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Lecture 10

Lecture 10

8 Pages
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Department
Environmental Science
Course Code
EESA06H3
Professor
Nick Eyles

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EESA06 Lecture 10 Page 1
EESA06 Lecture 10
Canadas Geologic Journey: The Last 4 Billion Years
1. Continents grow through time by obduction
2. North American continent shows 5 growth stages:
a) Arctica (2.7 Ga) oldest Giganum (Billion)
b) Columbia (1.8 Ga)
c) Rodinia (1.0 Ga)
- a + b +c = Canadian Shield (the craton) the old hard core rocks, rigid
d) Pangea assembly (350 Ma): Maritime Canada is added during Appalachians Orogeny
(Appalachian Mountains) added sedimentary + highly fossil rocks
e) Pangea breakup (<200 Ma): British Columbia is added during Cordilleran Orogeny (e.g.
Rockies)
Geology of North America known for 100 years but what put it together?
Brown old hard core ( Ontario+ Quebec area)
Blue apolation belt maritime Canada
Zircons:
2.7 billion year old zircons Uranium + Lead
dating
Age rings, amount of lead in the crystals
Tom crow expert on dating rocks
Detrital Secondary, having be derived from
something else
Detritous - Garbage
Acasta Gneiss (NWT):
4 billion years old near Yellowknife
The oldest continental crust found so far?
Zircons: from igneous rocks, weathered,
zircons released, become sedimentary rock then metamorphosed into a gneiss
Continents grow thru time similar to Swiss roll
older stuff in the middle
Deconstructing North America:
1)The original NA continent, Arctica which
started to form about 2.5 billion years ago
from smaller continents and was completed
by about 1.9 billion years ado when old
Archean cratons (ex: Slave, Nain provinces)
were welded together by the Trans-Hudson
Orogen and others
2)Added to the North American continent
during the formation of Nena about 1.8
billion years ago after the Penokean Orogeny
www.notesolution.com
EESA06 Lecture 10 Page 2
3)Added During the Formation of Rodinia about 1.3 billion years ago during the
Grenville Orogeny
4)Added during the formation of Pangea about 600 million-300 million years ago
Appalachian Mt
5)Added after the breakup of Pangea about 250 million years ago Corillera
Provinces not politics, rocks that stretch over large areas fairly similar in appearance,
have very sharp boundaries (ex: Superior Province, Hern Province, Nain Province)
Orogen the rocks that result from orogeny, highly deformed rocks (ex: most common =
gneiss)
Provinces seem to be separated by orogens (ex: Himalaya)
Green stone belts metamorphosed old ocean rocks
Slave Province true core of Canadian shield, Yellowknife area, oldest part of North
American continent
Greenland broke of about 80million years ago, separated by a failed rift
Craton old rocks that make up the rigid interior of the continent
Lithoprobe dancing elephants, has a large plate which create strong vibrations to mimic
earthquakes
Help reconstruct earths surface up to 70km
Seismic Transsects cross-sections of shield over long distances
Canadian Shield peneplain (almost a plain/flat), no mountains, has been eroded
Labrador is added to Canada
Cartoons
Ancient earth behaved similar to present day
Confirms uniformitarianism
Might have been faster in past earth was
warmer, hotter mantle
Political Unificiation of the Provinces 1867 to 1949
Driving the Golden spike November 1885
Canadian Pacific Railroad
An analog for welding of geological provinces
through geologic time
Cratonization: the building of cratons/shields
Obduction: The Accretionary Process that
builds continents from smaller crustal blocks
Greenstone Belt green rocks, metamorphosed
basalt amphibolites
Superior Craton a lot of mineral wealth
Hydrothermal processes near mid-ocean
ridges
Great thickness of Pillowed Basalts between blocks of
continental crust at Yellowknife (a lot of Gold)
www.notesolution.com
EESA06 Lecture 10 Page 3
Simple bacterial filaments at c. 3.3 Ga - Australia
Gunflint Chert (oldest bacteria in Ontario) c. 1.1 Ga
Stromatolites bacterial colonies, like hypersaline lagoons, no predators, Shark Bay
Western Australia
Sudbury Meterorite Crater 2 billion years ago Nickel rich
Big depression in the surface of the shield
Once thought to be volcanic but actually is a product of a large meteorite strike (2nd
largest) 10km diameter
Largest is in South Africa
Oval has been squeezed by oduction during the Grenville Orogeny
Fractures are softer rocks caused by many things
Wanapikei Lake younger meteorite crater, 37 million
year old
Sudbury
Cone structures shatter corners
Surround the crater, record intense impact stresses
created by the meteorite strike
Ontario 1 billion years ago: the Greenville mountains,
very high
Group of seven painted the current shield,
peneplain
South America that was colliding with North
America = Grenville Orogeny
Gneiss the most common Canadian rock?
oFormed 20km down, below high mountains,
have been eroded expose gneiss rocks
oPink is more granitic, more feldspar
oDarker horn-blend
oExfoliation unleaf layers, spall off
Grenville Orogeny the final building of the Canadian
shield
Area in green exposed shield, on the surface
Most of it under United States
The First multicellular life: The Ediacara Fauna (550-
500Ma):
Cambrian Explosion sudden appearance of
advanced life forms
Burgess Shale: Walcotts Quarry, Yoho National
Park
Mistaken point Fm: Newfoundland
Wonderful Life by Steven J Gold
orole of chance in evolution
www.notesolution.com

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Description
EESA06 Lecture 10 Page 1 EESA06 Lecture 10 Canadas Geologic Journey: The Last 4 Billion Years 1. Continents grow through time by obduction 2. North American continent shows 5 growth stages: a) Arctica (2.7 Ga) oldest Giganum (Billion) b) Columbia (1.8 Ga) c) Rodinia (1.0 Ga) - a + b +c = Canadian Shield (the craton) the old hard core rocks, rigid d) Pangea assembly (350 Ma): Maritime Canada is added during Appalachians Orogeny (Appalachian Mountains) added sedimentary + highly fossil rocks e) Pangea breakup (<200 Ma): British Columbia is added during Cordilleran Orogeny (e.g. Rockies) Geology of North America known for 100 years but what put it together? Brown old hard core ( Ontario+ Quebec area) Blue apolation belt maritime Canada Zircons: 2.7 billion year old zircons Uranium + Lead dating Age rings, amount of lead in the crystals Tom crow expert on dating rocks Detrital Secondary, having be derived from something else Detritous - Garbage Acasta Gneiss (NWT): 4 billion years old near Yellowknife The oldest continental crust found so far? Zircons: from igneous rocks, weathered, zircons released, become sedimentary rock then metamorphosed into a gneiss Continents grow thru time similar to Swiss roll older stuff in the middle Deconstructing North America: 1) The original NA continent, Arctica which started to form about 2.5 billion years ago from smaller continents and was completed by about 1.9 billion years ado when old Archean cratons (ex: Slave, Nain provinces) were welded together by the Trans-Hudson Orogen and others 2) Added to the North American continent during the formation of Nena about 1.8 billion years ago after the Penokean Orogeny www.notesolution.com
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