
Lawers, brown earths on islands in Loch Lomond and iron podzols in Rannoch Black Wood.
6
Summary of key Earth science features in Breadalbane and
East Argyll
The principal Earth heritage interests in Breadalbane and East Argyll are summarised in
Table 15.1. Breadalbane and East Argyll includes a total of 19 GCR sites.
Table 15.1 GCR sites in Breadalbane and East Argyll
GCR block
No. of sites
Principal interests
Dalradian
Cambrian
8
1
Arenig-Llanvirn
1
Caledonian Igneous
4
Representative sections of the Dalradian Supergroup
Representative sections of Cambrian sedimentary sequences
along the Highland Boundary
Representative sections of Ordovician sedimentary
sequences along the Highland Boundary
Igneous rocks formed as a result of the Caledonian
Orogeny, important in understanding magmatic processes.
Important mineralisation
Unusual river landforms, including bedrock features and
fluvio-lacustrine features
Mineralogy
2
Fluvial Geomorphology
7
2
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in Breadalbane and East Argyll are summarised in Table 15.2. However, there is
no systematic information on current impacts or trends.
Page 207
10 January, 2002
Table 15.2 Potential pressures and vulnerability of Earth heritage interests in Breadalbane and East
Argyll
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Generally robust
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments; land
management changes; construction of tracks; afforestation;
river management
Vulnerable to drainage of bogs and peat extraction
Vulnerable to mineral extraction from beaches; coast
protection; commercial and industrial developments land claim
and sea level rise
Vulnerable to river engineering and management; afforestation;
gravel extraction; land management changes
Vulnerable to land management changes, pollution, peat
erosion
Palaeontological interests
Landforms of glacial erosion
Quaternary depositional landforms
and exposures
Palaeoenvironmental records
Coastal features
Fluvial geomorphology
Soils
8
State of the resource
Information on individual GCR sites is available from the Earth Science Site Documentation
Reports.
9
Bibliography
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage Commissioned
Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Mather, A.S. and Smith, J.S. (1974) Beaches of Shetland. Perth, Countryside Commission for Scotland.
May, V. and Hansom, J.D. (in press). Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland, Methuen, London.
Stephenson, D. and Gould, D. (1995) British Regional Geology: The Grampian Highlands of Scotland (fourth
edition). British Geological Survey. HMSO, London.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 38, 39, 46, 47, 54, 55, 56.
Soil Survey of Scotland Maps: 1:250,000 sheets 4, 5, 6 and 7, coloured 1:63,360 sheet 47 and uncoloured
1:50,000 sheets 51 and 57 cover most of Breadalbane and East Argyll. MLURI, Aberdeen.
Page 208
10 January, 2002
ZONE 16
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
EASTERN LOWLANDS
Highlights
Contains elements of three major geologically distinct terranes.
Illustrates to good effect the Highland Boundary Fault zone.
Encompasses the most extensive area known of the Highland Border Complex.
Contains a portion of the Dalradian Supergroup.
Encompasses the eastern end of the Southern Uplands accretionary prism.
Devonian fossil fish and arthropods of international significance.
Devonian fossil plant remains.
Arthur’s Seat, which is the one of the best examples in the world of a dissected volcano.
Encompasses the Midlothian Coalfield.
Carboniferous fossil fish and amphibian remains.
Carboniferous fossil plants of international significance.
The first recorded occurrence of the conodont animal.
The occurrence of ‘Elie Rubies’.
Excellent examples of ice-moulded lowlands, including the Tweed valley drumlins, and
lowland hills.
Excellent examples of a wide range of glacial and glaciofluvial deposits and meltwater
channels, which provide important evidence for the pattern of ice movement and
deglaciation of the last ice sheet.
Records of Late-glacial and Holocene palaeoenvironmental change, including forest
history and human impacts on the landscape
Detailed records of Lateglacial and Holocene relative sea level changes.
Clarity and diversity of cliffs and rock coast landforms in volcanic rocks.
Exceptional dynamism of beach and dune systems related to both human and natural
factors.
Extent, magnitude and impact of coastal erosion.
Most rapidly prograding (advancing) shoreline in Scotland.
Excellent examples of coastal forelands.
Most clearly developed parabolic dunes in Scotland.
Most extensive mudflats and saltmarshes, outside the Solway.
Exemplary development of carse (raised saltmarsh) deposits.
Classic ‘trumpet-shaped’ estuarine morphology.
Clarity of evidence of human influence on coastal processes and evolution.
Geology
The rocks underlying Zone 16 are largely sedimentary in origin and in the main were laid
down during three geological periods: the Silurian, Devonian and Carboniferous. Silurian
rocks form part of the Southern Uplands, and underlie much of the SE portion of the zone,
south of the Southern Upland Fault. Devonian rocks dominate the northern part of the
zone, with Carboniferous sequences underlying the central areas. The zone straddles two
major geological faults in the crust of Scotland; the Highland Boundary Fault and the
Southern Upland Fault.
The oldest rocks in the zone form part of the Dalradian Supergroup. These occur at its
north-eastern margin, in association with the Highland Boundary Fault, at Garron Point just
north of Stonehaven. The Dalradian Supergroup is confined to the area defined by the Great
Page 209
10 January, 2002
Glen Fault to the NW and by the Highland Boundary Fault to the SE. The supergroup
represents sediments and volcanics originally laid down on, or in the case of the volcanics
erupted onto, the southern margin of a continent, referred to by geologists as Laurasia,
during the Precambrian and Cambrian periods between 700 million and 600 million (and
very possibly as recent as 500 million) years ago. The Laurasian continent comprised North
America, Greenland and the north-westernmost part of present-day Scotland and was
separated from what is now England and northern Europe by the Iapetus Ocean.
In late Cambrian and through Ordovician times, the Dalradian Supergroup underwent
deformation and metamorphism as the Iapetus Ocean closed, with the continental collision
between Laurasia and a northern European continental landmass. This gave rise to the
eventual coming together of the crustal foundations that constitute Britain. On a large scale,
the collision, termed the Caledonian Orogeny, gave rise to an alpine-scale mountain belt,
termed the Caledonides.
The Highland Boundary Fault, which came into being during the Caledonian Orogeny,
represents a fracture in the crust that separates two major crustal components of Scotland,
these being the Grampian Highlands, comprising rocks of the Dalradian Supergroup, and the
Midland Valley. Between these two masses of crust along the line of the fault there lies the
Highland Border Complex, the best exposure of which occurs at the north-east of the zone
at Craigeven Bay. This complex comprises Cambrian to Ordovician age pillow lavas and
Ordovician to Silurian age sediments, which represent a slice of an ocean floor that once
existed between the Dalradian Supergroup and the area that was to become the Midland
Valley. Although of small outcrop area, these rocks are of enormous importance in
unravelling the geological history of the zone and the country as a whole.
It was within the Iapetus Ocean off the coast of Laurasia that the Ordovician and Silurian
rocks within the southern half of the zone were deposited. These rocks consist of shales,
mudstones and greywackes (coarse grained muddy sandstones) that have been folded and
extensively faulted and very mildly metamorphosed with the closure of the Iapetus Ocean,
during the Caledonian Orogeny. These rocks occur between Hawick and Galashiels and
around Grantshouse and form the easternmost hills of the Southern Uplands. They form a
structure known as an accretionary wedge, modern examples of which occur in the Far East.
By late Silurian and early Devonian times the crustal fragments that underlie the zone, and
Scotland as a whole, were coming together and the Iapetus Ocean had closed. Hot arid
environmental conditions persisted across the zone at this time, and river-deposited
conglomerates and sandstones accumulated in the Midland Valley area. Lower Devonian
sediments underlie all the northern margin of the zone from Stonehaven in the north east,
through Strathmore to Thornhill in the south-west. At Slug Head, near Stonehaven the
unconformity between the Silurian–Devonian sequence and the Highland Border Complex
is well exposed. Lower Devonian rocks also occur south of Dunbar.
Despite the closure of the Iapetus Ocean and the cessation of the crustal upheavals
associated with the Caledonian Orogeny, crustal instability continued during Devonian
times, resulting in volcanic activity that produced lavas and ashes. The Crawton Volcanic
Formation is a result of such activity. Well exposed at Crawton Bay, south of Stonehaven,
this formation forms an important marker horizon that can be traced over a large area
within the Devonian sedimentary sequences along the northern edge of the zone. The main
areas of the zone underlain by Devonian volcanics correspond to the Ochil and Sidlaw Hills
Page 210
10 January, 2002
and a large area to the east of Jedburgh at the margin of the Cheviots. Other outcrops of
Devonian volcanics occur at St Abb’s Head, around Coldingham and west of Eyemouth.
The Carse of Gowrie, Montrose and Loch Leven are underlain by sandstones and other
finer-grained sediments laid down during Upper Devonian times. There was a cessation of
sediment deposition during Middle Devonian times in the Midland Valley and hence only
Lower and Upper Devonian rocks are present. Upper Devonian sequences also underlie the
area to the east of Lauder and around Jedburgh. On the coast at Siccar Point there is the
world famous ‘Hutton’s Unconformity’, where uppermost Devonian rocks rest upon
deformed rocks of Silurian age. Using the geological evidence at this locality James Hutton,
among others, formulated his theory of the Earth that formed the basis of modern geology.
Siccar Point is therefore of major historical importance.
Whereas the Devonian environment consisted of desert and river deposits, laid down in a
basin between the Caledonian mountains to the north and the newly emergent Southern
Uplands to the south, the Carboniferous Period saw an increasing marine influence. Cyclic
sedimentation developed, with the formation of deltas, swamps, lagoons and shallow marine
conditions. Consequently, the Carboniferous sequence comprises a greater variety of rock
types: limestone, coal, sandstones, siltstones, oilshales and mudstones. During this period,
Scotland drifted across the equator.
Two main areas of deposition existed within the zone during the Carboniferous, one on
either side of the Southern Uplands. In the north there was the Midland Valley, which
encompasses rock sequences that span most of the Carboniferous, and in the south, the
Solway–Northumberland basin, which yields rocks of Lower Carboniferous age.
Within the Midland Valley, Lower Carboniferous rocks underlie much of the east Fife area,
between Edinburgh and Bo’ness and between Aberlady and Cockburnspath. These Lower
Carboniferous sequences contain thick limestones such as the Charlestown Main Limestone
and the East Lothian Oil-shale deposits, both extensively quarried and mined in the
nineteenth and twentieth centuries. Upper Carboniferous rock layer sequences occur at the
centre of the zone at its western margin and in the area between Penicuik and Leven in Fife;
these correspond to the Central and Midlothian Coalfields respectively. In addition to thick
workable coals, these coal-bearing sequences consist of sandstones, siltstones and seatearths.
Throughout Zone 16, the sediments of the Carboniferous are interspersed with volcanics
and igneous intrusions brought about by continuing crustal instability. Lower Carboniferous
lavas are found in East Lothian (e.g. Garleton Hills), West Lothian (e.g. the Bathgate Hills)
and around Burntisland in Fife. Arthur’s Seat in central Edinburgh represents the remains of
a dissected volcano, one of the best examples of its kind in the world. The remains of
volcanic vents also occur along the coast at North Berwick; these structures are of
particular significance through the occurrence of xenoliths within the vent rocks that have
travelled from the lower crust, thus providing an insight into the geology of the Midland
Valley at depth. At Elie Ness on the Fife coast an unusual magma has given rise to the
occurrence of pyrope garnets, which weather out to form the famous ‘Elie Rubies’.
Carboniferous igneous intrusions form prominent features such as the Salisbury Crags,
North Berwick Law and Traprain Law. Numerous exposures occur throughout the central
Page 211
10 January, 2002
part of the zone of the Midland Valley Sill, an extensive and thick, homogeneous dolerite,
which is well exposed at the northern end of the Forth Road Bridge.
Volcanism continued into the Permian period and numerous vents and plugs throughout
East Fife are testimony to this activity.
3
Palaeontology
The extensive Lower Devonian lacustrine–fluvial sequences of the northern areas of the
zone, which were laid down between 400 million and 380 million years ago, have yielded
fossil fish and arthropod faunas. Wolf’s Hole Quarry at Bridge of Allan, Whitehouse Den
near Dundee and Turin hill in Angus have all yielded early Devonian fossil fish. Wolf’s Hole
is a type locality for several fossil fish and is therefore of international significance. The
arthropod fossils at Turin Hill are nationally significant and represent the remains of water
scorpions, which dominated the aquatic environment before the evolutionary explosion of
the fish. Smaller, although highly significant, exposures of Upper Devonian fluvial sequences,
at the south-east corner of the zone, on the coast in the vicinity of Cove, near Pease Bay,
have yielded the remains of primitive armoured fish. Throughout the Lower Devonian
sequences, the fossil remains of a primitive plant flora found at sites such as Ballanucater
near Callander and at Turin Hill represent some of the earliest terrestrial plant life on the
planet.
In Fife and across to the Lothians and around the Southern Uplands to the Borders,
Carboniferous sequences yield a plethora of fossil faunas and floras, indicative of a
multiplicity of constantly changing environments that existed between 360 million and 290
million years ago. Elements of this ancient fauna and flora are of international significance,
such as the perfectly preserved Lower Carboniferous diverse plant flora found at Pettycurr
in Fife and the fish and amphibian remains found at Wardie and Inchkeith in the Lothians.
The fossil-rich sites at Foulden Burn and the Whiteadder River are also of international
importance as type localities for Carboniferous fossil fish and plants, respectively. One of
the most important fossil discoveries within the zone took place in 1982, when the first
ever remains of the conodont animal were discovered in the Granton ‘shrimp bed’.
4
Geomorphology
This diverse area encompasses (1) the lowland straths, valleys and adjacent hills of the
eastern Central Lowlands and (2) the Tweed valley. The broad outlines of the landscape of
the former area reflect the underlying geological controls on differential erosion on the
varied sedimentary and volcanic rocks. The whole area has been modified by the effects of
glacial erosion and deposition during the Quaternary ice ages. The straths and valleys have
been deepened and the hills moulded and streamlined by the passage of the ice. Particularly
striking examples of such moulding are represented in the crag and tail forms and
streamlined bedrock of Midlothian and East Lothian, and the hills along the margins of the
Tweed valley. The lower ground is extensively mantled by a cover of drift deposits from the
last ice sheet, comprising variable thicknesses of till and sand and gravel. In many cases these
deposits have a range of surface forms, including drumlins, eskers, kames and outwash
terraces. Notable areas include the Highland edge along Strathmore (glaciofluvial deposits),
NE Fife (glaciofluvial deposits), Strathallan and the Teith valley (glaciofluvial deposits) and the
Tweed valley (drumlins). Locally, extended sequences of deposits occur that are critical for
Page 212
10 January, 2002
interpreting the glacial history of Scotland, as at Burn of Benholm. Here, Early Devensian
interstadial organic deposits form part of an important sequence that also includes rafts of
sediment derived from the floor of the North Sea. The Almondbank area north of Perth
also provides critical evidence for testing the validity of the Perth Readvance. Meltwater
channels are common along many of the lower hillslopes, particularly bordering the
Highland edge, the Pentland Hills, the Ochil Hills and the northern flanks of the
Lammermuir Hills. The western Forth Valley and the Teith Valley around Callander provide
crucial evidence for the Loch Lomond Readvance. During and immediately after deglaciation,
thick sequences of fossiliferous marine deposits accumulated in the estuaries – the Errol
Beds, so named after their type area at Errol. Radiocarbon dates on shells from the Errol
Beds provide important dates for deglaciation of the east coast of Scotland. In the Forth and
Tay estuaries, outwash sediments often grade into the raised beaches, with younger features
being found farther west, reflecting periods of progressive ice-sheet retreat. The Main Perth
Shoreline may be related to a major halt stage in the retreat of the ice.
The coastal lowlands and the Forth and Tay valleys provide widespread evidence of
Holocene sea level changes in the form of suites of raised shorelines and the extensive
development of carselands. Among the key localities are Milton Ness, the Montrose basin
area, the Errol area, lower Strath Earn, the east and south coasts of Fife, the western Forth
Valley, the south coast of the Forth and the Dunbar area. The western Forth Valley has one
of the most important records of relative sea level change in Scotland. Here a sequence of
buried beaches and carse deposits provide an unparalleled record of changes during the last
c.11 ka. This area is important, both in a historical context and for the detail of its records,
and may be regarded as the core area for modern sea level studies in Scotland. The Main
South-west Shoreline and its backing cliff line are a prominent feature of the coastal
landscape of the zone. During the middle Holocene, the east coast of Scotland was affected
by a tsunami generated by a submarine slide on the Norwegian continental slope; the
evidence for this is best seen at Maryton, near Montrose.
