Download Geologic Setting and Evolution of Latin America

Geologic Setting and
Evolution of Latin America
Important events in the Geologic
Evolution of Latin America
Formation of the Continental Crust (3.5-0.5Ga)
„ Formation of Gondwana (~600 Ma)
„ Break-up of Pangea (~250 Ma)
„ Break-up of Gondwana (~120 Ma)
„ Formation of the Caribbean (~70 Ma)
„
Geologic History of Latin America
Three kinds of rocks
„
Igneous (cooled from magma)
–
–
–
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Volcanic (cools at surface, ex: basalt)
Plutonic (cools at depth, ex: granite)
Hypabyssal (cools below surface, but at shallow
depth)
Sedimentary (deposited on earth’s surface by
action of water or wind, ex. sandstone,
limestone)
Metamorphic (buried and heated sedimentary
or igneous rocks)
South
American
Geologic
Provinces
Craton, Shield, and Platform
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All refer to the stable interiors of continents
Craton is ancient crust that has long been
stable. Composed of igneous and
metamorphic rocks
Shield is exposed craton
Platform is the craton plus overlying
sediments
South
American
Platform
South American Platform
„
Stable continental crust of S. America not affected by
Cenozoic tectonics and orogenies
–
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„
Basically everything east of the Andes and south of the Caribbean
Consists of Archean and older Proterozoic nuclei
surrounded by younger Proterozoic orogenic belts
Exposed in 4 places:
–
–
–
–
Guyana Shield
Guaporé Shield
Sao Francisco Craton
Rio de la Plata Craton
Topography of the S. American Platform
Precambrian
(>540 Ma)
Exposures in
S. America
Oldest rock in
Latin America:
~3.5 Ga
Orogenies, Orogenic belts, and Orogens
„
Orogenies are episodes of crustal deformation
that generate new crust and mountains
–
–
„
„
Also defined as “Growth of Continental Crust by
addition of material at the margins”
Cratons are not affected.
Orogenic belts are elongate zones of high
relief and deformation, generally mountain
chains like the Andes
Orogens are crustal tracts that were subjected
to orogeny at about the same time.
Two ways to add crust at the margins of continents
„
1) Magmatic additions to the crust
Thick crust beneath Andes is partly due
to addition of magma to base of crust
Much of the high Andes are volcanoes, but not all!
Aconcagua “Fold-and-Thrust” Belt
Aconcagua is the highest mountain in the western hemisphere (6962m or 22841 feet).
It is located in western Argentina, near the Chile border, and about 100 km east of Santiago.
Machu Pichu, Peru
The ruins of Machu Pichu were rediscovered in 1911. The Inca people used the Andean mountain top
(9060 feet elevation) from the early 1400's. The Spaniards never found Machu Picchu, even though they
suspected its existence. Machu Pichu was abandoned some forty years after the Spanish took Cuzco in 1533.
http://www.sacredsites.com/2nd56/21422.html
Two ways to add crust at the margins of continents
„
2) Accretion and collision
Example of accretion: HimalayanTibetan Orogeny
„
Tallest mountain range
in the world
(Himalayas) and
highest plateau
(Tibetan Plateau) are
due to collision of
Indian and Asian
continental crusts
Valdiya 1989
Continued collisions lead to
formation of continent
Precambrian Orogenies
produced the crust of
South America
De Almeida et al. 2000 ESR 50
Lithospheric Root of Craton helps keep it stable
Latin America and the Supercontinent
Cycle
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The supercontinent cycle refers to the episodic
aggregation and dispersal of continental crust
Supercontinent is when most of the continental
crust is found in a single large mass and is
associated with a ‘Superocean’
Supercontinents form as the result of a protracted
period of continent-continent collisions
Cycle takes ~300-400 million years
Three important supercontinents
– 200 Ma, 600 Ma, and 1000 Ma
Most recent Supercontinent: Pangea
End
Precambrian
Supercontinent
The South American Platform assembled when Gondwana
formed at the end of the Precambrian (~550-630 Ma)
pre-730 Ma
A
West
Africa
B
Borborema
W.
Africa
Amazonia
Borborema
BO
Amazonia
volcanic arc
SFC - C
Goiás massif
Brasiliano
Orogeny
Rio de la Plata
São Francisco Congo
continent
cratonic
nucleus
C
AO
R. de la Plata
ca. 730 Ma
D
Neoproterozoic belts
W.
Africa
W.
Africa
Borborema
Amazonia
3
Amazonia
Borborema
4 1 5
2
7
6
Rio de la
Plata
SF-C
ca. 630 Ma
Rio de la
Plata
SFC - C
Kalahari
ca. 550 Ma
A: Cratonic nuclei (pre 730 Ma). B: Initial stage of assembly (collision of Rio de la Plata
Craton with southern part of São Francisco–Congo Craton). BO =Brazilide Ocean, AO =
Adamastor Ocean, SFC-C =São Francisco–Congo Craton. C: Intermediate stage of
assembly (collision of remaining blocks). D: Final assembly. Alkim et al. 2001 Geology
Amazon
Brasiliano
Orogen (~550630 Ma)
cements the
older cratons
into the South
American
platform
S. Marshak (U. Illinois)
0°
São Luis
São
Francisco
Rio de la
Plata
0
1000 km
Andean orogen
Phanerozoic platform/basin
Patagonian platform
exposed Brasiliano
orogens
craton (pre-Brasiliano)
S. America and breakup of Gondwana
Gondwana ~200 Ma ago
ca. 550 Ma
West
Africa
Amazonia
São Fran. W. Congo
Rio de la
Plata
Kalahari
Marshak, U. Illinois
Laurasia = N. America
and Asia
Gondwana = S. America,
Africa, Antarctica, India,
& Australia
Pangea =
Laurasia +
Gondwana
http://pubs.usgs.gov/publications/text/historical.html
S. America and breakup of Gondwana
Gondwana ~200 Ma ago
Global Plate Tectonics
Jurassic to Present Day
By
L.A. Lawver, M.F. Coffin, I.W.D. Dalziel
L.M. Gahagan, D.A. Campbell, and R.M. Schmitz
©2001, University of Texas Institute for Geophysics
February 9, 2001
Breakup of Gondwana produced
Passive Margins on the flanks of
the rifted continents - those
facing the newly formed Atlantic
Ocean
Passive
Margins
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Passive Margins are
equivalent to
Continental shelves
These are not plate
margins but are
important because
they are where thick
accumulations of
sediment occur
Passive Margins are very
important because the thick
accumulation of sediments holds
much of the world’s future
supply of oil and gas
The Gulf of Mexico Passive Margin
Texas
Mexico
Patty Ganey, UTIG
The Gulf of Mexico
(and Central
Atlantic) opened
along the
Carboniferous
Suture between
Gondwana and
Laurasia
Configuration at end of Paleozoic
(~245 Ma) after Walper, 1972
Opening of the Gulf of Mexico and Evolution of the
Mojave-Sonora Megashear. This moved Mexico into
its modern position.
N. America
Mojave-Sonora
Megashear
S. America
Passive Margins of the World
Moores & Twiss 1995
A Passive
Margin in
the
making:
The Gulf
of
California
that began
opening
recently
(about 5
Ma. Ago).
Evolution of the Caribbean
S. America
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Evolution of the Caribbean
S. America