Download Geology of the Kingston Area – 1.1 Billion Years of History

GeoEngineering Centre Field Trip 2013
Geology of the Kingston Area
1.1 Billion Years of Earth History
South
China
Seychelles India
Kalahari
Baltica
Laurentia
East
Antarctica
P
Siberia
A v alo nian
Rio
Plata
Amazonia
Congo
T i m 30°S
ani
an
Cado
mi a
n
M
vic
ian
West
Africa
60°S
The Supercontinent Rodinia
750 Million Years Ago...
Siberia
250 million years ago
Pangaea
Baltica
30°N
North
China
Laurentia
Palaeotethys
South
China
Equator
a
ld
or
ring the Ordo
iod
er
W
Madagascar
du
ap
30°N
North
China
Australia
West Afric
Miller Museum of Geology,
Miller Hall, Queen’s University
Amazonia
ot
Ne
ys
eth
Gondwana
30°S
Congo
Rio
India
Pl
a ta
Kalahari
East
Antarctica
Subduction zones
Australia
60°S
Seafloor spreading axis
Field Trip Background Info: Minerals and Rocks
The 8 most abundant elements in the Earth’s crust by
weight % are:
Rock-forming Minerals and their Properties
Although there are thousands of different kinds of
minerals, many rocks are only made up of a few
common rock-forming minerals. Quartz, feldspar, and
mica are common silicate minerals that are found in
the igneous, sedimentary, and metamorphic rocks that
we will see on the field trip in the afternoon. Calcite is
a common carbonate mineral that we will see in
several rocks as well.
Mica:
Oxygen (O)
Silicon (Si)
Aluminum (Al)
Iron (Fe)
Calcium (Ca)
Sodium (Na)
Potassium (K)
Magnesium (Mg)
Microcline Feldspar:
46.6%
27.7%
8.1%
5.0%
3.6%
2.8%
2.6%
2.1%
Most of the common rock-forming minerals of the
crust are silicates (based on silicon and oxygen
compounds).
Quartz:
The Mohs Hardness Scale of Minerals
Calcite:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Hematite:
Amphibole:
Classification of Rocks
Talc
Gypsum
Calcite
Fluorite
Apatite
Orthoclase
Quartz
Topaz
Corundum
Diamond
(Hardness of glass plate ~5.5)
The Rock Cycle
Rocks are made up of different kinds of minerals.
The types of minerals, and the way that the rock
formed, can be used to determine the environment in
which the rock formed.
Igneous
and recrystalli
zat
lting
ion
Me
Igneous Rocks: Rocks formed from cooling molten
liquids either intruded into the Earth’s crust or
extruded on the surface of the Earth.
Magma/Lava
ring
athe
we
eating
Chemical
and/or
Mechanical
Sediments
Bu
rh
d/o
an
iral
Metamorphic
Changes due
to Heat and
Pressure
dl
an
ithi
ficat
ion
– Page 1–
n
The Earth is the ultimate recycler, and the rocks are
converted from one type to another by natural geological
processes over long time periods. Although nothing much
seems to happen to the rocks in our lifetimes, if we could
watch them over millions of years we would see
tremendous changes in the rocks.
or chemi
cal
d
e
po
sit
io
Sedimentary Rocks: Rocks formed from cementing
of mechanically weathered sediments, or from
chemically precipitated sediments.
Metamorphic Rocks: Rocks formed under
tremendous heat and/or pressure.
(Hardness of fingernail: ~2.5)
Sedimentary
Field Trip Preparation: Geological History of Kingston
The Grenville Mountains of Kingston: 1.3 Billion Years Ago.
1.8 - 1.3 billion years ago
Laurentia
The oldest rocks in the Kingston area are the
metamorphic and igneous rocks of the Grenville
Province of the Canadian Shield. They started out
as sediments in an ocean over 1.3 billion years ago,
and they were metamorphosed during the formation of
a supercontinent called Rodinia. The eroded roots of
the mountain range that formed in this area due to
continental collisions at that time underlie the entire
Kingston region.
Shallow Sea
(Proto-North America)
(Covering present-day Kingston area)
Er
os
ion
Ocean
Sandstone, conglome
rate
mudstone,
Limestone
Eroding mountains near present-day Sudbury, Ontario,
deposit sediments in a shallow sea near present-day
Kingston. Limestone forms in the ocean offshore.
1.3 billion - 950 million years ago
South
China
Grenville Orogeny
Seychelles India
Metamorphic gneiss, schist,
quartzite, and marble
Madagascar
Igneous
Plutons
Kalahari
Collisions with other ancient continents produced the
Grenville Mountains, folding and metamorphosing the
pre-existing sediments. Igneous rocks intrude forming
plutons, dykes and sills.
East
Antarctica
Laurentia
Siberia
Rio
Plata
Amazonia
Congo
500 million years ago
(Proto-North America)
Baltica
Laurentia
Grenville Province
Igneous
Dykes
A v alo nian
Igneous
Dykes
30°N
North
China
Australia
West
Africa
Cado
mi a
n
Laurentia
(Proto-North America)
T i m 30°S
ani
an
60°S
Igneous
Plutons
Metamorphic gneiss, schist,
quartzite, and marble
The Supercontinent Rodinia
around 750 million years ago.
