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GeosGeos 432432--22

Cenozoic Cenozoic tectonismtectonism and climates; climate and climates; climate changechange

•• OrogenyOrogeny--mountain building: existing mountain building: existing

mountain belts are the result of Cenozoic mountain belts are the result of Cenozoic

tectonicstectonics

Cenozoic Cenozoic tectonismtectonism and climateand climate

•• Movement of continents to higher latitudesMovement of continents to higher latitudes--glaciationglaciationmore favorablemore favorable

•• Changes in oceanic circulationChanges in oceanic circulation--separation of Antarctica, separation of Antarctica, S. America, Australia (35 my), Ant. Circumpolar current; S. America, Australia (35 my), Ant. Circumpolar current; closing of Isthmus of Panama (3 my), warm water to N. closing of Isthmus of Panama (3 my), warm water to N. Atlantic: Atlantic: The Gateway HypothesisThe Gateway Hypothesis

•• OrographicOrographic barriers; Cordilleran barriers; Cordilleran mtnmtn. ranges; create . ranges; create deserts and semideserts and semi--arid areasarid areas

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OrogenicOrogenic beltsbelts--11

Island Arc system

OrogenicOrogenic beltbelt--22

Continental-oceanic

Plate collision

OrogenicOrogenic beltbelt--33

•• ContinentContinent--continent collision: Indiacontinent collision: India--Asia Asia

collision to form Himalayascollision to form Himalayas

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•• Foreland ThrustingForeland Thrusting

–– Thin skinned; belts of anticlines & synclines Thin skinned; belts of anticlines & synclines

with thin slices of basement rocks: low angle with thin slices of basement rocks: low angle

detachment zone; Appalachian Valley & Ridgedetachment zone; Appalachian Valley & Ridge

–– Thick skinned; Block fault mountain ranges Thick skinned; Block fault mountain ranges

with basement involvement along steeper with basement involvement along steeper

thrust faults; Central Rockiesthrust faults; Central Rockies

Extensional tectonicsExtensional tectonics

Sinai Peninsula

Red Sea

Gulf of

Suez

El QaaPlain

Gulf of Aqaba

Wadi Isla

UD

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EpeirogenyEpeirogeny

•• Broad uplift or subsidence not associated Broad uplift or subsidence not associated

with with orogenicorogenic beltsbelts——broad domes and broad domes and

basins (Michigan Basin).basins (Michigan Basin).

Cenozoic climate changeCenozoic climate change•• Gradual Cenozoic coolingGradual Cenozoic cooling

–– CircumantarcticCircumantarctic current ~ 35 mycurrent ~ 35 my

–– Collision of India and Asia ~35 myCollision of India and Asia ~35 my

–– Closing of Isthmus of Panama ~2Closing of Isthmus of Panama ~2--3 my3 my

•• Quaternary: oscillation between ice house and Quaternary: oscillation between ice house and greenhouse conditionsgreenhouse conditions

Cenozoic Cenozoic tectonismtectonism and climateand climate

•• Movement of continents to higher latitudesMovement of continents to higher latitudes--glaciationglaciationmore favorablemore favorable

•• Changes in oceanic circulationChanges in oceanic circulation--separation of Antarctica, separation of Antarctica, S. America, Australia (35 my), Ant. Circumpolar current; S. America, Australia (35 my), Ant. Circumpolar current; closing of Isthmus of Panama (3 my), warm water to N. closing of Isthmus of Panama (3 my), warm water to N. Atlantic: Atlantic: The Gateway HypothesisThe Gateway Hypothesis

•• OrographicOrographic barriers; Cordilleran barriers; Cordilleran mtnmtn. ranges; create . ranges; create deserts and semideserts and semi--arid areasarid areas

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COCO2 2 and climateand climate

•• Greenhouse effectGreenhouse effect

•• Relationship to tectonicsRelationship to tectonics–– UpliftUplift---- more rocks exposed to atmospheric COmore rocks exposed to atmospheric CO2 2 ----COCO22 consumedconsumed---- climate coolsclimate cools

•• Spreading rates: higher spreading rate, more Spreading rates: higher spreading rate, more COCO22 released to the atmosphere and climate released to the atmosphere and climate warms; lower spreading rates and the opposite warms; lower spreading rates and the opposite occurs.occurs.

