Download Glacial deposits

Geology Gallery
Geological Map of the Cromer Area
Overstrand Chalk Raft
The huge chalk rafts
that dominate the cliffs
at Overstrand.
The Cromer Ridge is a huge glacial feature which
forms the highest point in Norfolk. The ridge is
what’s left of the terminal moraine, formed as the
glacier retreated. The eastern part of the ridge is
a push moraine. This is best seen at Overstrand,
which has a 60 metre cross-section through the
ridge, showing spectacular ‘rafts’ of chalk which
were pushed into their current position by glacial
movement.
N
5
2
The western part of the ridge is composed of
outwash sands and gravels deposited by rivers at
the glacier edge. This is best seen at Telegraph
Hill. At the view point there is a steep northwardfacing slope which would have been the glacier
margin, this rests on the flat-lying outwash gravel
surface of Kelling Heath. There are also a series of
circular hills known as kames between Telegraph
Hill and the sea.
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7
4 Weybourne
8 Blakeney
Glacial Sand and
Gravel
Glacial Till
Cromer Forest-bed
Formation
White Chalk
Wroxham Crag
Formation
Beach Sand
and Gravel
Terminal moraine = sediments deposited by a
glacier at its end when the ice was at its maximum
extent.
West Runton Cliffs
Photograph of the cliffs at West Runton
beach, highlighting the major geological
formations.
© Martin Warren
Wroxham Crag
Formation
Cromer Forest-bed
Formation
Alluvial sand and
gravel
Silurian
Crag deposits = a series of marine deposits at
the base of the Pleistocene in Norfolk, Suffolk and
Essex. Crag is a local word for shelly sand.
Kame = sand and gravel hills formed as glaciers.
retreat.
7 Cley
Permo- Triassic Jurassic
Triassic
4
Cromerian Stage = a stage within the Pleistocene
Period, from 866,000 to 478,000 years ago.
Push moraine = a broad arc-shaped ridge of
material pushed along by an advancing glacier.
3 Sheringham
3
Glossary:
Outwash = glacial sediments deposited by
meltwater at the terminus of a glacier.
6 Holt
Glacial Till
White Chalk Group
Lower Cretaceous
Sandstone
8
Glacial deposits = the rocks, soil and other
sediment picked up and transported by glaciers.
2 Cromer
Cretaceous
S
W
5 Telegraph Hill
Exaggerated relief geological map of
Cromer and the surrounding area.
Showing the Cromer Ridge, which at
about 100 metres above sea level, is the
highest point in the whole of Norfolk.
1
E
1 Overstrand
Pleistocene
The rocks around Cromer are of international
importance, not least because the Cromer Forestbed Formation at West Runton is the ‘type locality’
for the Cromerian Stage. The Chalk and Crag
deposits which can be seen along the beaches of
North Norfolk are also of world importance. Above
these sediments however, are the glacial deposits
which were laid down starting approximately
500,000 years ago, during the Ice Age. These form
most of the cliffs that you can see along the coast
at Trimingham, Sidestrand and Overstrand.
Holocene
Key
Lias Mudstone
Mercia Mudstone
Sherwood Sandstone
Group
Metamorphosed
Mudstone, Siltstone
and Sandstone
Ice coverage in the
British Isles during the
most recent glaciation
(between about 110,000
to 10,000 years ago).
The Cromer Ridge is one
feature caused by the
movement of ice during
this glaciation.