By 500 million years ago, the Grenville Mountains were
Approximate
eroded
to their roots.Major Plate Boundaries
Water World: Kingston in the Ordovician
During the Cambrian and Ordovician Period, ocean
levels were high on the Earth. Periodically during
these times, North America was covered by water
forming a distinctive sequence of rocks.
The geography of the Earth was quite different during
the Ordovician, as shown by the paleogeographic
reconstructions of Dr Ron Blakey of Northern Arizona
University.
Ice Age: Kingston 18 000 years ago
The Earth’s climate began to cool dramatically around
1.6 million years ago. At least 4 times in the last one
million years, the Kingston area has been completely
covered by glacial ice. The last major ice sheet, the
Wisconsin advance, covered this area until only about
10 000 years ago.
– Page 2–
Field Trip Preparation: Plate Tectonics
Outline of the Major Tectonic Plates of the Earth
Eurasian
Plate
Eurasian
Plate
North American
Plate Atlantic
Pacific Plate
Mid-Ocean
Ridge
Cocos
Plate
Nazca
Plate
Indian-Australian
Plate
African
Plate
South American
Plate
Antarctic Plate
Simplified Summary of Plate Tectonic Activity
Mid-Ocean Ridge
(Divergent Plate Margin)
Island Arc
Volcano
Continental Rift Zone
(Newly-Forming Plate Boundary)
Subduction Zone
“Hot Spot”
Volcano
(Convergent Plate Margin)
Trench
Trench
Continental Crust
Oc
ea
At subduction zones,
the crust melts as it sinks
back into the Earth again.
“Hot Spot”
nic
Cr
us
t
Rising magma
adds new ocean
crust at ridges
The movement of the plates is related to heat flow inside of the Earth. At mid-ocean ridges, underwater
volcanoes add new ocean crust. At trenches, the ocean crust sinks down into the mantle again. “Hot
spots” may be the cause of isolated volcanic island chains in the middle of the ocean (like the Hawaiian
Islands).
– Page 3–
3
4
5
6
Legend
PALEOZOIC
ORDOVICIAN Period Sedimentary Rocks
Black River & Trenton Groups
Limestone.
13
Beekmantown Group
Dolomite and sandstone.†
12
LOWER ORDOVICIAN OR CAMBRIAN Sedimentary
Potsdam or Nepean Formation
Sandstone.
11
UNCONFORMITY
PRECAMBRIAN
PLUTONIC ROCKS (Igneous Rocks)
10
9
8
7
Diabase or porphyritic andesite dikes.
Granitic gneiss, migmatite, granitized
gneiss, hybrid granite gneiss, granite
pegmatite.
Granite and syenite.
Grey granite, granite gneiss,
granodiorite, tonalite.
Diorite, gabbro, anorthosite, metagabbro, amphibolite.
INTRUSIVE CONTACT
METASEDIMENTARY ROCKS
2
(Metamorphic Rocks formed from Sediments)
5
Quartzite, quartzo-feldspathic rocks.
4
Paragneiss, pelitic and psammo-pelitic
schists and gneisses.
3
Marble, lime silicate rocks, skarn.
2
Para-amphibolite, biotite-amphibole
schists and gneisses.
1
Geology of Kingston
Field Trip Route
September 2013 Version
– Page 4–
Stop #1
Barriefield Hill Roadcut.
Sea Level Rise.
Barriefield Hill is a gentle limestone anticline - an arch made of dipping sedimentary layers which have the
youngest layers at the top of the crest and the oldest layers in the core of the arch. An upside down arch
with the oldest layers on the bottom is called a syncline.
One of the principles of stratigraphy (the study of sedimentary rock layers) says that sedimentary beds are
originally deposited in flat, horizontal layers. So how did these layers become curved? Two possibilities
exist: 1/ the flat layers were subjected to a force that folded or bent them; or 2/ the layers were deposited
over a “bump” in the older basement rock and subsequent compaction over the basement high has
accentuated the draping effect. There is evidence for both possibilities in this outcrop. In the south-side
ditch halfway up the hill near the core of the anticline, there is an exposed “knob” of billion year old quartzite
and gneiss. This resistant rock could be the basement high that the limestone layers draped over as mud
was deposited from the seawater 470 million years ago. Since nothing is simple in geology however, there
is evidence further up the hill (in the form of pressure-solution produced stylolites) that shows that there
could have been pressure directed in an east-west sense that may have also slightly folded the sedimentary
layers into the present anticlinal form.
Stylolites
Pressure
Direction
Stylolites are surfaces in the rock where it
has dissolved due to high directed pressure.
When viewed from the side, the dissolution
surface line resembles blocky “turret” shapes
in the rock.
1 cm
Gentle Anticline
Quartzite/Gneiss Core
at the base of the
anticline.
– Page 5–
Stop #2
A mole-hill out of a mountain...