Ocean Circulation and climateOcean Circulation and climateLong term gradual coolingLong term gradual cooling

Surface Currents

Ocean Circulation and climateOcean Circulation and climateCenozoic pattern established 35 my BP Cenozoic pattern established 35 my BP

Thermohaline circulation

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Evaluation of the Gateway HypothesisEvaluation of the Gateway Hypothesis

•• Climate models suggest that the circumClimate models suggest that the circum--antarcticantarcticcurrent and the northern deflection of the Gulf current and the northern deflection of the Gulf Stream did not significantly affect climate in the Stream did not significantly affect climate in the polar regions; therefore they may not explain polar regions; therefore they may not explain the long term cooling.the long term cooling.

•• At this point, a more likely explanation is that At this point, a more likely explanation is that uplift of the Tibetan Plateau and the Himalayas uplift of the Tibetan Plateau and the Himalayas caused by the collision of India and Asia may be caused by the collision of India and Asia may be responsible for a decrease in COresponsible for a decrease in CO22 by the by the accelerated weathering that takes place there.accelerated weathering that takes place there.

The The LaurentideLaurentide Ice SheetIce SheetShort term heating and coolingShort term heating and cooling

Planetary Movements and Planetary Movements and CimateCimate

•• EccentricityEccentricity

•• ObliquityObliquity

•• PrecessionPrecession

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Eccentricity

Obliquity (41,000 yr)

Precession (21,000 yr)

(100,000 yr)

PrecessionPrecession

Approximately 21,000 yr

period

Caused by wobble of the

earth on its axis

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MilutinMilutin MilankovitchMilankovitch

Pleistocene Climates: Greenhouse/Icehouse fluctuations in high latitudes

Major pulse of the ice agesMajor pulse of the ice ages

•• Northern hemisphere summers when earth is farthest Northern hemisphere summers when earth is farthest from sunfrom sun——Now!Now!

•• What about the southern hemisphere? Why should it What about the southern hemisphere? Why should it have a have a glaciationglaciation at the same time (because its summers at the same time (because its summers now occur when the earth is closest to the sun)now occur when the earth is closest to the sun)–– COCO22 feedbackfeedback--the COthe CO22 cycle is in sync with the ice ages, but for cycle is in sync with the ice ages, but for the northern hemisphere it may be an effect of the northern hemisphere it may be an effect of glaciationglaciation and and for the southern hemisphere it may be a cause of for the southern hemisphere it may be a cause of glaciationglaciation(positive feedback).(positive feedback).

–– When the earth is colder, the ocean can absorb more COWhen the earth is colder, the ocean can absorb more CO22. .

–– During the ice ages, the ocean acts as a carbon pump and During the ice ages, the ocean acts as a carbon pump and removes COremoves CO22 from the atmosphere. from the atmosphere.

–– So when a So when a glaciationglaciation starts in the northern hemisphere, COstarts in the northern hemisphere, CO22levels drop and the southern hemisphere has a levels drop and the southern hemisphere has a glaciationglaciation too??too??

http://www.globalwarmingart.com/wiki/Image:Milankovitch_Variations_png

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δ 18 O from benthic organisms

δδ1818O, etc. in Ice CoresO, etc. in Ice Cores

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Pollen recordsPollen records

Other Other cycles (cycles (DansgardDansgard--OeshgerOeshger))

Younger dryas

Source: Wikipedia; Timeline of glaciation; CURRENT CO2 LEVELS—380 ppm

What about CO2?

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Ruddiman et al., 2005, QSR, 24; 1-10.

The overdue glaciation

hypothesis