Geos 432432-2
Cenozoic tectonism and climates; climate
change
• OrogenyOrogeny-mountain building: existing
mountain belts are the result of Cenozoic
tectonics
Cenozoic tectonism and climate
• Movement of continents to higher latitudeslatitudes-glaciation
more favorable
• Changes in oceanic circulationcirculation-separation of Antarctica,
S. America, Australia (35 my), Ant. Circumpolar current;
closing of Isthmus of Panama (3 my), warm water to N.
Atlantic: The Gateway Hypothesis
• Orographic barriers; Cordilleran mtn.
mtn. ranges; create
deserts and semisemi-arid areas
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Orogenic beltsbelts-1
Island Arc system
Orogenic beltbelt-2
Continental-oceanic
Plate collision
Orogenic beltbelt-3
• ContinentContinent-continent collision: IndiaIndia-Asia
collision to form Himalayas
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• Foreland Thrusting
– Thin skinned; belts of anticlines & synclines
with thin slices of basement rocks: low angle
detachment zone; Appalachian Valley & Ridge
– Thick skinned; Block fault mountain ranges
with basement involvement along steeper
thrust faults; Central Rockies
Extensional tectonics
Sinai Peninsula
Gulf of
Suez
Wadi Isla
Gulf of
Aqaba
El Qaa
Plain
U
D
Red Sea
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Epeirogeny
• Broad uplift or subsidence not associated
with orogenic belts—
belts—broad domes and
basins (Michigan Basin).
Cenozoic climate change
• Gradual Cenozoic cooling
– Circumantarctic current ~ 35 my
– Collision of India and Asia ~35 my
– Closing of Isthmus of Panama ~2~2-3 my
• Quaternary: oscillation between ice house and
greenhouse conditions
Cenozoic tectonism and climate
• Movement of continents to higher latitudeslatitudes-glaciation
more favorable
• Changes in oceanic circulationcirculation-separation of Antarctica,
S. America, Australia (35 my), Ant. Circumpolar current;
closing of Isthmus of Panama (3 my), warm water to N.
Atlantic: The Gateway Hypothesis
• Orographic barriers; Cordilleran mtn.
mtn. ranges; create
deserts and semisemi-arid areas
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CO2 and climate
• Greenhouse effect
• Relationship to tectonics
– Uplift-Uplift-- more rocks exposed to atmospheric CO2 -CO2 consumed-consumed-- climate cools
• Spreading rates: higher spreading rate, more
CO2 released to the atmosphere and climate
warms; lower spreading rates and the opposite
occurs.
Ocean Circulation and climate
Long term gradual cooling
Surface Currents
Ocean Circulation and climate
Cenozoic pattern established 35 my BP
Thermohaline circulation
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Evaluation of the Gateway Hypothesis
• Climate models suggest that the circumcircum-antarctic
•
current and the northern deflection of the Gulf
Stream did not significantly affect climate in the
polar regions; therefore they may not explain
the long term cooling.
At this point, a more likely explanation is that
uplift of the Tibetan Plateau and the Himalayas
caused by the collision of India and Asia may be
responsible for a decrease in CO2 by the
accelerated weathering that takes place there.
The Laurentide Ice Sheet
Short term heating and cooling
Planetary Movements and Cimate
• Eccentricity
• Obliquity
• Precession
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Eccentricity
(100,000 yr)
Obliquity (41,000 yr)
Precession (21,000 yr)
Precession
Approximately 21,000 yr
period
Caused by wobble of the
earth on its axis
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Pleistocene Climates: Greenhouse/Icehouse
fluctuations in high latitudes
Milutin Milankovitch
Major pulse of the ice ages
• Northern hemisphere summers when earth is farthest
from sun—
sun—Now!
• What about the southern hemisphere? Why should it
have a glaciation at the same time (because its summers
now occur when the earth is closest to the sun)
– CO2 feedbackfeedback-the CO2 cycle is in sync with the ice ages, but for
the northern hemisphere it may be an effect of glaciation and
for the southern hemisphere it may be a cause of glaciation
(positive feedback).
– When the earth is colder, the ocean can absorb more CO2.
– During the ice ages, the ocean acts as a carbon pump and
removes CO2 from the atmosphere.
– So when a glaciation starts in the northern hemisphere, CO2
levels drop and the southern hemisphere has a glaciation too??
http://www.globalwarmingart.com/wiki/Image:Milankovitch_Variations_png
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δ 18 O from benthic organisms
δ18O, etc. in Ice Cores
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Pollen records
Other cycles (Dansgard
(Dansgard--Oeshger)
Oeshger)
Younger dryas
What about CO2?
Source: Wikipedia; Timeline of glaciation; CURRENT CO2 LEVELS—380 ppm
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Ruddiman et al., 2005, QSR,
24; 1-10.
The overdue
glaciation
hypothesis
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