The coastal zone was largely dominated by glacial deposition which has provided an ample
sediment supply for the development of extensive areas of raised beach, sand dune and
shingle beach, as at Tentsmuir and Aberlady. Intervening areas of coastline show welldeveloped cliffs and shore platforms developed in a variety of rock types. Inland from the
coast, glaciofluvial sands and gravels occur extensively in the main valleys; elsewhere, till
sheets predominate. The major valleys such as the North Esk and South Esk also acted as
sediment sources to the coast during and following deglaciation. The Tweed valley has the
form of a broad, ice-moulded basin with a drift cover that is extensively drumlinised, which
gives a strong topographic grain to the landscape. River terraces are prominent along the
valley axis, reflecting the changes in sediment input and river discharges during and following
the last deglaciation.
The patterns of vegetation history and environmental change spanning the last c.14 ka have
been determined from numerous sites in the area (e.g. Stormont Loch, Black Loch, Whitrig
Bog, Beanrig Moss and Din Moss). Whitrig Bog has provided critical information for the
period of the Last Glacial–Holocene transition, including tephra marker horizons, and data
from the site have been used to establish correlations with the Greenland ice-core proxy
climate records for this key time period.
During the middle Holocene, a mixed deciduous forest of mainly oak, elm with alder and
birch developed.
Page 213
10 January, 2002
The coastline of NHZ 16 is, like that of Zone 9 to the north, one of contrasts. Cliffs,
beach–dune complexes, mudflats and saltmarsh are all superbly represented. The most
distinctive characteristic of this coast is, however, its dynamism and propensity for change,
related to both natural and anthropogenic factors.
From Stonehaven south to Carnoustie, St Andrews around to Elie and Dunbar east to the
Border, the coastline is predominantly rocky and cliffed, albeit with numerous pocket
beaches and fine beach–dune systems at certain locations, such as Montrose Bay and Lunan
Bay. Although some of these cliff lines are inherited from glacial or even pre-glacial times,
others are actively eroding to this day. Particularly notable in this respect are those around
Dunbar and at St Abb’s Head, where differential erosion linked to fractures and lithological
variations in suites of volcanic rocks has created a wealth of clearly formed but intricate cliff
features. Other volcanic rocks intruded through the sedimentary strata that dominate this
zone tend to resist coastal erosion more than the surrounding sediments and are left
upstanding as distinctive stacks or cliffed islands such as the Rock and Spindle near St
Andrews and the Bass Rock. At Earlsferry and Dunbar, evidence of formerly higher sea
levels is engraved in the coastal landscape as a series of raised terraces and platforms
respectively.
Around the mouths of the Tay and Eden, massive beach–dune complexes dominate the
coastline. Those of Barry Links and Tentsmuir have developed on top of vast prograding
forelands which have grown out 3–4 km from the postglacial shoreline (i.e. in the last
5000–6000 years). At Barry Links, exceptionally well-developed parabolic dunes have drifted
across the foreland, unlike any in the rest of the UK. Parts of the Tentsmuir coast still
represent the most actively prograding areas of the Scottish coastline, having advanced 100
m in the last 50 years. By contrast, an average of 4 m of coastal retreat has occurred
annually within certain dune systems around Montrose, representing one of the most rapidly
eroding areas of coastline in Scotland.
Relatively sheltered conditions prevail in Montrose Basin and the Tay, Forth and Eden
estuaries and appreciable quantities of sediment continue to be supplied to these areas from
marine and fluvial sources. Consequently, wide expanses of mudflat, sandflat and saltmarsh
exist in these areas. Indeed, those of the Tay and Forth are more extensive than any in
Scotland outside the Solway Firth.
Finally, although natural factors are the dominant criteria forcing change in this coastline,
human factors have influenced coastal dynamics in this zone more than in any other. Most
significant of these is the 1–2 m, and exceptionally 5 m, of coastal subsidence that coalmining activities have caused in the East Wemyss area of Fife and the loss of 50% of the
intertidal area of the Forth, upstream of the Bridges, which coastal development and land
claim has caused in the last two centuries.
In general, this zone comprises an area of low-lying coastal fringe. In consequence, the rivers
situated within the zone are mainly the lower meandering reaches of larger systems, and the
zone is divided into three geographic areas by two major east-coast estuaries and their
tributary river systems. The River Forth meanders irregularly along most of its length, with
the meanders becoming particularly tortuous downstream of Stirling, where the river is
tidal. The main tributaries of the Forth in this zone are the River Teith, which is relatively
straight after debouching from a bedrock section at the zone boundary near Callander, and
the Allan Water, which is sinuous in its upper reaches before meandering downstream. The
Page 214
10 January, 2002
Allan Water has been extensively engineered near Bridge of Allan. The Devon catchment is
extremely unusual. Its west-flowing route is the result of headwater capture, and whereas
the Devon has a meandering planform and cut-offs on the floodplain, its headwaters are in
the uplands. Zone 16 also includes the downstream reaches of the Pow Burn and the River
Carron, which flow east into the Forth Estuary, and the Rivers Avon, Almond, North Esk,
South Esk and Water of Leith, which flow north and north-east into the Forth Estuary. All
these rivers meander irregularly in this zone, and some meander tortuously. The extent of
meandering is a function of the low-energy environment created by the flat coastal land and
the undulating rather than mountainous headwaters. The development of channel planform
on the meandering reaches of rivers draining through and towards Edinburgh (e.g. the
North and South Esk, Water of Leith and Almond) is increasingly constrained by
development pressures and flood embankments.
The Tweed and its tributaries (which include the Ale Water, Leader Water, Blackadder,
Whiteadder, Ettrick Water, Gala Water, River Teviot, and Ey Water) all meander at some
point in the zone, with the meanders become increasingly tortuous downstream. This is also
true of the River Tyne, Dry Burn and Peffer Burn which flow east into the North Sea. The
low energy of the system means that channel planform change is often gradual in this zone,
and usually results from the erosion of the outer bank of meander bends (which can lead to
channel cut-off). The exception is the ‘badland’ topography of parts of the Southern
Uplands, typified by the Oldhamstocks Burn GCR site, where rapid incision into till or weak
bedrock occurs during high storms. The Leader, Gala and Whiteadder Waters drain the
southern side of the Lammermuir hills, and thus the upper parts within the zone are mainly
steep active boulder bed tributaries. Their middle, wandering gravel bed reaches show
elements of sinuous and divided behaviour, which becomes meandering and increasingly
tortuous in the lower reaches. Some meanders are rectangular in form, and parts of the
Whiteadder are constrained, ensuring that meandering only occurs where the floodplain
opens out.
The main river draining Fife is the Eden, which ends in the silty Eden Estuary. Its headwater
streams also start within this lowland zone, and, in consequence, the tributary system is
dendritic. In the middle and lower reaches the Eden meanders, and channel sinuosity
depends upon the degree of channel confinement (with the Eden being constrained around
Dairsie and Tarvit). The course of the River Leven, which drains the large surface-water
body of Loch Leven, was straightened during the Industrial Revolution to supply water to
mills. Downstream of Markinch, it becomes increasingly natural and meanders more,
becoming sinuous after the confluence with the River Ore, whose wandering and divided
headwaters drain areas of water-filled mining pits. Fife also has a number of reservoirs for
water supply and burns that have been straightened to aid farm drainage. The lower reaches
of the Earn, which flow into the Tay Estuary north of Fife, are meandering, and there are a
number of cut-offs and ox-bow lakes on the wide floodplain floor showing that it is (or has
been) active. Its tributary streams drain steeper slopes and comprise higher-energy
wandering gravel bed rivers that form alluvial fans at the confluence with the Earn. These
tributaries can be extremely active during flood.
The lower Tay meanders in its downstream reaches near Perth, although there are still a
number of lateral gravel bars in the main channel. The River Tay has the highest average
discharge of any river in Britain, so it is a major and significant river system. The River
Almond drains east from a source close to Loch Tay and is a major west-bank tributary of
the Tay in this zone. The Isla is a major east-bank tributary of the Tay, with a confluence
Page 215
10 January, 2002
north of Perth. The Isla meanders in its lower courses and also has a number of meandering
tributaries. Below Perth the Tay is a tidal river. Many of the water courses in the Carse of
Gowrie flow into the Tay Estuary. The Carse was drained for agricultural purposes and
much of its drainage system comprises straight farm drains with only a few naturally
meandering streams. The Lunan Water and the Dighty Water drain south-east and are
mainly sinuous. This contrasts with the Monikie Burn, where the meanders become
tortuous in the lower reaches. The planforms of the North and South Esk and the Bervie
Water are mainly meandering in the middle and lower reaches. A number of the meanders
in the South Esk are rectangular but both rivers becomes sinuous before entering the North
Sea, the South Esk doing so via the silty Montrose Basin. The upper North Esk and its
tributary the West Water are notable for terraces and palaeochannels formed during the
deglaciation of the last ice sheet.
5
Soils
The textural properties of the parent drift materials in combination with climate of this zone
have produced a large number of brown earth soils that have high potential for arable
agriculture. By virtue of climate, the soils are less heavily leached and more biologically
active, and hence soil development is moderated. Where soils are formed of fine-textured
drift material, surface-water gleys develop which require drainage to improve agricultural
potential. The soils in this zone are the most fertile in the country but also have the biggest
demand from urban/industrial sources. Soils of national significance include buried aeolian
soils in Tentsmiur Forest, Fife, and ‘plaggen’ soils near Carnoustie. Soils of local significance
include isolated basin peat deposits at Flanders Moss and Loch Glour. A long history of
intensive agriculture in this zone has led to problems such as soil erosion and decline in
fertility in some areas. Soils have been affected by contamination from urban/industrial
sources and have been lost by hard development.
6
Summary of key Earth science features in Eastern
Lowlands
The principal Earth heritage interests in the Eastern Lowlands are summarised in Table 16.1.
The eastern Lowlands includes a total of 96 GCR sites.
Page 216
10 January, 2002
Table 16.1 GCR sites in Eastern Lowlands
GCR block
No. of sites
Principal interests
Dalradian
1
Caledonian Igneous
2
Ordovician Igneous
Permo-Carboniferous Igneous
1
12
P–C Fish/Amphibia
Old Red Sandstone Igneous
Non-marine Devonian
Dinantian
4
7
5
12
Llandovery
Westphalian
1
2
Palaeozoic Palaeobotany
Arthropoda
Vertebrate Palaeontology
Mineralogy
Quaternary of Scotland
8
3
5
4
24
Coastal Geomorphology
4
Fluvial Geomorphology
2
The Highland Boundary Fault and its contact with
the Dalradian Supergroup
Igneous rocks formed as a result of the Caledonian
Orogeny
Ordovician igneous rocks
Igneous rocks formed during Carboniferous and
Permian times
Fossil fish from Carboniferous/Permian times
Igneous rocks dating from the Devonian period
Devonian terrestrial sediments
Representative Lower Carboniferous rock
sequences
Representative Lower Silurian rock sequences
Representative Upper Carboniferous rock
sequences
Devonian and Carboniferous fossil plants
Devonian ‘water scorpion’ fossils
Devonian fossil fish
Rare and unusual minerals
Quaternary stratigraphy and geomorphology; Late
glacial and Holocene sea level changes; patterns of
Late-glacial and Holocene vegetation and
environmental change
Large coastal forelands, including exceptional
examples of sand dunes; rock coast landforms and
shore platforms
Excellent example of outwash terraces,
palaeochannels and gully erosion
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the Eastern Lowlands are summarised in Table 16.2. However, there is no
systematic information on current impacts or trends.
Page 217
10 January, 2002
Table 16.2 Potential pressures and vulnerability of Earth heritage interests in the Eastern Lowlands
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting, coastal defence, quarry
infill and afforestation
Vulnerable to irresponsible collecting
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land managemen changes; construction of tracks;
afforestation; river management
Vulnerable to drainage of bogs and peat extraction
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management
changes; construction of tracks; afforestation; coast defences
Generally robust to all but large-scale developments such as
superquarries
Vulnerable to coast protection; commercial and coastal
forelands, saltmarshes, industrial developments, recreation
pressures and mudflats, land claim and sea level rise
Generally robust
Vulnerable to river engineering and management;
afforestation; gravel extraction; land management changes
Vulnerable to land management changes, pollution and loss by
erosion/hard development
Palaeontological interests
Mineralogical interests
Quaternary depositional landforms
and exposures
Palaeoenvironmental records
Records of sea level change,
including carse
Rock coast features
Beach and dune systems,
Estuarine morphology
Fluvial geomorphology
Soils
8
•
•
•
•
•
•
•
•
•
•
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Many of the palaeontological sites, particularly the vertebrate site, show evidence of
being collected from. At Granton Shore in 1985 the most fossiliferous sections of the
Granton ‘shrimp bed’ were removed to protect fossils of the conodont animal after
theft of several square metres of the bed in 1984 by a commercial collector. In 1992 a
large portion of the Cheese Bay ‘shrimp bed’ was excavated and removed by a fossil
collector; this resource will not survive another collector excavation on the same scale.
Damage to pollen sites through drainage (Black Loch).
Sand and gravel quarrying (e.g. Teith valley, NE Fife) with significant loss of landforms.
Loss of many raised bog sites through drainage and agricultural improvements.
Irresponsible fossil collecting continues to be a problem.
Further sand and gravel quarrying presents a potential threat to landform integrity.
Soil contamination, erosion and decline in quality from intensive agriculture and urban
development.
Approximately 50% of the original inter-tidal saltmarsh and mudflat in the Forth Estuary
has been ‘lost’ through land claim
The wide extent of coastal erosion and relative intensity of coastal development in this
zone has led to extensive coastal defence construction and hence stabilisation of
naturally dynamic landforms.
Page 218
10 January, 2002
9
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Region 4.South-eastt Scotland: Montrose to Eyemouth. Joint Nature
Conservation Committee, Peterborough.
Cameron, I.B. and Stephenson, D, 1985. British Regional Geology: The Midland Valley of Scotland (third
edition). British Geological Survey (HMSO, London).
Cleal, C.J. and Thomas, B.A. (1995) Palaeozoic Palaeobotany of Great Britain. Geological Conservation
Review Series No. 9. Joint Nature Conservation Committee, Peterborough.
Cleal, C.J. and Thomas, B.A. (1996) British Upper Carboniferous Stratigraphy. Geological Conservation
Review Series No.11. Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. GCR Series No. 16. Joint Nature
Conservation Committee, Peterborough.
Firth, C.R., Collins, P.E.F. and Smith, D.E. (1997) Coastal Processes and Management of Scottish Estuaries. IV.
The Firth of Forth. Scottish Natural Heritage Review No. 87.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage Commissioned
Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Gregory, K.J. (1997) Fluvial Geomorphology of Great Britain. Geological Conservation Review Series No.
13. Chapman and Hall, London.
HR Wallingford, 2000. Coastal Cells in Scotland. Cell 1 – St Abb’s Head to Fife Ness. Report to Scottish
Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and Historic
Scotland. SNH RSM Report No. 143. Battleby.
HR Wallingford, 2000. Coastal Cells in Scotland. Cell 2 – Fife Ness to Cairnbulg Point. Report to Scottish
Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and Historic
Scotland. SNH RSM Report No. 144. Battleby.
MacGregor, A. R. (1996) Fife and Angus Geology. The Pentland Press, Edinburgh.
May, V. and Hansom, J.D. in press. Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
McManus, J. and Wal, A. (1996) Sediment accumulation mechanisms on the Tentsmuir coast. In
Whittington, G. (ed) Fragile Environments: The Use and Management of Tentsmuir National Nature
Reserve, Fife. Scottish Cultural Press, Edinburgh, 1–15.
Posford Duvivier, 1998. Shoreline Management Plan of Fife. Unpublished report to Fife Council (3
volumes). June 1998. Fife Council, Glenrothes.
Posford Duvivier, 1998. St Abb’s Head to The Tyne Shoreline Management Plan. Unpublished report to
Wansbeck Council.
Rafaelli, D. (1992) Conservation of Scottish estuaries. Proceedings of the Royal Society of Edinburgh, 100B,
55–76.
Ramsay, S. and Dickson, J.H. (1997) Vegetational history of central Scotland. Botanical Journal of Scotland,
49, 141–150.
Ritchie, W. (1979) The Beaches of Fife. Countryside Commission for Scotland, Perth.
Rose, N. (1980) The Beaches of South-east Scotland. Countryside Commission for Scotland, Perth.
Saiu, E.M. and McManus, J. (1998) Impacts of coal mining on coastal stability in Fife. In Hooke, J. (ed.)
Coastal Defence And Earth Science Conservation. The Geological Society, London, 58–66.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press. 335pp.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Wright, R. (1981) The Beaches of Tayside. Countryside Commission for Scotland, Perth.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 16, 17, 18, 25, 26, 31, 32, 33, 34, 39, 40, 41, 47, 48, 49,
56, 57, 66, 67.