Abbey Dawn Roadcut.
The oldest rocks in the Kingston area (the “basement rocks”) are approximately 1.1 billion year old
metamorphic rocks of the Canadian Shield. They formed when our part of North America (Laurentia)
collided with part of South America (Amazonia). The collision produced a Himalaya-scale mountain range
called the Grenville Mountains running through this area around a billion years ago. Pre-existing
sedimentary rocks were changed (metamorphosed) due to the heat and pressure: sedimentary limestone
became metamorphic marble, sandstone became quartzite, and impure mixtures of mud and sand became
gneiss.
As tectonic forces changed, the mountain-building pressures eased and weathering took over. By about 500
million years ago, the mountain range was completely eroded away leaving a barren rocky surface covered
with sand, gravel and boulders. Land plants had not yet appeared on the Earth, and the land would have
been bleak and barren. Harder rock ridges and knobs made up predominantly of quartzite would have
been more resistant to erosion, and so some topographic relief would have been present in the area. Today,
these resistant rocks are responsible for the area’s world famous 1000 Islands Region.
The outcrop at the Abbey Dawn Road illustrates beautifully the response of different rock types to erosion,
and shows the sequence of events in the region between 1 billion and 500 million years ago. At the north
end of the outcrop, the rock is a very resistant quartzite, which stands higher than the south end which is
predominantly softer gneiss that more easily eroded away. At the very south end of the outcrop is a
prominent angled layer of boulders, overlain by flat-lying layers of limestone from about 470 million years
ago. The fact that the limestone beds are still horizontal indicates that it hasn’t been disturbed since being
deposited as layers of mud on an ocean floor around 470 million years ago. This implies that the whole
outcrop shows the original orientation of the rocks when sea levels rose. The quartzite to the north was a
“hill” left over from the erosion of the Grenville Mountains. Boulders rolled down the hill to the south,
creating a talus slope of angular boulders against the south slope of the hill. Finally, as sea levels rose,
layers of lime mud were deposited against the boulder layer, eventually becoming limestone.
Since the quartzite and gneiss is around 1 billion years old, and the limestone is about 470 million years old,
the 1-2 metre layer of boulders represents an erosional time gap (an unconformity) of at least 500 million
years!
Undisturbed flat-lying limestone
500 million years
of erosion!
Talus-slope boulder layer
(conglomerate)
Unconformity surface
(a “non-conformity”)
Gneiss (south end) next
to quartizite “hill” (north end)
– Page 6 –
Stop #3
Can you handle the pressure...
Hwy 15 and Sunbury Road Roadcut.
During the mountain building episode, pre-existing
limestone was metamorphosed to marble. Just as
rocks respond differently to weathering (as seen at the
Abbey Dawn roadcut) rocks also respond differently to
the heat and pressure of metamorphism. In this outcrop,
the marble behaved like wax, easily bending and flowing
under the pressure. Pieces of brittle gneiss behaved
differently, first folding and then breaking into pieces that
are now seen “floating” in the surrounding marble.
Within the marble, grey-metallic grains of graphite can
be found, which formed during the metamorphism from
organic carbon that was buried in the original limestone.
Fragments of brittle
gneiss surrounded
by softer marble
Folded gneiss
Stop #4
Rivers flowing across a barren land...
Sunbury Road.
The world of 500 million years ago was a much different
place. Permanent land life had not yet appeared on the
Earth (neither plants nor animals) and the continents
were barren and wind-swept. Sands from the
weathering of the Grenville Mountains would have been
blown by winds, and washed by streams meandering
across the landscape. Here, the sandstone is thinly
bedded and cemented partially with the mineral
hematite (red iron oxide) indicating that it was probably
deposited on land in a river system. Pebble layers
possibly indicate floods that winnowed away the finer
sand, leaving only the heavier sediments. Other
sandstones in the Kingston area were originally
deposited in huge dunes, or on tidal-flat beaches near
the slowly rising oceans from 470 million years ago.
– Page 7 –
Stop #5
Dykes and Plutons...
Sunbury Road.
In addition to metamorphism, the mountain building
episode was accompanied by volcanism as well. Cracks
opened up by the pressures of continental collision were
filled with hot magma from below. At this outcrop, black
basaltic magma filled cracks in the white quartzite
forming numerous diabase dykes cutting through the
rock.
At the west end of the outcrop, a larger intrusive white
granite can be found. Even larger intrusions (plutons) of
pink granitic rock can be seen throughout the area,
forming features such as Foley Mountain in Westport,
Ontario.
Black diabase dyke in white quartzite
Stop #6
Crosscutting Relationships
Inverary.
Number the rocks and the events from oldest (1) to youngest (7) on this
schematic diagram of the outcrop.
Sketch a normal fault and a
reverse fault.
Limestone
Disconformity (Sea Level Rise)
Rideau Grit (Arkose Sandstone)
Nonconformity (Erosion)
Precambrian Quartzite/Gneiss
F
ke
Dy
au
lt M
ov
e
ke
Dy
me
nt
– Page 8 –