Page 219
10 January, 2002
Soil Survey of Scotland Maps: 1:250,000 sheets 5 and 7 and 1:63,360 sheets 66, 57, 48, 49, 40, 41, 32, 33,
and 34 cover most of the Eastern Lowlands. MLURI, Aberdeen.
Page 220
10 January, 2002
ZONE 17
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
WEST CENTRAL BELT
Highlights
Ordovician and Silurian stratigraphy provide crucial evidence for the existence and
closure of the Iapetus Ocean, and that Scotland was once part of North America.
Devonian sedimentary sequences.
Carboniferous sedimentary sequences.
One of the worlds most important Carboniferous-age shark faunas.
Some of the world’s oldest known reptile remains.
Some of the world’s oldest known terrestrial arthropods.
The only known plant assemblage from the Lower Permian of Britain.
Glaciated lowland hills and uplands.
The former presence of sites with interstadial deposits and terrestrial macrofaunal
remains.
Type area for the Loch Lomond Readvance and Loch Lomond Stadial, with an associated
suite of landforms and stratigraphy.
Drumlin landscapes including superimposed drumlins.
Nationally important glaciofluvial landforms.
Type area for the ‘Clyde Beds’.
Representative records of Late-glacial and Holocene palaeoenvironmental change,
including forest history and human impacts on the landscape.
Good examples of features associated with changes in relative sea level, including raised
platforms, cliffs and coastal progradation.
Exceptional extent inland of raised shore platform and beach deposits.
Excellent examples of river meanders and glacial diversion of drainage.
Geology
The Midland Valley is a rift valley, formed about 350 million years ago as the area now
occupied by the Midland Valley slipped down between the Highlands and the Southern
Uplands (along the Highland Boundary Fault and the Southern Upland Fault). The Midland
Valley represents one of several distinct crustal fragments that were brought together 400
million years ago, during the geological union of Scotland and England. Most of the rocks in
the Midland Valley were deposited during the Carboniferous Period, 360–300 million years
ago, and comprise coal measures, limestones, grits, sandstones, shales and mudstones. The
Carboniferous sequences have been of fundamental importance in the economic
development of Scotland.
The Midland Valley is, in general, covered by a thick mantle of drift deposits that bear little
relation to the underlying geology. The soils developed are generally widely distributed with
indistinct boundaries, and do not reflect the complexities of the underlying geology. There
is, however, a close relation between rock type, geological structures and landforms.
The sediments form low-lying areas and are punctuated by several igneous intrusions and
horizons (e.g. the Heads of Ayr). These igneous rocks tend to be more resistant to erosion
than the sediments, and so form many of the conspicuous hills and laws of the Midland
Valley (e.g. Dumbarton Rock). Often they are basalt, but some are granite or more unusual
rock types. Many of the basalts are alkali basalts, rich in potassium, yielding nutrient-rich
Page 221
10 January, 2002
soils and give rise to several ‘Green Hills’ that represent the vents of ancient volcanoes,
especially in Ayrshire.
Evidence for major tectonic activity corresponding to the closure of the Iapetus Ocean is
dramatically illustrated by the oldest rocks in the zone, which occur around Ballantrae. Here
Ordovician rocks form part of an ophiolitic assemblage (a segment of oceanic crust)
comprising serpentinite, pillow lavas and cherts, associated with mudstones, conglomerates,
sandstones and graptolitic schists. Elsewhere, late Ordovician sediments occur (e.g. Stinchar
limestone), together with conglomerate, mudstones and sandstone. A number of these
outcrops contain important faunas (see below). The Corsewall conglomerate contains
granite clasts that may be derived from intrusions in Newfoundland, thus providing evidence
of considerable strike-slip movement prior to Scotland’s accretion. Silurian beds at Girvan
and Craighead provide crucial evidence that Scotland was once part of the North American
continent and that the Iapetus Ocean separated Scotland from England.
For the most part, the zone reflects the results of crustal instability and changing
depositional environments during the Devonian and Carboniferous Periods. The
environment during the Devonian, which began about 400 million years ago and ended at
the start of the Carboniferous Period, around 360 million years ago, consisted of deserts
and rivers. Sediment, comprising cobbles, gravel, sand and finer material including silt and
mud, derived from the Caledonian mountains to the north and the newly emergent
Southern Uplands to the south, was deposited in this desert environment which formed a
low-lying ‘basin’. Much of the Devonian outcrop is found in the north of the zone, adjacent
to the Highland Boundary Fault and west to Wemyss Bay, and in the south of the zone,
around Maybole and Straiton. The sediments in the north consist predominantly of
sandstone, with conglomerates in the east, and mudstones towards the top of the sequence.
These sediments are valuable palaeogeographic and palaeoenvironmental indicators,
providing evidence of the existence of high-ground around the Midland Valley. The
Devonian succession is interspersed with volcanic rocks, the igneous activity being indicative
of unstable crustal conditions that persisted after the closure of the Iapetus Ocean. Principal
outcrops form the Carrick Hills, the area around Straiton and a granodiorite intrusion south
of Darvel. These rocks are largely basic to intermediate in character, although some acid
rocks also occur.
A thick succession of Carboniferous rocks occurs in the zone, spanning the full 60 million
years of this geological period, which saw Scotland drift from approximately 15°S of the
equator to equatorial latitudes. The Carboniferous saw an increasing marine influence and
cyclic sedimentation led to the formation of deltas, swamps, lagoons and shallow marine
conditions. Consequently, the Carboniferous sequence comprises a greater variety of rock
types than the Devonian: limestone, coal, sandstones, siltstones and mudstones. The
Carboniferous is subdivided into the Lower and Upper Carboniferous, commonly referred
to as the Dinantian and Silesian respectively. Principal exposures of Lower Carboniferous
rocks occur east of Girvan and Cumnock, and around Johnstone and Milngavie.
Cementstones, oil-shales and non-marine limestones occur at the base of the Lower
Carboniferous, with marine limestones and mudstones occurring throughout the upper part
of the Lower Carboniferous succession.
The Central and Ayrshire Coalfields represent Upper Carboniferous rocks. The lower part
of these sequences consists of sandstones, siltstones and mudstones with coals and seatearths. The Limestone Coal Group, which forms the lower part of the Silesian sequence,
Page 222
10 January, 2002
and the Coal Measures at the top of the sequence have formed much of the focus for the
Scottish coal-mining industry.
The sediments of the Carboniferous are interspersed with volcanic rocks and igneous
intrusions associated with crustal instability. Glasgow is surrounded on three sides by
extensive lava fields that form the Renfrewshire Hills, the Kilpatrick Hills, the Campsie Fells
and Gargunnock Hills. These are associated with numerous vents, aligned along principal
faults. Later, Upper Carboniferous lavas occur east of Ardrossan and south to Ayr.
Numerous dolerite intrusions occur west of Galston and in the Glasgow area (e.g. seen in
road cuttings at Milngavie). The Midland Valley sill forms an arcuate series of exposures
from Stirling to Shotts in the south, forming prominent scarp features. Permian lavas occur
around the edge of the Mauchline basin.
The Mauchline basin contains Permo-Triassic red sandstones and mudstones. These
comprise windblown desert sandstones and their presence in the area is an important
palaeogeographic and palaeoenvironmental indicator.
3
Palaeontology
The oldest fossils in the Zone are the 480-million-year-old, single-celled marine protozoans
of the Lower Ordovician. They form a rock type known as radiolarian chert that developed
on the floor of the Iapetus Ocean and which is now a constituent part of the Ballantrae
Complex. The Girvan Sedimentary Cover Rock Sequence, which lies above the Ballantrae
Complex, yields a variety of deep and shallow marine faunas, which include graptolites,
trilobites, brachiopods, starfish and crinoids. The Ordovician age faunas of the Girvan area,
found at sites such as Craighead Quarry, have a distinct North-American affinity, providing
crucial evidence that Scotland was once part of North America and that England at that time
lay far to the south across the Iapetus Ocean.
Early terrestrial plant floras occur within the 390-million-year-old Lower Devonian
lacustrine–fluvial sequences in the north of the zone in the Dunbarton area. The fossil
evidence of early terrestrial life, in the form of arthropod tracks, is also found in volcanicassociated sequences on the Ayrshire coast at Dunure.
As in the rest of the Midland Valley, Lower and Upper Carboniferous sequences are very
well developed and yield a plethora of fossil faunas and floras, indicative of a multiplicity of
constantly changing environments. At Bearsden, near Glasgow, sediments deposited in an
ancient brackish-water environment, have yielded one of the world’s most important shark
faunas. Lower Carboniferous volcanic activity had an important role in the establishment of
a particularly unusual hot-spring environment in which the East Kirkton sequence near
Bathgate was deposited. This sequence has yielded a spectacular fossil ecosystem that
includes many amphibians, the earliest known reptiles and arthropods of various types.
The youngest sedimentary rocks are of Permian age and occur in Ayrshire. These have
yielded the fossil remains of a sparse, low diversity, desert flora. This is the only known
Lower Permian floral assemblage in Britain.
Page 223
10 January, 2002
4
Geomorphology
The whole zone has been modified by the effects of glacial erosion and deposition during
the Quaternary ice ages. The effects of glacial erosion are more subtle than in the Highlands.
Pre-existing valleys were over-deepened (e.g. the Clyde) but later infilled with drift, and the
hills moulded and streamlined by the passage of the ice. Particularly striking examples of
such moulding are represented in the crag and tail forms of West Lothian (e.g. Dechmont
Law). The lower ground is extensively mantled by a cover of drift deposits from the last and
earlier ice sheets, comprising variable thicknesses of till and sand and gravel. In many cases
these deposits have a range of surface forms, including drumlins (with superimposed forms
north of Glasgow), eskers, kames and outwash terraces. Notable features include the
drumlin field of the Glasgow area and the zone of glaciofluvial deposits extending NE
through Lanark, including the nationally important Carstairs Kames. Locally, extended
sequences of deposits occur, which have been critical for interpreting the glacial history of
Scotland (including sites with fossil mammal remains), notably in the Glasgow area and in
Ayrshire (e.g. Kilmaurs, Bishopbriggs, Sourlie), but few, if any, remain exposed or accessible.
Shelly tills occur in Ayrshire, indicating onshore movement of the ice. At Afton Lodge, the
occurrence of a controversial shelly clay has been used to infer former high sea levels, but
the deposit may not be in situ. The Loch Lomond area provides critical evidence for the final
episode of glaciation at the end of the ice age. The south-east part of the basin between
Balloch and Gartness is the type area in Britain both for the glacial event known as the Loch
Lomond Readvance and for the associated climatostratigraphic episode, the Loch Lomond
Stadial. This period of intense cold and renewed glaciation occurred at the end of the last
glaciation approximately between 12,600 and 11,500 years ago. The interest includes
stratigraphic sections (Croftamie) and superb assemblages of glacial, glaciofluvial and
glaciolacustrine deposits in a zone extending around the southern margins of the loch (e.g.
at Cameron Muir and in the Drymen area).
This zone also has an important record of relative sea level change in Scotland, represented
in the deposits of the western Forth Valley. In the Clyde estuary area, Clyde Beds (coldwater, fossiliferous estuarine deposits laid down during the Late-glacial) are widely
represented in their type area (e.g. at Geilston and at Claddochside on Loch Lomond,
where they are overlain by Loch Lomond Readvance till).
The coastline of the zone, particularly in the north, is relatively intensively developed
compared with most other zones, and consequently some features of potential interest have
been obscured.
The most distinctive and impressive aspect of the coastal topography is the pronounced
raised shore platform and cliff line, part of the Main Rock Platform described in Zone 14.
This distinctive feature extends along virtually the entire coastline from Cloch Point in the
north to Ballantrae in the south. It also occurs on the south shore of Loch Lomond (e.g. at
Ross Priory). The platform is tilted, and south of Ayr it becomes intertidal (e.g. between
Heads of Ayr and Turnberry, there are several well-developed examples). The platform and
its backing cliff line are particularly clearly formed around the Cumbraes and at Skelmorlie,
Portencross and Ballantrae on the mainland. Towards Ballantrae, in particular, numerous
small caves and gullies delineate the foot of the fossil cliff and even occasional ancient sea
stacks rest upon the raised shore platform.
The platform is frequently overlain by extensive raised beach deposits that, around
Prestwick and Irvine, extend 4–5 km inland from the present-day coast, thereby indicating
Page 224
10 January, 2002
rapid coastal progradation that has taken place in this area in the last 5,000–6,000 years.
Raised marine landforms and deposits also extend into the southern part of Loch Lomond,
indicating that the loch formed an arm of the sea at different times in the past.
Present-day shorelines of this zone are dominated by sandy beaches and dunes particularly
around Turnberry, Maidens and between the Heads of Ayr and Seamill. Cliffs are rare but
locally impressive as, for instance, around Culzean. Elsewhere, beaches are dominated by
sand, gravel and low rocky shore platforms. A particularly extensive shingle bar has
developed across the mouth of the Stinchar Water, south of Ballantrae, which is over 1.5
km in length. In the comparative shelter of the Clyde estuary, upstream of Langbank,
mudflats and saltmarshes are the dominant landforms.
The Late-glacial and Holocene vegetation history has been studied in detail at a number of
sites in the zone. Of particular interest are the contrasting records between sites that lay
within the limits of the Loch Lomond Readvance and those immediately outside, as in the
Callander area. The application of multi-proxy approaches has elucidated considerable detail
about the environmental changes during the Late-glacial, and the recognition of volcanic ash
layers in the sediments has allowed greater stratigraphic resolution, as at Tynaspirit in the
Teith valley. During the middle Holocene, the predominant woodland type in the zone was
oak. The pollen records from the northern part of the zone provide important insights into
the vegetation history of the ecotone between the mixed deciduous woodlands of the
lowlands and the pine woods of the Highlands.
The zone contains the headwaters of rivers draining east (tributaries of the Forth, including
the River Almond, River Avon, River Carron and the Water of Leith), as well as many rivers
draining west from the central watershed into the Clyde estuary. Much of the zone can be
classed as lowland, and even the upland headwaters are also of relatively gentle relief. In
consequence, the rivers have similar meandering or sinuous planforms and have fine sand or
silty material in transport. They change channel planform downstream and channel position
through gradual cutting back of banks at meander bends.
To the north of the Clyde Estuary, the major rivers are the Endrick Water, the River Leven
and the River Kelvin. The Endrick Water meanders for much of its course, particularly
below Drymen Bridge, where palaeochannels, meander scrolls and a dated cut-off make it a
key site for studies of floodplain development. The River Kelvin also has a sinuous course
but has been subject to engineering under the recently repealed Land Drainage (Scotland)
Scheme. Cut-offs from former channels remain on the floodplain as evidence of higher past
rates of channel activity.
The Clyde is mainly sinuous in its lower reaches and has a number of lowland tributaries
within this zone. Like the River Kelvin, the lower reaches of the Clyde have been subject to
repeated dredging. To the south of Lanark, the Clyde includes an excellent example of
glacial diversion of drainage. Here the present course of the river occupies a bedrock gorge
that was cut following the infilling of its former course by glacial deposits. The gorge section
includes two spectacular waterfalls, and is a fluvial geomorphology SSSI and GCR site.
The rivers draining to the west coast south of the Clyde Estuary also meander (e.g. the
Irvine, Ayr, Garnock and Annick Water), particularly in their lower reaches, which may be
related to the progradation of the coast described above.
Page 225
10 January, 2002
5
Soils
Finer-textured drift materials and high rainfall have resulted in a high proportion (51%) of
gleyed soils with excess surface moisture characteristics. This zone also has tills and
glaciofluvial deposits derived from calcareous sandstones, so that brown earth soils are
relatively common (23% of the total soil resource). In areas where topography and climate
allow, peat accumulation has occurred and extraction of this resource has been extensive.
Soils with national significance include anthropogenically deepened (‘plaggen’) soils
associated with long cultivation practice on the raised beach sands on the Ayrshire coast,
and mature oakwoodland brown earths on the Loch Lomond islands which are quite rare in
Scotland. A significant proportion of soils (12% of the soil resource) have been truncated or
removed for urban development, and many soils have been contaminated by past and
present industrial and mining activity. Significant areas of grade 2 agricultural land are
cultivated intensively on the Ayrshire coast. As a result, they have lost original semi-natural
features and some may have been degraded by inappropriate soil husbandry. It is also likely
that many of these agriculturally valuable soils have been lost through urban development
and/or contamination. Of local significance are contaminated soils around the Glasgow area.
These sometimes support unique plant communities that are tolerant of high concentrations
of trace metals. There are many examples of reinstated soils following opencast coal mining.
Localised soil erosion arising from inappropriate cultivation practices also occurs, but the
extent has not been determined.
6
Summary of key Earth science features in the West
Central Belt
The principal Earth heritage interests in West Central Belt are summarised in Table 17.1.
The West Central Belt includes a total of 58 GCR sites.
Page 226
10 January, 2002
Table 17.1 GCR sites in West Central Belt
GCR block
No. of sites
Principal interests
Caradoc–Ashgill
4
Ordovician Igneous
Llandovery
10
3
Arenig
1
Non-marine Devonian
1
Old Red Sandstone Igneous
Permian-Carboniferous
1
2
Ordovician palaeogeography and palaeoenvironment
reconstruction
Evidence for the Iapetus Ocean and its closure
Silurian palaeogeography and palaeoenvironment
reconstruction
Odovician palaeogeography and palaeoenvironment
reconstruction
Devonian palaeogeography and palaeoenvironment
reconstruction
Wet sediment and lava interaction
Internationally significant early Carboniferous faunas
fish/amphibia
Volcanic activity during the Carboniferous
Early Carboniferous palaeogeography/environmental
reconstruction
Late Carboniferous palaeogeography/environmental
reconstruction
Internationally significant floral assemblages
Internationally significant arthropod assemblage
Carboniferous volcanic features and minerals
Type area for Loch Lomond Readvance, classic
glaciofluvial landforms, high-level shelly clays, type
area for Clyde Beds, Holocene sea level changes
River meanders and waterfalls
Permo-Carboniferous Igneous 7
Dinantian
15
Westphalian
1
Palaeozoic Palaeobotany
Arthropoda
Mineralogy
Quaternary of Scotland
5
1
1
9
Fluvial Geomorphology
2
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the West Central Belt are summarised in Table 17.2. However, there is no
systematic information on current impacts or trends.
Page 227
10 January, 2002
Table 17.2 Potential pressures and vulnerability of Earth heritage interests in the West Central Belt
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction, infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; river management
Vulnerable to drainage of bogs and peat extraction
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Vulnerable to river engineering and management;
afforestation gravel extraction; land management changes
Vulnerable to land management changes, pollution
Palaeontological interests
Quaternary depositional landforms
and exposures
Palaeoenvironmental records
Records of sea level change
Fluvial geomorphology
Soils
8
•
•
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Fossils are collected from the fossiliferous exposures.
Extensive sand and gravel quarrying has destroyed many glaciofluvial landforms in the
zone e.g. in Lanarkshire.
Loss of soils through urban and industrial development, contamination, opencast mining,
and localised erosion (Gauld and Puri, 2000).
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Region 14. South-west Scotland: Ballantrae to Mull. Joint Nature
Conservation Committee, Peterborough
Bluck, B. J. (1971) Sedimentation in the meandering River Endrick. Scottish Journal of Geology, 7, 93–138.
Bown, C.J., Shipley, B.M. and Bibby, J.S. (1982) Soil and Land Capability for Agriculture. South-West Scotland.
Aberdeen, The Macaulay Institute for Soil Research.
Cameron, I.B. and Stephenson, D, 1985. British Regional Geology: the Midland Valley of Scotland (third
edition). British Geological Survey (HMSO, London).
Cleal, C.J. and Thomas, B.A. (1995) Palaeozoic Palaeobotany of Great Britain. Geological Conservation
Review Series No. 9, Joint Nature Conservation Committee Peterborough.
Cleal, C.J. and Thomas, B.A. (1996) British Upper Carboniferous Stratigraphy. Geological Conservation
Review Series No.11, Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. Geological Conservation Review Series
No. 16, Joint Nature Conservation Committee Peterborough.
Firth, C.R. and Collins, P.E.F. (2000) Coastal Processes and Management of Scottish Estuaries. VI. The Firth of
Clyde. Unpub. Report to Scottish Natural Heritage.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage Commissioned
Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Gregory, K.J. (1997) Fluvial Geomorphology of Great Britain. Geological Conservation Review Series, No.
13. Chapman and Hall, London.
Page 228
10 January, 2002
HR Wallingford, 2000. Coastal Cells in Scotland. Cell 6 – Mull of Kintyre to Mull of Galloway. Report to
Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and
Historic Scotland. SNH RSM Report No. 148. Battleby.
Lawson, J.D. and Weedon, D.S. (1992) Geological excursions around Glasgow and Girvan. Geological
Society of Glasgow.
Mather, A.S. (1979) Beaches of South-west Scotland Volume I. Dept. of Geography, University of Aberdeen.
Countryside Commission for Scotland. Perth.
May, V. and Hansom, J.D. in press. Coastal Geomorphology of Great Britain. Geological Conservation
Review Series 24. Joint Nature Conservation Committee, Peterborough.
Rafaelli, D. (1992) Conservation of Scottish Estuaries. Proceedings of the Royal Society of Edinburgh, 100B,
55–76.
Ramsay, S. and Dickson, J.H. (1997) Vegetational history of central Scotland. Botanical Journal of Scotland,
49, 141–150.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Simpson, J.B. and MacGregor, A.G. (1949) The Geology of Central Ayrshire.
Memoir of the Geological Survey of Scotland (HMSO, Edinburgh).
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17, Joint Nature
Conservation Committee Peterborough.
Ting, S.1937. Storm waves and shore-forms of south-western Scotland. Geological Magazine, 74,
132–141.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 7,8,14,15,22,23,24,30,31 and 38
Soil Survey of Scotland Maps: 1:250,000 sheet 6 and coloured 1:63,360 sheets 31, 23, 22, 30 and 14
cover most of the West Central Belt. MLURI, Aberdeen.
Page 229
10 January, 2002
ZONE 18
1
•
•
•
•
•
•
•
•
•
•
2
WIGTOWN MACHAIRS AND OUTER SOLWAY
Highlights
Location of the Iapetus Suture.
Sections through the Southern Uplands accretionary wedge.
Ordovician and Silurian sedimentary sequences.
Fold structures that reveal much about the Caledonian Orogeny.
Caledonian plutonic and volcanic rocks.
Carboniferous sedimentary sequences marking the northern edge of the
Solway–Northumberland basin.
Good example of drumlins.
Largest beach–dune system in south-west Scotland
Excellent examples of estuarine saltmarsh.
Extensive occurrence of raised platform and cliff line.
Geology
This zone is almost entirely underlain by sedimentary rocks that were laid down in a wide
range of environments over a 200-million-year period of Earth history. The oldest rocks
date from the Ordovician Period around 460 million years ago. These, together with
younger Silurian rocks, represent the south-eastern margin of the Southern Uplands and
extend into the neighbouring Zones 19, 20 and 16.
Representing the basic framework of the zone, the Ordovican and Silurian rocks were
originally sands and muds that floored the Iapetus Ocean. Deposited over a 70-million-year
period, these rocks bear testimony to the closure of the ocean with the coming together of
what is now the North American continent and Northern Europe, as a result of the joining
of the crustal foundations of both Scotland and England. The ‘Iapetus Suture’, which marks
the generally recognised zone of closure of the ancient ocean, occurs just to the south of
the zone and runs along a NE–SW line that follows the line of the Solway and the
Scotland–England border. At the north-western tip of the zone, running in a similar NE–SW
line, the Southern Uplands Fault marks the northern limit of the southern Uplands and its
contact with the Midland Valley
The ancient sands and muds of the zone can be grouped in terms of age into two major
NE–SW-running units, with the older Ordovician rock layer sequences occurring to the
north and west of Stranraer, at the Southern Upland Fault, and the younger Silurian
sequences, comprising the bulk of the zone, to the south and east. Within these two major
subdivisions there are several further subdivisions and much evidence of rock layer folding
and faulting. Localities such as Back Bay, near Monreith, Grennan Bay and the Isle Whithorn
display visually spectacular ‘text-book’ examples of rock folds and other structures. The fold
structures at Back Bay not only illustrate two fold generations with a second set of folds
superimposed upon first, but are of particular significance in representing the one of the
most dramatic large-scale exposures of major refolded folds anywhere in the UK.
By using fossils known as graptolites, a now extinct group of colonial plankton organisms, and
through the application of plate tectonic theory to the rock folds and faults, the structure
and origin of the Southern Uplands has largely been determined. A very elegant model now
explains how the muds (black shales) and sands (greywackes) of the Southern Uplands
Page 230
10 January, 2002
represent marine sediments that were scraped off the floor of Iapetus to form a wedgeshaped package (accretionary wedge). This was heaped onto the northern continent, as the
continents carrying England and Scotland collided and the ocean between them closed. This
collision also affected much of what was to become Scotland and is known as the
Caledonian Orogeny, or mountain-building event.
During the final stages of the Caledonian deformation, there was the widespread intrusion
of felsite and microdiorite dykes across the zone. However, the climax of igneous activity
was reached as deformation of the sediments ended, with the intrusion of major granite
plutons, around 400 million years ago at the start of the Devonian period. The granite in
these masses was derived from the actual partial melting of rocks lower within the crust,
where the heat and deformation caused by the continental collision was most intense. The
melting resulted in the formation of great masses of silica-rich melt that moved upwards
through the crust and which became emplaced within the Ordovician and Silurian
sediments. The heat given out by the cooling plutons, as they are known, locally baked, or
contact metamorphosed, the surrounding sediments, producing honrfelsed rock. The
hornfelsing effect extended for a kilometre or more outwards from the largest plutons. The
largest pluton in the Southern Uplands, the Criffell granite, underlies the eastern margin of
the zone. A much smaller pluton occurs on the Mull of Galloway, west of Drummore. At
Shoulder O’Craig near Kirkcudbright, there is an early Devonian volcanic vent that cuts up
through Silurian rocks. This is the largest and best-exposed example in SW Scotland of a
late Caledonian volcanic vent and is important in respect of the models for the closure of
the Iapetus Ocean.
Along the coastal strip between Abbey Head and Balcary Point, sedimentary rocks of Lower
Carboniferous age occur, resting with an unconformity upon Silurian sediments of the
accretionary wedge. These were laid down at the northern margin of the
Solway–Northumberland Basin, a low-lying area that formed in Devonian and Carboniferous
times following the Caledonian Orogeny. The sand, silt and mud that comprises the bulk of
the sediment deposited in the Solway Basin was derived through the erosion of the
Southern Uplands, which at the time would have been a considerably higher range of
mountains. Within the basin, which was entirely separated from the Midland Valley Basin to
the north, a multiplicity of environments from shallow marine to coastal plain existed
through time as the relative levels of sea and land changed. Limestones, a significant
component of the Carboniferous sequence of the basin, were formed through the
accumulation of animal shells and skeletons and by chemical precipitation from the tropical
sea water.
Towards the end of Lower Carboniferous times, erosion led to the lowering of the
Southern Uplands to such an extent that they were breached by the sea, and the Midland
Valley and Solway Basins were linked. It is thought that at this time there might have been
wider Carboniferous sediment deposition across the area but that has now been eroded.
Within the zone, a small patch of Upper Carboniferous ‘Coal Measures’ sediment on the
western side of Loch Ryan is testimony to a much greater coverage of Carboniferous
sedimentary rocks over the underlying Ordovician and Silurian. Crustal shortening, and a
process known as ‘basin inversion’, took place in the Solway during late Carboniferous
times, resulting in the gentle deformation of the Lower Carboniferous sediments.
By Permian times, the climate had changed from semi-tropical and tropical to arid, and the
low-lying basins evident in the Carboniferous had started to subside again. Within these
Page 231
10 January, 2002
‘rejuvenated’ basins, sediment again accumulated, although in a fully terrestrial rather than
the marine or coastal plain environments typical of the Carboniferous. The western side of
Loch Ryan and the ‘isthmus’ to the south are underlain by fluvial sands and silts in addition
to sand dune, or aeolian, deposits laid down in Permian desert environmental conditions.
3
Palaeontology
Deep marine Ordovician and Silurian sediments, representing a portion of an accretionary
wedge on the edge of Iapetus, yield a fossil marine fauna, consisting largely of graptolites.
These fossils are invaluable as stratigraphic markers and have allowed the development of
models explaining the evolution of southern Scotland.
Lower Carboniferous sediments, forming a southern basin of sedimentation distinct from
the Midland Valley, yield a characteristic suite of shallow marine and estuarine fossil faunas.
4
Geomorphology
This area comprises the Rhins of Galloway and the southern parts of the peninsulas to the
east. The low hills are generally drift covered, commonly with drumlins.
In the Rhins, there are possibly the only known examples of the Errol Beds (see Zone 16)
onshore in western Scotland.
The coastline of this zone is predominantly a rocky one, albeit incised by a number of deep
bays and estuaries where more sheltered conditions prevail and within which sandflats and
saltmarshes have accumulated. Cliffs are most extensive and best developed along the
exposed shore of The Rhins and culminate at 120 m in height near Dunman. This cliff line is,
however, largely inactive at present times having been raised clear of wave action by
isostatic uplift since the end of the Ice Age. Traces of this raised cliff line and a raised beach
in front are manifest around most of the coastline of this zone and, on the eastern side of
Luce Bay and western shore of Loch Ryan, clearly show a range of small gullies and caves at
their junction.
In contrast to these largely relict landforms, the massive beach dune complex of Torrs
Warren-Luce Sands is a highly dynamic and still actively accreting system. This is the largest
beach–dune system in south-west Scotland and contains a complex array of dune-related
landforms as well as saltmarsh and raised Holocene beach ridges.
At Wigtown, Gatehouse of Fleet and Kirkcudbright, narrow estuarine bays split the outer,
rocky coastline. Wide expanses of sandflat, mudflat and saltmarsh have developed within
these bays, reflecting the more sheltered conditions which prevail there, as well as the
ample sediment supply which they receive. Of these deposits, the saltmarshes of the Cree
estuary at Wigtown are especially well developed and have been listed in the GCR for the
range of saltpans and tidal creeks which they contain.
Outwith these specific areas, the coastline of this zone is dominated by rocky shores and
low cliffs, locally enclosing small pocket beaches or fronted by impersistent stretches of sand
and shingle.
Page 232
10 January, 2002
The second-order streams on the Rhins of Galloway drain predominantly to the east, with
only short first-order burns draining to the rocky western coast. The low, drift-covered hills
generate rivers with mainly sinuous or meandering planforms and occasional lochs and bogs.
The Piltanton Burn flows into Luce Bay, draining a large, low, relatively flat catchment. The
lower-middle reaches show evidence of having been straightened (with the parish boundary
diverging from the currently straight channel) and the burn ends in a delta with evident
irregular meanders and cut-offs. The main stems of the large rivers draining to the estuarine
bays at Fleet (Water of Fleet), Kirkcudbright (River Dee) and Luce Bay (River Luce) are
outside the zone and only the lower reaches of the larger River Cree and the River
Bladnoch are within Zone 18. The River Bladnoch drains south-east from Dumfries and
Galloway into Wigtown Machairs. The lower reaches meander irregularly and tortuously,
and occupy a large meander train. Many of the bends have been embanked to prevent
flooding of the adjacent land. The lower reaches of the River Cree and the majority of the
Bishop Burn also meander tortuously within the zone.
Dowalton Burn (which drains west into Garlieston Bay) has been straightened along much
of its course, whereas the Monreith Burn (which drains south-west) is mainly sinuous but
follows the edge of the Fell of Barhullion requiring it to take a circuitous route (turning 180
degrees) to the sea at Monreith Bay. The rivers in the peninsulas to the east and west of
Kirkcudbright Bay are generally aligned NE–SW, with some limited evidence of standing
water. Flowing towards low rocky cliffs, the rivers and burns are relatively straight, ending in
small coastal waterfalls or rocky inlets.
5
Soils
Soil parent materials are primarily Pleistocene drift deposits and postglacial deposits that are
often complex in nature. Soil diversity is high, particularly in the areas where drumlins are
common and there are complex soil patterns associated with these features. The higher
base status of parent materials in this zone, combined with limited topographic and climatic
constraints, has led to the development of primarily brown earth soils (44%) with higher
potential fertility. Surface-water gleys are also common (41%), found in areas where soils
have formed on finer-textured materials with impeded drainage; some of these have been
drained and converted to agricultural usage. There are very few podzols (2%), and where
drainage is impeded and decomposition is slow local peat deposits are found. Most of the
soils in this zone have been cultivated over a long time and the diversity of soils is high,
despite many years of intensive cultivation.
6
Summary of key Earth science features in Wigtown
Machairs and Outer Solway
The principal Earth heritage interests in Wigtown Machairs and Outer Solway are
summarised in Table 18.1. Wigtown Machairs and Outer Solway includes a total of 12 GCR
sites.
Page 233
10 January, 2002
Table 18.1 GCR sites in Wigtown Machairs and Outer Solway
GCR block
No. of sites Principal interests
Caledonian Igneous
1
Caledonian Structures of
Southern Uplands
Wenlock
Quaternary of Scotland
Coastal Geomorphology
6
7
2
1
2
Igneous rocks formed as a result of the Caledonian
Orogeny
Fold structures formed during the Caledonian
Orogeny
Representative Middle Silurian rock sequences
Representative site for glacial deposits
Dynamic beach–dune complex and saltmarshes
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in Wigtown Machairs and Outer Solway are summarised in Table 18.2.
However, there is no systematic information on current impacts or trends.
Table 18.2 Potential pressures and vulnerability of Earth heritage interests in Wigtown Machairs
and Outer Solway
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Palaeontological interests
Vulnerable to mineral extraction, infilling of quarries; vulnerable
to irresponsible collecting
Quaternary depositional landforms Vulnerable to mineral extraction/quarrying; commercial, and
exposures industrial and infrastructure developments; land
management changes; construction of tracks; afforestation; river
management
Rock coast features
Generally robust to all but large scale developments such as
superquarries
Beach–dune complex
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes; construction
of tracks; afforestation; coast defences
Saltmarshes
Vulnerable to coast protection/land claim, sea level rise
Fluvial geomorphology
Vulnerable to river engineering and management; afforestation;
gravel extraction; land management changes
Soils
Vulnerable to land management changes, pollution
8
•
•
•
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Sea level rise may have a greater impact in this zone than in more central parts of
Scotland.
Fossils are collected from the fossiliferous exposures.
Page 234
10 January, 2002
9
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1996) Coasts And
Seas Of The United Kingdom. Region 13. Northern Irish Sea: Colwyn Bay to Stranraer including the Isle of
Man. Joint Nature Conservation Committee, Peterborough
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1997) Coasts And
Seas Of The United Kingdom. Region 14. South-west Scotland: Ballantrae to Mull. Joint Nature
Conservation Committee, Peterborough
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Creig, D.C. (1971) British Regional Geology: The South of Scotland (third edition). British Geological Survey
(HMSO, London).
Firth, C.R., Collins, P.E.F. and Smith, D.E. (1999) Coastal Processes and Management of Scottish Estuaries. V.
The Solway Firth. Scottish Natural Heritage Review No. 128.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage Commissioned
Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
HR Wallingford, 2000. Coastal Cells in Scotland. Cell 6 – Mull of Kintyre to Mull of Galloway. Report to
Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and
Historic Scotland. SNH RSM Report No. 148. Battleby.
HR Wallingford, 2000. Coastal Cells in Scotland. Cell 7 – The Solway Firth. Report to Scottish Natural
Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and Historic Scotland. SNH
RSM Report No. 149. Battleby.
Mather, A.S. (1979) Beaches of South-west Scotland Volumes I and II. Dept. of Geography, University of
Aberdeen. Countryside Commission for Scotland. Perth.
May, V. and Hansom, J.D. in press. Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Single, M.B. and Hansom, J.D. (1994) Torrs Warren – Luce Sands SSSI: Documentation and Management
Prescription. Scottish Natural Heritage RSM Report No. 13.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Tipping, R.M. (1999) The Quaternary of Dumfries and Galloway. Field Guide. London, Quaternary Research
Association.
Treagus, J.E. (1992) Caledonian Structures in Britain South of the Midland Valley. Geological Conservation
Review Series No. 3. Joint Nature Conservation Committee, Peterborough.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 1, 2, 3, 4, 5, 7.
Soil Survey of Scotland Maps: 1:250,000 sheet 6 encompasses Zone 18 and colour 1:63,360 sheets 1, 2,
3, and 4 cover the Wigtown Machairs. MLURI, Aberdeen.
Page 235
10 January, 2002
ZONE 19
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
WESTERN SOUTHERN UPLANDS AND INNER
SOLWAY
Highlights
Ordovician and Silurian stratigraphy provides a palaeoenvironmental record of the
northern margin of the Iapetus Ocean and helps to elucidate the structural deformation
of the Southern Uplands.
Carboniferous rock sequences provide a palaeoenvironmental record of marine and
delta environments on either side of the Southern Uplands.
The zone contains the type locality for the rock type lugarite and a classic example of
magmatic differentiation.
Permian–Triassic stratigraphy records desert-like conditions at the transition between
the Palaeozoic and Mesozoic eras.
The palaeontological record has been fundamentally important in establishing the
structural framework of the Southern Uplands.
Silurian elements of the fossil fauna have been crucial in studies of vertebrate evolution.
Intrusion and fracture system associated mineralisation are well demonstrated.
Leadhills is the most important lead–zinc mineral deposit in Scotland and is world
renowned.
The geology of continental collisions has progressed through examination of rocks in
this zone.
Glacial landforms and deposits include classic examples of drumlins, the only known
example of rogen moraines in Great Britain and representative examples of the Loch
Lomond Readvance moraines of the Southern Uplands; they also record the interactions
of Highland and Southern Uplands ice.
Tinto Hill includes one of best examples in Scotland of active stone stripes.
Coastal deposits record relative sea level changes in an area peripheral to main area of
isostatic uplift.
Loch deposits and bogs provide records of palaeoenvironmental change, notably the
forest history of SW Scotland and human impacts on the landscape, including industrial
pollution.
The River Clyde and its tributary, the Medwin water, provide excellent examples of
lowland river meanders, channel migration, cut-offs and cut-off infills that have been
documented over a period of 150 years.
Estuarine geomorphology, including extensive saltmarshes and mudflats noted for their
complex micro-topography.
The most extensive inter-tidal sandflats and mudflats in Scotland.
Geology
Zone 19 comprises parts of two of the major geological segments, or ‘terranes’, of Scotland:
the Midland Valley terrane and the Southern Upland terrane. (Terranes are blocks of the
Earth’s crust characterised by unique geological histories.) The junction between the two
terranes is marked by one of Scotland’s major faults: the Southern Upland Fault.
South of the fault, the geology is predominantly a thick sequence of Ordovician to Silurian
sediments, a mixture of mudstone, shales, gritstones and greywackes (poorly sorted
sandstone, with quartz and grains of other minerals in a clay matrix). These deposits
represent ocean floor sediments, formed as turbidites – underwater avalanches – in an
Page 236
10 January, 2002
ocean trench in the Iapetus Ocean. They were bulldozed by colliding continents into a giant
wedge of thrust-bounded packages, termed an accretionary prism. This process is thought
to be analogous to that taking place along present-day plate boundaries (e.g. in Japan and
western North America). Zone 19 is internationally important for illustrating the geological
features associated with two continental masses colliding. Some of the key features are
illustrated in the Ballantrae area.
On a broad scale, the nature of the rocks in the zone is very consistent, as is the NE–SW
structural trend. It is for this reason, that the Southern Uplands weather to their
characteristic smooth, rolling appearance, with the banded nature of the geological
foundation evident from the air.
After continental collision, the Southern Uplands were intruded by a series of large granitic
bodies: Criffel, Fleet and Doon. Several mineral localities are found in the zone, associated
with the granites. This zone is important for demonstrating mineralisation processes
associated not only with the igneous intrusions, but also with fracture systems produced
tectonically during the continental collision. Leadhills is a world-renowned mineral location.
It is the most important lead–zinc mineral deposit in Scotland, and was worked over a
period of 400 years.
During Devonian and Carboniferous times, Scotland as a whole drifted north towards, and
then across, the equator. Crustal extension led to the development of basins. Devonian
sandstones (river deposits) and volcanic rocks formed in these basins and occur today
adjacent to the Southern Upland Fault around Tinto Hill. The Devonian terrestrial
environment gave way, at times, in the Carboniferous to shallow marine conditions. The
resulting limestones, with delta and swamp conditions, produced today’s coal measures.
Carboniferous rocks forming part of the Solway Basin outcrop today in the south of the
zone, and small exposures, representing an extension of those of the Midland Valley, occur
around Sanquar and Thornhill. These rocks are important for allowing reconstructions of
the ancient geography and environment of the area during the Carboniferous, when much of
the mineral wealth of the zone was formed.
Subsequent crustal extension during Permian times led to the deposition of desert
sandstones, now preserved around Thornhill, Dumfries and Lochmaben. These rocks are
important for their fossil remains (see below) and also continue to be an important source
of dimension stone.
To the north of the Southern Upland Fault, the outcrop pattern of the geology is not so
simple and is dominated by a mixture of Devonian sandstones and Carboniferous sediments
and intrusions. However, small pockets of older Silurian rocks occur as inliers, for example
at Lesmahagow and Hagshaw Hills. These are significant exposures, containing important
fossil fish and arthropods. Although of Silurian age, these rocks provide palaeogeographic
and environmental evidence for the transition between marine and terrestrial conditions in
southern Scotland as the Iapetus Ocean finally closed.
The crustal instability during the Carboniferous and Permian times also led to melting in the
mantle. Magma rose through the crust forming large intrusions (e.g. the Lugar Sill). This
particular intrusion is significant in that it is the type location for the rock type, lugarite. The
area is also crossed by numerous E–W-trending dykes from this period, some of which are
expressed as topographic features (e.g. between Lenzie and Torpichen).
Page 237
10 January, 2002
Zone 19 therefore provides crucial evidence for the closure of the Iapetus Ocean during the
Ordovician and Silurian periods and allows an understanding of the palaeogeographic and
palaeoenvironmental conditions during the subsequent Devonian, Carboniferous and
Permian periods. Igneous intrusions occurred in association with the closure of the Iapetus
Ocean and the subsequent crustal stretching. The diverse geological heritage encompassed
by zone 19 is reflected by the variety of GCR blocks represented (Table 19.1).
3
Palaeontology
Ordovician and Silurian sediments of the Southern Uplands contain a fossil marine fauna,
consisting largely of graptolites, which have been invaluable in understanding the geological
structure of the area. To the north of the Southern Uplands, Silurian lacustrine and lagoonal
siltstone facies of the Lesmahagow area have yielded some of the world’s oldest known
fossil fish populations, including the oldest known vertebrate, Jamoytius kerwoodi, at Birk
Knowes. Shrimps and eurypterids (water scorpions) existed alongside the fish fauna and
their fossils also occur within the rock sequences.
Lower and Upper Carboniferous sedimentary rocks occur both to the north and south of
the Southern Uplands. The northern sediments occur at the edge of the Midland Valley
basin of sedimentation, whereas the sequences in the south constitute the northern margin
of a northern English basin of sedimentation, separate from the Midland Valley. The rock
sequences in both areas provide a characteristic suite of shallow marine and estuarine fossil
faunas and floras, significant for their use in palaeogeographic and palaeoenvironmental
reconstructions.
Reptile footprints discovered in the Permian sandstones during quarrying (e.g. at
Locharbriggs quarry) reveal a fossil fauna akin to that in the Elgin area and are important in
understanding the evolutionary development of terrestrial animals. The fossil tracks of
mammal-like reptiles have also been found within the Triassic sequence of desert
sandstones near Annan.
4
Geomorphology
Glacial erosion has shaped the main valleys and moulded the western uplands, which are
extensively ice scoured, notably east of the Merrick, but the intensity of glacial erosion
decreases eastwards towards the Lowther Hills. The Lowther Hills are deeply dissected by
narrow valleys. The coastal lowlands and dales are extensively mantled in glacial deposits,
the drumlin fields of the Solway lowlands and the area around New Galloway being
particularly notable. Many of the valleys on the south side of the uplands and the area
around Stranraer contain large spreads of glaciofluvial deposits. The only reported example
of rogen moraines in Britain occurs near Carsphairn. The northern part of the zone includes
the western part of the Ayrshire lowlands, where multiple till deposits record the
interaction of ice masses from the Highlands and Southern Uplands. During the Loch
Lomond Readvance, small glaciers formed in the corries of the western hills, and fine
examples of end moraines are noted at the Tauchers and Loch Dungeon. Periglacial stone
stripes and meltwater channels are particularly well developed on Tinto Hill.
The environmental history of the zone has been investigated at a number of sites
particularly in the Galloway Hills and in the coastal lowlands. Mixed deciduous woodlands
Page 238
10 January, 2002
with oak and elm developed during the middle Holocene. Pine was present in the Galloway
hills but was never a dominant species. Blanket peat also expanded during the middle
Holocene. Human impacts are recorded from before 5000 14C yr BP, and there are
important recent records of loch acidification during the industrial period preserved in the
loch sediments.
The zone contains two starkly contrasting types of coastline. On the short, exposed
western margins, between Downan Point and Finnarts Bay, the shoreline is rocky with
occasional small bluffs and promontories. The difference between this coastline and that of
the inner Solway Firth could not be more pronounced. There, relatively sheltered
conditions prevail and wide expanses of sandflat, mudflat and saltmarsh have developed. To
the east of Rockcliff particularly, in the inner Solway Firth, vast tracts of intertidal sandflat
exist. These are separated by constantly shifting tidal channels and are considerably more
extensive than elsewhere in Scotland. The saltmarshes too are extensive, even though some
have been lost to land claim. Typically, these are developed upon low, raised beaches of
sand or shingle and display a complex micro-topography of pans, creeks and terraces.
Especially fine examples are located on the northern shores of the Solway at Caerlaverock,
where growth of a 1-km-wide swathe of marsh has been recorded in just 140 years. Raised
estuarine deposits occur extensively along the Solway coast and provide valuable records of
sea level changes during the last c.13,000 14C years. Key sites include the Cree estuary,
Priestside Flow and Crook’s Pow valley, as well as Redkirk Point and Newbie, where
intertidal peats with tree remains occur. Because of their location in an area peripheral to
the main area of isostatic uplift in the west Highlands, such sites provide sensitive indicators
of smaller changes in relative sea level.
Zone 19 is notable for its variety of river types. The majority of the main rivers in this zone
drain south, the exceptions being the headwaters of the Clyde and Doon, which drain
north, and the Water of Girvan, the headwaters of the River Stinchar and Water of Ayr,
which drain west. The upland headwater tributaries of the major rivers, the Nith, Annan,
Ken and Dee, are akin to mountain torrents, becoming wandering gravel bed rivers in the
middle reaches, and then meandering rivers further downstream. The headwaters of
streams which do not drain the high ground (e.g. the Water of Luce, River Bladnoch and
Urr Water) are mainly meandering, with dendritic tributary systems.
A feature of this zone is that many of the major rivers end in silty estuaries which feed the
Solway Firth (e.g. the Cree, Dee, Fleet, Urr and Nith). Bed material therefore fines to silt
within the system, and meandering and sinuous planforms dominate the lower courses.
Some small rivers draining towards the south coast (e.g. the Lochar Water, New Abbey
Pow, Kirkgunzoen Lane) can be classed as being stable lowland tortuously meandering
rivers. Some rivers (e.g. the Potterland Land and Beck Burn) show signs of having been
straightened in the past.
The confluence of the River Clyde and the Medwin Water in the north-eastern corner of
the zone is a fluvial geomorphology SSSI and GCR site. Here the River Clyde actively
meanders across the floodplain; large-scale active meanders that are largely undamaged by
river engineering are relatively rare in Britain. The history of floodplain activity is
exceptionally well documented in maps and air photographs over the last 150 years. The
history of channel migrations over the last c. 400 years is also contained within the alluvial
sediments on the floodplain. One bend, in the upper part of the reach, migrated around 280
m in 129 years (an average rate of change in excess of 2 m per year). The catchment of an
Page 239
10 January, 2002
upstream tributary of the Clyde, the Glengonnar Water, has been subject to historic lead
mining operations, and flood plain sediments have been found with lead concentrations in
excess of 75,000 mg kg–1.
There are a number of lochs and lochans in the zone, but few are within the major river
systems (e.g. Loch Ken within the Dee system and Loch Doon within the Doon system). It
is noteworthy that Loch Dee in the headwaters of the River Dee has been the subject of a
long-term monitoring survey into the effects of acid episodes on water chemistry.
5
Soils
Soils in this zone are formed on a wide range of drift sediments, resulting in a wide variety
of soil types. Brown earths constitute nearly a quarter of all soils in the zone, occurring
where the drift has relatively high nutrient status and where topography and climate are not
limiting (e.g. in the Minnoch valley). Brown earths can be valuable agricultural soils and most
have been extensively modified by agricultural activities over a long period of time. Only
0.3% of South West Scotland as a whole has high (grade 2) agricultural land as high rainfall
limits crops yields, except for the area around Ayr, which could have been potentially grade
1 land had it not been developed. In areas where drainage and topography are limiting, peats
and podzols are extensively developed, together comprising c. 42% of the soils of the zone.
Where these soils are unmodified, they support distinctive vegetation such as blanket-bog
communities and acid bent-fescue grassland. Blanket peat is common on the foothills of
South Ayrshire and Wigtownshire and in the ice-scoured basins of Glen Luce. On the
granite hills of Galloway, podzols occur in association with rankers and some blanket peat.
In places, sequences of brown earths and podzols occur together such as on the slopes of
the Lowther Hills. The extensive peaty soils are of considerable significance and include the
internationally important Silver Flowe bog. In the coastal zone, remnants of formerly more
extensive lowland peatbogs are developed on raised estuarine sediments. These include the
nationally important Lochar Moss and Moss of Cree.
6
Summary of key Earth science features in the Western
Southern Uplands and Inner Solway
The principal Earth heritage interests in the Western Southern Uplands and Inner Solway
are summarised in Table 19.1. The zone contains a total of 43 GCR sites.
Page 240
10 January, 2002
Table 19.1 GCR sites in Western Southern Uplands and Inner Solway
GCR block
No. of sites
Principal interests
Caledonian Igneous
4
Permo-Carboniferous Igneous
5
Arenig–Llanvirn
1
Wenlock
1
Westphalian
3
Permo-Trias
2
Dinantian
3
Arthropoda
Palaeozoic Palaeobotany
Vertebrate Palaeontology
Mineralogy
Quaternary of Scotland
2
1
4
6
8
Fluvial Geomorphology
1
Saltmarsh Geomorphology
1
Granite intrusions associated with the closure of
Iapetus Ocean
Type locality for lugarite and classic example of
magmatic differentiation
Odovician palaeogeography and palaeoenvironment
reconstruction
Silurian palaeogeography and palaeoenvironment
reconstruction
Late Carboniferous palaeogeography/environmental
reconstruction
Permo-Trias palaeogeography/environmental
reconstruction
Early Carboniferous palaeogeography/environmental
reconstruction
Internationally significant arthropod fauna
Carboniferous flora
Internationally significant fish fauna
Intrusion and fracture associated mineralisation
Representative sites for glacial landforms and glacial
history, palaeoenvironmental changes and sea level
changes
Lowland river meanders and history of floodplain
development
Saltmarsh and mudflat development
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in Western Southern Uplands and Inner Solway are summarised in Table 19.2.
However, there is no systematic information on current impacts or trends.
Page 241
10 January, 2002
Table 19.2 Potential pressures and vulnerability of Earth heritage interests in the Western Southern
Uplands and Inner Solway
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral
extraction, infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; river management
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Vulnerable to drainage of bogs and peat extraction
Vulnerable to river engineering and management;
afforestation gravel extraction; land management changes
Vulnerable to land claim, coast protection and sea level rise
Vulnerable to land claim, coast protection
Vulnerable to land management changes, pollution
Palaeontological interests
Quaternary depositional landforms
and exposures
Records of sea level change
Palaeoenvironmental records
Fluvial geomorphology
Saltmarshes
Estuarine geomorphology
Soils
8
•
•
•
•
•
•
•
•
•
•
•
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
Irresponsible fossil collecting has resulted in some loss of the palaeontological resource
in the Lesmahagow area.
There is some suggestion among local landowners that afforestation in the headwaters
of the River Nith has affected the hydrology (magnitude and flashiness of peak flows) of
the main river.
Research at Loch Dee shows that the water chemistry of some rivers in this zone is
susceptible to acidification through afforestation and scavenging of pollutants from the
atmosphere.
Open cast mining has had some impact on the headwaters of the Nith, causing it to be
diverted.
Coast defences have obscured key exposures at Redkirk Point.
There has been some deterioration in the condition of the exposure at Nith Bridge
following river bank protection works. However, this has been mitigated by the design
of the scheme.
Coastal erosion at Newbie has led to some natural loss of sediments, but has exposed
new interests on the foreshore (Cressey, 1999).
Dumping of rubble as coast protection has obscured some sections at Newbie.
Dumping of rubble as bank protection has interfered with the natural evolution of the
River Clyde meanders.
The River Clyde meanders have been modified by channel dredging under the Land
Drainage Scheme (this has not affected the planform but has probably reduced the rate
of channel change).
Page 242
10 January, 2002
9
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1996) Coasts And
Seas Of The United Kingdom. Region 13. Northern Irish Sea: Colwyn Bay to Stranraer including the Isle of
Man. Joint Nature Conservation Committee, Peterborough
Bown, C.J., Shipley, B.M. and Bibby, J.S. (1982) Soil and Land Capability for Agriculture. South-West Scotland.
Aberdeen, The Macaulay Institute for Soil Research.
Brazier, V., Kirkbride, M. P. And Werritty, A. (1993) Scottish landform examples: the Clyde-Medwin
meanders. Scottish Geographical Magazine, 109, 45–49.
Cameron, I.B. and Stephenson, D, 1985. British Regional Geology: the Midland Valley of Scotland (third
edition). British Geological Survey (HMSO, London).
Cleal, C.J. and Thomas, B.A. (1995) Palaeozoic Palaeobotany of Great Britain. Geological Conservation
Review Series No. 9. Joint Nature Conservation Committee, Peterborough.
Cleal, C.J. and Thomas, B.A. (1996) British Upper Carboniferous Stratigraphy. Geological Conservation
Review Series No.11. Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Cressey, M. (1999) Solway Firth environmental assessment and coastal management survey (Newbie
Cottages to Broom Knowes, Near Powfoot). Scottish Natural Heritage Commissioned Report
F99/AC114 (Unpublished report).
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. GCR Series No. 16. Joint Nature
Conservation Committee, Peterborough.
Firth, C.R., Collins, P.E.F. and Smith, D.E. (1999) Coastal Processes and Management of Scottish Estuaries. V.
The Solway Firth. Scottish Natural Heritage Review No. 128.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage Commissioned
Report F98AC112 (Unpublished report).
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Gregory, K. J. (1997) The Fluvial Geomorphology of Great Britain. Geological Conservation Review Series
13. Chapman and Hall, London.
Greig, D.C. (1971) British Regional Geology: the South of Scotland (third edition). British Geological Survey
(HMSO, London).
HR Wallingford, 2000. Coastal Cells in Scotland. Cell 7 – The Solway Firth. Report to Scottish Natural
Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and Historic Scotland. SNH
RSM Report No. 149. Battleby.
Marshall, J.R. (1962) The Morphology of the Upper Solway Saltmarshes. Scottish Geographical Magazine,
78, 81–99.
Mather, A.S. (1979) Beaches of South-west Scotland Volume II. Dept. of Geography, University of
Aberdeen. Countryside Commission for Scotland. Perth.
May, V. and Hansom, J.D. in press. Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Rafaelli, D. (1992) Conservation of Scottish Estuaries. Proceedings of the Royal Society of Edinburgh, 100B,
55–76.
Rowan, J.S., Barnes, S.J.A., Hetherington, S.L., Lambers, B. and Parsons, F. (1995) Geomorphology and
pollution: the environmental impacts of lead mining, Leadhills, Scotland. Journal of Geochemical
Exploration, 52, 57–65.
Ross, G. (1927) The superficial deposits in the Clyde Valley at Bonnington, 1_ miles south of Lanark.
Geological Survey of Great Britain. Summary of Progress of the Geological Survey of Great Britain and the
Museum of Geology for the year 1926, HMSO, London, 158–160.
Rowan, J. S., Black, S. And Schell, c. (1999) Floodplain evolution and sediment provenance reconstructed
from channel fill sequences: The Upper Clyde Basin, Scotland. In Brown, A. G. and Quine, T. A. (Eds)
Fluvial Processes and Environmental Change. John Wiley and Sons Ltd, Chichester, 223–240.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Page 243
10 January, 2002
Stephenson, D., Bevins, R.E., Millward, D. Highton, A.J., Parson, I., Stone, P. and Wadsworth, W.J. (1999)
Caledonian Igneous Rocks of Great Britain. Geological Conservation Review Series No. 17. Joint Nature
Conservation Committee, Peterborough.
Stone, P. (1996) Geology in south-west Scotland – An Excursion guide. Nottingham, British Geological
Survey.
Tipping, R.M. (1997) Vegetational history of southern Scotland. Botanical Journal of Scotland, 49, 151–162.
Tipping, R.M. (1999) The Quaternary of Dumfries and Galloway. Field Guide. London, Quaternary Research
Association.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 3,4,5,6,7,8,9,10,14,15,16,23
Soil Survey of Scotland Maps: 1:250,000 sheets 6 and 7 encompass Zone 19 and coloured 1:63,360
sheets 8 and 4 cover the western part only of this zone. MLURI, Aberdeen
Page 244
10 January, 2002
ZONE 20
1
•
•
•
•
•
•
•
•
•
•
•
2
BORDER HILLS
Highlights
The international Ordovician–Silurian boundary stratotype at Dob’s Linn.
Sections through the Southern Uplands accretionary wedge.
The Southern Upland Fault.
Important Silurian arthropod fauna.
Devonian sedimentary basins founded on the Southern Uplands accretionary wedge.
Devonian and Carboniferous volcanic sequences.
Glencartholm: one of the most important Palaeozoic fossil fish sites in the world.
Glacial deposits representative of the Loch Lomond Readvance in the Southern Uplands.
Excellent examples of glacial meltwater channel systems.
Records of Late-glacial palaeoenvironmental change.
Good example of misfit streams and the spectacular Grey Mare’s Tail waterfall.
Geology
The Southern Uplands, which extend into the neighbouring Zones 18 and 19, represent a
large portion of the Border Hills zone. Rocks that were once sands and muds on the floor
of the Iapetus Ocean form the geological framework beneath the rather gentle rolling
upland landscape. Deposited over a 70-million-year period, between 490 million and 420
million years ago, during the Ordovician and Silurian geological periods, these rocks bear
testimony to the closure of the ocean with the coming together of what is now the North
American continent and Northern Europe, with the joining of the crustal foundations of
both Scotland and England.
Two major junctions within Scotland’s crustal foundations occur within the zone and are
intimately associated with the closure of the Iapetus Ocean. In the south, along a NE–SW
line that follows the line of the Solway and the Scotland–England border, there is the
‘Iapetus Suture’, which marks the generally recognised zone of closure of the ancient ocean.
At the north of the zone, running in a similar NE–SW line along roughly the same route as
the A702, there is the Southern Uplands Fault, which marks the northern limit of the
Southern Uplands and its junction with the Midland Valley.
The ancient sands and muds of the Southern Uplands can be grouped in terms of age into
two major NE–SW-running units. The older Ordovician rock layer sequences occur in the
north, at the Southern Upland Fault; the younger Silurian sequences, making up the bulk of
the Southern Uplands, occur to the south. Within these two major subdivisions there are
several further subdivisions and much evidence of rock layer folding and faulting. By using
fossils known as graptolites, a now extinct group of colonial plankton organisms, and
through the application of plate tectonic theory, the structure and origin of the Southern
Uplands has largely been determined. A very elegant model now explains how the muds
(black shales) and sands (greywackes) of the Southern Uplands represent marine sediments
that were scraped off the floor of Iapetus to form a wedge-shaped package (accretionary
wedge) that was heaped onto the northern continent as the continents carrying England and
Scotland collided and the ocean between them closed. This collision also affected much of
what was to become Scotland and is known as the Caledonian Orogeny or mountain-building
event. Although folded and faulted, the Southern Uplands contain the internationally agreed
boundary stratotype between the Ordovician to Silurian geological periods at Dob’s Linn.
Page 245
10 January, 2002
Below the accretionary wedge, the ocean floor of Iapetus sank beneath the southernmost
margin of the continental landmass to the north, which in a general sense corresponds
today to the Southern Highlands and the Midland Valley. This process of ‘subduction’ led to
the formation of a chain of volcanoes that are thought to have lain to the north in a NE–SW
line along what is now the Midland Valley. Volcanic clasts within the sediments of the
Southern Uplands are indicative of this activity and of the oceanic crust being consumed
beneath the ‘Scottish’ continent. However, tangible evidence for the volcanic chain is now
buried beneath younger rocks.
As the ocean finally closed along the line of the Solway, between about 420 million and 400
million years ago, the chain of volcanoes in the Midland Valley ceased eruption and the
entire area subsided after relaxation of the general north–south compression forces that
closed the ocean. Downward movement of the crust to the north the Southern Uplands
Fault, which originally represented the northern margin of the accretionary wedge and its
contact with the northern continent, together with corresponding movement along the
Highland Boundary Fault to the north, led to the formation of the Midland Valley.
Deposits of Silurian sands, muds and silts in the vicinity of the Pentland Hills represent one
of a series of ‘inliers’ that occur along the southern margin of the Midland Valley.
Surrounded by younger Carboniferous sedimentary rocks, these older sediments were
deposited in shallow marine lagoons that were the last vestiges of the Iapetus Ocean that
occurred between the massive accretionary wedge that had built up to the south and the
dying volcanic chain to the north.
Devonian, or Old Red Sandstone, sediments in the Midland Valley in the north of the zone,
in the Dolphinton–Pentlands area, represent terrestrial environmental conditions that
prevailed over the area, between 400 million and 360 million years ago after the closure of
Iapetus. Ephemeral rivers flowed northwards through what would have been an arid desert
landscape carrying sediment from the Southern Uplands into the newly formed Midland
Valley Basin. Relatively small depressions within the mountainous landscape of the Southern
Uplands also received sediment during Devonian times, forming small sedimentary basins
such as that in the vicinity of Lauder. Palmers Hill Railway cutting, south of Hawick, provides
exposures through Upper Devonian sediments and includes ancient soil profiles.
Crustal instability during the Devonian period gave rise to volcanism within the zone and
elsewhere across the country. The Pentland Hills are in part composed of lavas produced
during this time as are the Cheviot Hills at the eastern extremity of the site.
Lower Carboniferous sedimentary rocks occur in the north and south of the zone on either
side of the Southern Uplands. As in the present day, the uplands at that time separated
areas of low-lying ground. In the Midland Valley a multiplicity of alternating shallow marine
and low-lying terrestrial environments dominated the landscape, as sea levels fluctuated and
the valley continued to subside. This resulted in a variety of sediments being laid down,
including, sandstone, siltstones, shales, mudstones, limestones and the occasional coal. A
very similar picture occurred to the south across the accretionary wedge, where the
Carboniferous rocks of the Borders form the marginal deposits of the large
Solway–Northumbrian Basin. Penton Linns east of Canonbie, illustrates an excellent Lower
Carboniferous sedimentary sequence. To the north-east of Penton Linns, exposures of
volcanic rocks including lavas, are testimony to volcanism indicative of crustal instability
during the Lower Carboniferous.
Page 246
10 January, 2002
The most recently formed rocks in the zone are 60-million-year-old igneous intrusions that
occur in the form of dykes. These basic rocks were emplaced into long linear NW–SE
trending cracks as the crust beneath the zone was stretched during an event that led
ultimately to the split in the continent between Scotland and North America with the
formation of the Atlantic. The largest dykes are in the order of 10–15 m wide and can be
traced to the Isle of Mull, a major centre of volcanic activity during the Tertiary Period.
3
Palaeontology
Ordovician and Silurian sediments of the accretionary prism forming the Southern Uplands
contain a fossil marine fauna, consisting largely of graptolites that have been invaluable in
understanding the geological structure of the area. In addition, graptolites found within the
rock sequences at Dob’s Linn form the basis for the International Boundary Stratotype
between the Ordovician and Silurian geological periods.
Marine deposits within Silurian inliers at the southern margin of the Midland Valley, such as
that at North Esk, yield fossils of shallow marine faunas that include eurypterid water
scorpions, brachiopods and trilobites.
On the fringes of the zone, around the Silurian inliers, Carboniferous rocks yield a range of
fossil material, representing a multiplicity of ecosystems that flourished in shallow marine,
brackish lagoon, deltaic, lacustrine and coal swamp environments. Of the Borders
Carboniferous sites, Glencartholm is perhaps the most famous. To date, Glencartholm has
yielded a fish fauna comprising 35 species, 20 of which are unique to the site. Consequently
it is regarded as one of the most important fish sites in the world. Over 25 species of the
original Carboniferous floral assemblage and an equally diverse arthropod fauna, also found
at Glencartholm, make it an invaluable site for understanding Carboniferous biotas.
4
Geomorphology
The eastern parts of the Southern Uplands have generally been little modified by glacial
erosion and show similar features to the hills of the Grampian fringe. They are commonly
dissected by relatively steep and narrow valleys and the slopes are extensively mantled in
soliflucted debris. In the central and western parts, glacial erosion has been more effective in
shaping valleys and corries and in scouring the hillsides, notably in the Loch Skeen area.
Here there is the striking, fault-guided trough now occupied by the Moffat water. Glacial
deposits and soliflucted debris infill many of the valleys, often forming benches where later
stream erosion has dissected the infill. As the last ice sheet wasted, meltwater channels
developed in a number of areas, with particularly fine examples on the northern flanks of
the Lammermuir Hills and Moorfoot Hills. During the Loch Lomond Readvance, small
glaciers formed in the White Coombe hills, and their hummocky deposits are evident
around Loch Skeen and in the Talla valley. A sequence of deposits at Bigholm Burn provides
an important record of Late-glacial environmental history, notable for the presence of
beetle faunas.
This zone is dominated by the catchment of the River Tweed and its tributaries. In addition,
however, the zone contains the headwaters of some rivers draining north to the Firth of
Forth (North and South Esks, Water of Leith and Tyne Water), draining south towards the
Solway Firth (River Esk, Moffat, Dryfe and Liddle Waters) and also contains tributaries of
Page 247
10 January, 2002
the River Clyde. Despite the diversity in drainage direction, some fluvial features (such as
meandering and the presence of misfit streams in over-widened valleys) can be identified
across the entire zone. The zone also contains a number of water supply reservoirs (e.g.
Talla, Megget and Fruid).
The Leader, Gala and Whiteadder Waters drain the southern side of the Lammermuir Hills,
and thus the upper parts within the zone are mainly steep, active, boulder bed tributaries.
This contrasts with the Heriot Water, an upstream tributary of the Gala Water, which is a
misfit stream meandering in an over-widened valley.
The Etterick, Yarrow and Ale Waters flow eastwards towards the Tweed. They have
dendritic tributary systems and wandering gravel bed upper and middle reaches. Meandering
on their main stems is restricted by their variable floodplain width (the Etterick and the Ale
meander tortuously in parts, whereas the Yarrow floodplain is generally narrow, which
restricts meandering). The headwaters of the Teviot, the Jed and Bowmont Waters and the
College Burn drain the Cheviot Hills and have a number of steep, short upland tributaries,
more akin to the mountain torrents of northern Scotland. Across the zone, the upper and
middle reaches tend to be dynamic wandering gravel bed rivers, showing limited division and
occasionally retaining former channels on the floodplain (e.g. on the Teviot). Meandering
becomes increasingly persistent downstream. The Tweed wanders in its upper reaches, with
first- or second-order tributaries, and becomes increasingly meandering downstream,
flowing within a wide meander train in its middle reaches. Moving downstream, the
meanders become increasingly tortuous downstream with some rectangular bends.
The south-flowing Esk and Liddle Water meander within wide valleys in their upper and
middle reaches. The Esk becomes increasingly sinuous downstream as a result of increased
constraint and reduced valley width. The tributaries of the Esk and Liddle are themselves
meandering, and often have dendritic, well-developed networks. The Grey Mare’s Tail is a
spectacular waterfall on a tributary of the Moffat Water, which flows into the Annan (mainly
within Zone 19).
5
Soils
The soils in the Southern Uplands are dominated by peaty podzols and brown forest soils.
Over a third of soils are brown earths and therefore agriculturally valuable and have been
extensively amended by cultivation. Peat has developed on some gentle slopes (10% of the
total soils resource) stimulated by a high degree of soil wetness. Soils of national significance
include montane soils on hill tops such as Broad Law as they are relatively rare in this part
of Scotland. Soils of local significance are those developed on glaciofluvial sands and gravels
that are prone to disturbance by gravel extraction.
6
Summary of key Earth science features in the Border Hills
The principal Earth heritage interests of the Border Hills are summarised in Table 20.1. The
Border Hills includes a total of 25 GCR sites.
Page 248
10 January, 2002
Table 20.1 GCR sites in the Border Hills
GCR block
No. of sites
Principal interests
Caledonian Structures
Wenlock
Caradoc–Ashgill
Llandovery
Dinantian
1
1
1
3
3
ORS Igneous
Non-marine Devonian
Permo-Carboniferous Igneous
Westphalian
1
1
3
1
Permian–Carboniferous
Fish/Amphibia
Palaeobotany
Arthropods
Quaternary of Scotland
1
Structures formed during the Caledonian Orogeny
Representative Middle Silurian rock sequences
Representative Upper Ordovician rock sequences
Representative Lower Silurian rock sequences
Representative Lower Carboniferous rock
sequences
Igneous rocks formed during Devonian times
Devonian terrestrial sediments
Igneous rocks formed during Carboniferous times
Representative Upper Carboniferous rock
sequences
Carboniferous age fossil fish
1
2
4
Fluvial Geomorphology
1
7
Carboniferous age fossil plants
Fossil remains of Silurian eurypterids
Classic examples of glacial meltwater channels;
Loch Lomond Readvance glacial landforms; records
of Late- glacial and Holocenepalaeoenvironmental
changes
Waterfall associated with differential glacial
erosion
Pressures and trends
The potential pressures on different components of the Earth heritage and their
vulnerability in the Border Hills are summarised in Table 20.2. However, there is no
systematic information on current impacts or trends.
Table 20.2 Potential pressures and vulnerability of Earth heritage interests in the Border Hills
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; river management
Vulnerable to drainage of bogs and peat extraction
Vulnerable to river engineering and management;
afforestation; land management changes
Vulnerable to land management changes, pollution, peat
erosion
Palaeontological interests
Quaternary depositional landforms
and exposures
Palaeoenvironmental records
Fluvial geomorphology
Soils
Page 249
10 January, 2002
8
•
•
9
State of the resource
Information on individual GCR sites is available from the Earth Science Site
Documentation Reports.
The Glencartholm fossils beds were quarried for fossils in the 1990s.
Bibliography
Cleal, C.J. and Thomas, B.A. (1995) Palaeozoic Palaeobotany of Great Britain. Geological Conservation
Review Series No. 9. Joint Nature Conservation Committee, Peterborough.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Creig, D.C. (1971) British Regional Geology: The South of Scotland (third edition). British Geological Survey
(HMSO, London).
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. GCR Series No. 16. Joint Nature
Conservation Committee, Peterborough.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage Commissioned
Report F98AC112
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review Series
No. 6. Chapman and Hall, London.
Gregory, K.J. (1997) Fluvial Geomorphology of Great Britain. Geological Conservation Review Series, No.
13. Chapman and Hall, London.
Rushton, A.W.A., Owen, A.W., Owens, R.M. and Prigmore, J.K. (1999) British Cambrian to Ordovician
Stratigraphy. Geological Conservation Review Series No. 18. Joint Nature Conservation Committee,
Peterborough.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Tipping, R.M. (1997) Vegetational history of southern Scotland. Botanical Journal of Scotland, 49, 151–162.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 10, 11, 16, 17, 24, 25, 33.
Soil Survey of Scotland Maps: 1:250,000 sheet 7 encompasses Zone 20; coloured 1;63,360 sheets 17, 24
and 25 cover some of the zone and uncoloured 1:50,000 sheets 78, 79 and 85 cover the central parts
of the Border Hills. MLURI, Aberdeen.
Page 250
10 January, 2002
ZONE 21
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
MORAY FIRTH
Highlights
Southern margin of the Orcadian Basin.
Orcadian Basin lake fossil fauna.
Onshore extension of Permian, Triassic and Jurassic North Sea Basin sequences.
Permian–Triassic ‘mega-fauna’ body fossils and traces.
Preservation of key sequences of Quaternary deposits, including rare interglacial and
interstadial deposits.
Crucial geomorphological and sedimentary evidence for the pattern of deglaciation of
the last ice sheet.
Some of the best examples of eskers and kame terraces in Britain.
Geomorphological and stratigraphic records of Lateglacial and Holocene sea level
changes.
The diversity of coastal landforms and processes, relative to other zones.
Excellent example of coastal erosion and weathering in sandstone.
The exceptional size and diversity of the beach/dune systems including, at Culbin, some
of the highest dunes in the country and, both there and at Morrich More, rare parabolic
dunes.
Excellent examples of shingle spits, encompassing the most clearly developed and most
active spits in Scotland.
Excellent example of a rapidly accreting coastal foreland.
A diverse range of saltmarsh settings, including the best developed back-barrier
saltmarshes in Scotland.
Estuarine geomorphology, including one of the few completely natural estuaries in the
United Kingdom (the Dornoch Firth) and which, moreover, provides an extremely
important and rare example of estuarine dynamics in an area of falling relative sea level.
The exceptional, braided, gravel bed river system of the Lower River Spey and its
palaeochannels.
Geology
Of all the zones, the boundaries of the Moray Firth Zone correspond most closely to actual
geological boundaries, following the junction between ancient metamorphic and younger
sedimentary rocks. For the last 400 million years the zone has represented the margin of a
low-lying area of the Earth’s crust which now corresponds to the Moray Firth and North
Sea. Spanning around 1500 million years of Earth history, the geology of this zone is one of
the most diverse of the 21 zones.
Rocks belonging to the Moine Assemblage are the oldest rocks in the zone. Outcropping
around the western and southern margins of the zone, these metamorphic rocks form the
foundation of the zone and underlie the younger sedimentary rocks around the coastal strip.
Now occurring as schists and gneisses, the Moine Assemblage was once a huge pile of
sediment that accumulated over several hundred million years between 1500–1050 million
years ago at the southern edge of a continent. Referred to as Laurentia, this ancient
continent encompassed what is now North America, Greenland and Northwest Scotland
and was made up of Lewisian Gneiss. On this continental margin, large quantities of sand
and other sediment, derived from erosion of the gneisses, accumulated, eventually giving
rise to the Moine. Named after the peninsula of a’Mhoine in northern Sutherland, the Moine
Page 251
10 January, 2002
Assemblage is composed of three distinct Divisions: the Morar Division, the Glenfinnan
Division and the Loch Eil Division. The precise relationship between the three divisions is
still being debated, but the Morar and Loch Eil Divisions are regarded as the oldest and the
youngest respectively. Within the zone, Moine outcrops in the south-east of the zone in the
vicinity of Loch Ness represent portions of the Loch Eil Division. Small outcrops of the
Glenfinnan Division occur along the north-east coast of the Black Isle and at Cromarty.
After the deposition of the sediment pile, the collision of continental landmasses, through
the mechanism of plate tectonics, deformed and metmorphosed the sediments. The
metamorphic and deformational history of the Moine Assemblage was complex and there
were several phases of mountain building, or orogeny, resulting from continental collision,
starting around 1000 million years ago. The various sedimentary rocks were
metamorphosed to schists and gneisses, with the recrystalisation of sandstones to quartzites
and the more muddy sediments to pelites. The metamorphism was not entirely uniform,
with the result that some portions of the assemblage were subjected to high-grade
metamorphism, resulting in the formation of gneisses, whereas other areas escaped
relatively unscathed with the preservation of the features characteristic of the original
sedimentary rock, such as layering.
The most recent phase of metamorphism and deformation occurred during the Caledonian
Orogeny between 400 million and 500 million years ago. This orogenic event folded and
metamorphosed the previously deformed metamorphic Moine rock, and toward the end of
the event, the Great Glen Fault was formed. This major fault in Scotland’s crust, which
bisects the zone, cuts through the Moine sequence and represents the point where the two
blocks of crust, which form Scotland’s foundations, slid past one another. The lateral
displacement of the crust on either side of the fault is major and amounts to many tens of
kilometres, but the fault is no longer interpreted as a terrane boundary, like the Iapetus
Suture, that represents the ‘join’ in the crust between Scotland and England, which is
described in Zone 20. The fault has been reactivated during subsequent periods of Earth
movements and is still active today. South of the Great Glen Fault, components the Moine
Assemblage are thought to represent the base of the Dalradian Supergroup, another major
sequence of sediments deposited on the margin of the Laurentian continent between 700
and 500 million years ago and which underlies much of Zones 9–15. The Dalradian was
deformed and metamorphosed during the Caledonian Orogeny and a portion of it,
corresponding to the Grampian Group, underlies the eastern tip of the zone.
Within the zone, a granite intrusion occurs at the north-western tip of Loch Ness. Called
the Abriachan Granite, this mass was intruded into the Moine as a consequence of the
metamorphism and deformation of the Moine Assemblage. The granite was derived from
the actual partial melting of rocks lower within the crust as the deformation and
metamorphism of the Moine took place. The melting resulted in the formation of great
masses of silica-rich melt that moved upward through the crust and which became emplaced
within the deformed and metamorphosed Moine rocks.
Resting upon Moine rock and underlying most of the zone, sedimentary rocks were
deposited during the Devonian, Permian, Triassic and Jurassic periods, between 400 million
and 145 million years ago. At the start of the Devonian period, the Caledonide Orogeny had
all but ended, and the resulting mountain chain was gradually eroded over millions of years,
producing sand, silt, mud and other sediment that accumulated in the basins and hollows
within and away from the high ground. Crustal tensions at this time, rather than pushing the
Page 252
10 January, 2002
crust together were instead pulling it apart, leading to subsidence to the east of the zone in
what is now the Moray Firth and the North Sea. This led to a major sedimentary basin
developing with time in the North Sea area. NE–SW-trending faults, such as the Helmsdale
Fault just outwith the zone to the east, represent the boundary edge of the subsiding
sedimentary basin.
The first Devonian (or Old Red Sandstone) deposits were laid down during the Lower part
of this period, and in the vicinity of Beauly can be seen to rest with an unconformable
contact upon the Moine metamorphic rocks. Consisting of conglomerates, grits, coarse
sands, silts and mudstones, these deposits would have been deposited by river systems that
flowed, in a hot arid climate, from the high mountainous ground across alluvial fans towards
the subsiding areas in the east. Sediment deposition continued into Middle Devonian times,
with sediment accumulating in the area that is now the Black Isle and along the line of the
Great Glen Fault. In the area that is now the Moray Firth, a vast alluvial plain developed
outwards from the Highlands, with the deposition of a range of sediment types from course
breccias and conglomerates near the source in the Highlands and at the boundary faults, to
fine sands and silts out on the plain. Out in the basin, a large freshwater lake occupied the
area that now corresponds to Orkney and north-eastern Caithness. Known as the Orcadian
Basin Lake, this body of fresh water fluctuated greatly during the Middle Devonian
depending on climatic and other environmental conditions. At times of expansion, the lake’s
waters lapped around the eastern edge of the zone, leading to the deposition of finergrained lake margin sediment, rather than the normal coarse fluvial deposits. Within these
deposits, evident in the sequences at Tynet Burn and Dipple Brae, the fossil remains of a
rich and diverse fish fauna are to be found. By Upper Devonian times, approaching 360
million years ago, the basin lake had silted up and fluvial conditions prevailed across the
Moray Firth Basin. Fish and early amphibians inhabited the fluvial systems that ran north and
north-eastwards through the zone. The prevailing winds at the time swept unconsolidated
sand into dunes that are evident in the sequences at Tarbat Ness.
Scotland drifted northwards across the equator during the Carboniferous Period but there
are no deposits that bear witness to the tropical environmental conditions that would have
persisted throughout the zone over that 60-million-year period. By Permian and Triassic
times, the Moray Firth and North Sea area continued to subside, and sediment once again
accumulated in the basin, being deposited directly upon the Devonian deposits. Rocks of this
age around Elgin and Lossiemouth, such as occur at Clashach Quarry and Masonhaugh, are
dominated by ‘fossil’ sand dunes, indicating a return to warm and arid environmental
conditions. The fossil remains and traces of animals that lived in this arid environment are
preserved in the Permian and Triassic sequences.
At the start of the Jurassic period, rising sea levels led to widespread flooding of the Moray
Firth and North Sea area, which continued to subside as sediment derived from the
surrounding high ground accumulated. North of Elgin the occurrence of Jurassic rocks has
been proved from boreholes. Dating back to the Lower Jurassic, around 195 million years
ago, these Lower Jurassic sandstones, siltstone, mudstones and marls (lime-muds) represent
deposition in a coastal lagoonal setting. Upper Jurassic mudstones, shales and oil-shales at
Ethie on the Black Isle, and to the south of Balintore, date from around 145 million years
ago and represent deeper marine conditions. Although they were deposited in a relatively
marginal position within the ancient marine environment, and are of tiny outcrop, these
Jurassic rocks are of significant economic importance for allowing an understanding of the
Jurassic and petroleum geology of the Moray Firth–North Sea Basin.
Page 253
10 January, 2002
3
Palaeontology
This zone is of national and international importance for Devonian fish and amphibians,
Permian and Triassic reptile-like animals and Jurassic marine faunas.
The Devonian sedimentary rocks along the fringes of the southern Moray Firth represent
the marginal deposits of the Orcadian Basin that extended from this zone north-eastwards
across what is now Caithness and Orkney. Although predominantly fluvial in character, with
numerous alluvial fan deposits, the Devonian sequence contains occasional deep-water
facies, ‘fish beds’, that may be correlated with those further north. These beds have yielded
the remains of a rich and diverse fish fauna that lived and died within the Devonian
lacustrine–fluvial environment. Primitive armoured fish, the lungfish forerunners of
amphibians and reptiles, and the ancestors of today’s bony fish are all represented.
Population studies of the fish beds have suggested that some of the fish species lived entirely
within the ancient basin environment, whereas others migrated from a southern ocean via
an ancient river system. Fish remains, found in fluvial portions of the sequences around the
Moray Firth, provide evidence of widespread niche utilisation and migratory habits. Deposits
of fossil plant material found in association with the fish faunas provide evidence of the basin
flora surrounding the lakes and rivers.
The Upper Devonian rocks at Scaat Craig and Tarbat Ness are of international significance
for yielding the fossil remains and traces of some of the oldest known amphibians.
Amphibian bones have only recently been discovered among the fish fossils at Scaat Craig
near Elgin; much research is still required but the bone fragments are turning out to be the
oldest amphibian remains in the UK and are among the oldest known in the world. The
fossil track-way at Tarbat Ness is one of only a handful of such early amphibian trace fossils
in the world and will provide information on the body plan of these ancient creatures. Both
sites are vital in evolutionary studies.
The tiny exposures of Permian and Triassic rocks in the vicinity of Elgin have yielded an
internationally significant fossil ‘megafauna’, representing mammal-like reptiles and early
dinosaur-like creatures. The fossils have been discovered largely through quarrying for
dimension stone at famous sites such as Cutties Hillock, Findrassie and Spynie. This fauna
inhabited an arid landscape and their tracks and traces are evident within the desertdeposited sediments. Although body fossils and traces are evidence of this late Permian and
Triassic megafauna, little is known of the flora that sustained these animals. Marine fossils
within the Jurassic rocks of the zone are testimony to the submergence of the Moray Firth
area late in Triassic/Jurassic times.
4
Geomorphology
This zone includes the coastal lowlands of the Moray Firth and Easter Ross. It was glaciated
during the Pleistocene by one of the major ice streams flowing out from the Highlands,
receiving ice from the mountains both to the north and to the south of the Great Glen. The
pattern of striations indicates that the ice generally moved towards the north-east during
the later phases of glaciation and was channelled into the inner Moray Firth, beyond which it
diverged and flowed back on to the land in both Caithness (Zone 2) and in Buchan (Zone 9).
In the eastern part of the area, a major ice stream also flowed down Strathspey. Glacial
deposits and meltwater channels are widespread. Till sheets occur extensively in the coastal
plain east of Elgin. Because the movement of the ice was onshore at times from the Moray
Page 254
10 January, 2002
Firth, erratics include materials derived from the seafloor. Because the intensity of glacial
erosion has been low, deposits pre-dating the last ice sheet are locally preserved; most
notable are those at Clava and Teindland. Glaciofluvial deposits associated with the melting
of the last ice sheet are particularly well developed in this zone, for example east of
Inverness (Strath Nairn and Kildrummie Kames), SW of Inverness (Torvean) and near
Dornoch (Dornoch Esker). The most striking landforms in the area relate to this period of
deglaciation. Particularly notable are the deposits at Ardersier and the sequence of
glaciofluvial sediments that extends from Torvean at the mouth of the Great Glen at
Inverness, through Littlemill to Kildrummie. The esker and kame terraces at Torvean are
outstanding landforms, among the largest examples of their type of Scotland, whereas the
Flemington Esker at Kildrummie is one of the longest continuous such features in Scotland.
Possible stillstands or readvances of the ice have been recognised at Elgin (Elgin Oscillation)
and Ardersier.
Around the coasts, the progressive ice wastage resulted in the formation of a series of
raised shorelines (e.g. at Ardersier and Munlochy Valley). These are isostatically tilted
towards the north-east, each successively younger shoreline extending farther west and
having a lower gradient than its predecessor. At the time of deglaciation, and continuing into
the Lateglacial Interstadial, fossiliferous marine sediments were laid down in the firths.
Considerable work has been carried out on the evolution of the coastline. In the inner
firths, records from sites such as Barnyards show that during the early Holocene the sea
level initially fell, reaching a low some time after 9000 BP, then subsequently rose during the
Main Postglacial Transgression to culminate, between 7100 BP and 5800 BP, in the
formation of the Main Postglacial Shoreline. The subsequent fall in sea level to its present
level is not securely dated, but several distinct shorelines were formed during this period, as
is illustrated by the sequence of estuarine flats at Munlochy Valley. Elsewhere in the area,
Holocene raised shoreline features are well developed and include shingle ridges (Dornoch
Firth, Tarbat Ness, Spey Bay and Culbin) and sand beach ridges (Morrich More).
There have been relatively few studies of the vegetation history of the zone. During the
middle Holocene, birch–hazel–oak woodland was predominant in the coastal lowlands, with
pine–birch towards the western margins of the zone.
The coastal zone was largely dominated by glacial deposition that has provided an ample
sediment supply for the development of extensive areas of raised beach, sand dune and
shingle beach development, as at Culbin and Spey Bay. Intervening areas of coastline show
well-developed cliffs and shore platforms developed in a variety of rock types. Inland from
the coast, glaciofluvial sands and gravels occur extensively to the west of the Spey; to the
east and south till sheets predominate.
This zone provides perhaps the greatest diversity of coastal landforms and active process
environments of any of the natural heritage zones. Reflecting this, of 21 GCR sites selected
for coastal geomorphology interests on mainland Scotland, one-third fall within this zone.
The coastline is one of contrasts. Between Tarbat Ness and Rosemarkie it is rugged and
cliffed, the straight cliff line between these localities coinciding largely with the Great Glen
Fault. Around Tarbat Ness particularly, wave action has sculpted the sandstone bedrock
into an exceptionally diverse array of erosional landforms.
Page 255
10 January, 2002
Between Portknockie and Inverness, shingle landforms dominate the coastal landscape.
Unobstructed fetches to the north-east enable waves to drive shingle westwards along the
coast, most visibly in the form of three magnificent shingle spits at Spey Bay, Culbin and
Whiteness Head. Rates of transport along these bars, although sometimes curtailed by
dredging, are rapid, averaging a few tens of metres per year, if unimpeded, but reaching 100
m per year under exceptional conditions. The shingle source for these spits is partly fed by
fluvial erosion of extensive and exceptionally well-preserved suites of raised shingle storm
beaches lying inland of the Spey and Culbin bars.
From Loch Fleet to the Morrich More, and Lossiemouth to Nairn, sandy beaches and dunes
are also commonplace. Vast accumulations of sand have collected, in particular, around
Morrich More and upon the raised shingle deposits at Culbin; these latter dunes having,
infamously, overwhelmed the coastal community living at Culbin towards the end of the
seventeenth century. Between them, these sites display a broad range of beach- and dunerelated landforms, including barrier beaches, dune ridges, parabolic dunes and blowouts.
Within Loch Fleet, the Dornoch, Cromarty and Beauly Firths and Findhorn Bay, sheltered
conditions prevail. Extensive deposition occurs in all these areas, forming wide expanses of
sandflat, mudflats and saltmarsh. Particularly fine marshes containing a wide array of
topographic features have developed in the lee of Culbin Bar and the barrier beach at
Morrich More. Finally, it is worth noting that the Dornoch Firth is one of the few
completely natural estuaries in the United Kingdom and provides an extremely important
example of estuarine dynamics in an area of falling relative sea level.
The Moray Firth contains the lower reaches and river mouths of a number of major rivers.
In contrast to the upper and middle reaches of the Spey, the lower reaches of the River
Spey are extremely dynamic with a high density of braiding. This site has been described as
being the closest example to a glacial outwash plain found in Britain. The high-energy river
system is related to the steep local gradient that resulted from isostatic uplift after the
retreat of the last ice sheet. The rivers Lossie, Findhorn and Nairn drain to the coast in a
north-east course parallel to the Spey, but do not display the same downstream change in
energy. The course of the Lossie takes two right-angled bends around Elgin, and having been
meandering becomes more sinuous towards the coast. The bends are likely to be related to
geology because the floodplain here is wide and very flat, with much of the downstream
Lossie enclosed within flood embankments. Two canals (Spynie and Innes) drain the flat
coastal plain around Elgin and Lossiemouth. The rivers Findhorn and Nairn are also sinuous
within this flat coastal area, but upstream the Findhorn drains through a narrow meltwater
gorge, known as Randolph’s Leap, which is cut into schist bedrock. During the 1829 flooding
in Moray, the Findhorn reached record heights, ponding upstream of the gorge (which is
thought to be the narrowest constricted bedrock reach on a main river in Britain).
The Moray Firth zone contains the lower reaches of the Ness, the Beauly and the Conon,
which all flow into tidal estuaries. The Beauly meanders tortuously in its lower reaches,
whilst the Conon is more sinuous with some limited division (perhaps reflecting the role of
Lochs Achonachie and Garve upstream in rejuvenating the short river system). The Ness is
still a dynamic river here with the energy to cause significant erosive damage during floods,
and the zone also contains part of Loch Ness and the Caledonian Canal, both significant
water features albeit for different reasons. Outwith the major river systems, there are a
number of minor burns and streams draining to the coast. Standing surface water is
relatively rare, with most of the coastal fringe being sandy and well drained.
Page 256
10 January, 2002
5
Soils
The majority (82%) of soils in this zone are developed on coarse-textured drift material of
Old Red Sandstone origin. Hence they are freely draining, highly leached and have a low
base status, resulting in a large number and variety of podzols. Despite many soils having an
indurated horizon at depth, drainage is still good enough to ensure only limited gleying.
Most soils have been cultivated since Neolithic times and do not display their podzolic
surface horizons, and in some cases organic matter incorporation has resulted in ‘plaggen’
soils. An interglacial soil at Teinland and plaggen and buried arable soils are of national
significance. The soils of this zone are of high agricultural value and hence also at risk from
wind erosion and contamination associated with high intensity agriculture. Soil structural
damage also occurs with inappropriate management and loss of organic matter.
6
Summary of key Earth science features in the Moray Firth
The principal Earth heritage interests in the Moray Firth are summarised in Table 21.1. The Moray
Firth includes a total of 31 GCR sites.
Table 21.1 GCR sites in the Moray Firth
GCR block
No. of sites
Principal interests
Permo-Trias
Non-marine Devonian
Vertebrate Palaeontology
Quaternary of Scotland
3
1
9
9
Fluvial Geomorphology
2
Coastal Geomorphology
7
Representative Permian/Triassic rock sequences
Devonian terrestrial sediments
Fossil remains of Permian/Triassic animals
Quaternary stratigraphy, including rare interglacial
and interstadial deposits; outstanding examples of
glaciofluvial landforms; representative sites for Lateglacial and Holocene relative sea level changes
Slot gorge and the dynamic braided channel of the
Lower River Spey
Large dynamic coastal forelands, shingle bars, rock
coast landforms and saltmarshes
7
Pressures and trends
The potential pressures on different components of the Earth heritage and their vulnerability in
Moray Firth are summarised in Table 21.2. However, there is no systematic information on current
impacts or trends.
Page 257
10 January, 2002
Table 21.2 Potential pressures and vulnerability of Earth heritage interests in the Moray Firth
Earth heritage interest
Vulnerability
Geological interests
Generally robust but may be vulnerable to mineral extraction,
infilling of quarries
Vulnerable to mineral extraction, infilling of quarries; very
vulnerable to irresponsible collecting
Vulnerable to mineral extraction/quarrying; commercial,
industrial and infrastructure developments;
land management changes; construction of tracks;
afforestation; river management
Vulnerable to drainage of bogs and peat extraction
Vulnerable to mineral extraction/quarrying; commercial and
industrial developments; land management changes;
construction of tracks; afforestation; coast defences
Generally robust to all but large scale developments such as
superquarries
Vulnerable to mineral extraction from beaches; coast
coastal forelands, saltmarshes protection; commercial and
industrial developments, land claim and sea level rise
Vulnerable to mineral extraction from beaches; coast
protection; dredging and artificial breaching
Vulnerable to river engineering and management;
afforestation; gravel extraction; land and fisheries
management changes
Vulnerable to land management changes, pollution
Palaeontological interests
Quaternary depositional landforms
and exposures
Palaeoenvironmental records
Records of sea level change
Rock coast features
Beach and dune systems,
and mudflats
Coastal spits and bars
Fluvial geomorphology
Soils
8
State of the resource
Information on individual GCR sites is available from the Earth Science Site Documentation
Reports.
9
Bibliography
Barne, J.H., Robson, C.F., Kaznowska, S.S., Doody, J.P., Davidson, N.C. and Buck, A.L. (1996) Coasts
And Seas Of The United Kingdom. Region 3. North-east Scotland: Cape Wrath to St Cyrus. Joint
Nature Conservation Committee, Peterborough.
Benton, M.J. and Spencer, P.S. (1995) Fossil Reptiles of Great Britain. Geological Conservation Review
Series No. 10. Joint Nature Conservation Committee, Peterborough.
Cleal, C.J., Thomas, B.A., Batten, D.J. and Collinson, M.E. (2001) Mesozoic and Tertiary Palaeobotany of
Great Britain. Geological Conservation Review Series, No. 22. Joint Nature Conservation
Committee, Peterborough.
Comber, D.P.M., Hansom, J.D. and Fahy, F.M. (1994) Culbin Sands, Culbin Forest and Findhorn Bay SSSI:
Documentation and Management Prescription. Scottish Natural Heritage RSM Report No. 14.
Craig, G.Y. (1991) The Geology of Scotland. Scottish Academic Press, Edinburgh.
Dineley, D.L. and Metcalf, S.J. (1999) Fossil Fishes of Great Britain. GCR Series No. 16. Joint Nature
Conservation Committee, Peterborough.
Gauld, J.H. and Puri, G. (2000) Soils and Natural Heritage Zones. Scottish Natural Heritage
Commissioned Report F98AC112 (Unpublished report).
Gemmell, S.L.G., Hansom, J.D. and Hoey, T.B. (2000) The Geomorphology, Conservation and
Management of the River Spey and Spey Bay SSSIs, Moray. Scottish Natural Heritage Research,
Survey and Monitoring Report No. 57.
Page 258
10 January, 2002
Gordon, J.E. and Sutherland, D.G. (1993) Quaternary of Scotland. Geological Conservation Review
Series No. 6. Chapman and Hall, London.
Hansom, J.D. and Black, D.L. (1996) Coastal Processes and Management of Scottish Estuaries. II.
Estuaries of the Outer Moray Firth. Scottish Natural Heritage Review No. 51
Hansom. J.D. and Leafe, R.N. (1990) The Geomorphology of Morrich More: Development of a Scientific
Database and Management Prescription. Dept. of Geography, University of Sheffield. Report to
Nature Conservancy Council, Peterborough.
HR Wallingford, 1996. Shoreline Management Plan. Inverness Firth and part of Moray Firth (Burghead to
Sutors). Unpublished report to Highland Regional Council. HR Wallingford Report EX 3230.
September 1996.
HR Wallingford, 2000. Coastal Cells in Scotland. Cell 3 – Cairnbulg Point to Duncansby Head. Report
to Scottish Natural Heritage, Scottish Office (Agriculture, Environment and Fisheries Dept.) and
Historic Scotland. SNH RSM Report No. 145. Battleby.
Johnstone, G.S. and Mykura, W. (1989) British Regional Geology: The Northern Highlands of Scotland
(fourth edition). British Geological Survey. HMSO, London.
Mather, A.S. and Ritchie, W. (1977) The Beaches of the Highlands and Islands of Scotland. Dept. of
Geography, University of Aberdeen. Countryside Commission for Scotland, Battleby, Perth.
May, V. and Hansom, J.D. in press. Coastal Geomorphology of Great Britain. Geological Conservation
Review Series No. 24. Joint Nature Conservation Committee, Peterborough.
Rafaelli, D. (1992) Conservation of Scottish Estuaries. Proceedings of the Royal Society of Edinburgh,
100B, 55–76.
Ritchie, W., Smith, J.S. and Rose, N. (1978) The Beaches of North-east Scotland. Dept. of Geography,
University of Aberdeen. Countryside Commission for Scotland. Perth.
Sissons, J.B. (1967) The Evolution of Scotland’s Scenery. Oliver and Boyd, Edinburgh.
Sissons, J.B. (1976) Scotland. Methuen, London.
Smith, J.S. and Mather, A.S. (1973) The Beaches of East Sutherland and Easter Ross. Dept. of Geography,
University of Aberdeen. Countryside Commission for Scotland, Perth.
Stapleton, c. and Pethick, J. (1996) Coastal Processes and Management of Scottish Estuaries. I. The
Dornoch, Cromarty and Beauly/Inverness Firths. Scottish Natural Heritage Review No. 50
Steers, J.A. (1973) The Coastline of Scotland. Cambridge University Press, Cambridge.
Stephenson, D. and Gould, D. (1995) British Regional Geology: The Grampian Highlands of Scotland
(fourth edition). British Geological Survey. HMSO, London.
Wright, J.K. and Cox, B.M. (2001) British Upper Jurassic Stratigraphy (Oxfordian to Kimmeridgian)
Geological Conservation Review Series, No. 21. Joint Nature Conservation Committee,
Peterborough.
10
Maps
British Geological Survey Maps: 1:50,000 sheets 83, 84, 85, 93, 94, 95, 102, 103.
Soil Survey of Scotland Maps: 1:250,000 sheet 3 encompasses Zone 21 and coloured 1:63,360 sheets 95,
84, and 94 cover most of the zone. MLURI, Aberdeen.
Page 259
10 January, 2002