208_Lect15_color - Paleoclimate of Cenozoic • Notice the...

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Unformatted text preview: Paleoclimate of Cenozoic • Notice the ocean circulation: – Tethys seaway is open – As is the Isthmus of Panama – Efficient Heat Transfer • Note that the Circum-Antarctic current is not yet flowing Paleocene Antarctic Forams show O, C isotope shifts • Oxygen shifts to lighter values – Indicates rapid warming of oceans (<3000 years) – T~18ºC near the arctic! • Carbon shifts to lighter values – Strange - should become heavier if oceans are warm (sequester organic carbon) – Must be a massive release of methane from hydrates Carbon Interesting result of Eocene warming: • Tropical conditions extend to >50º latitude – British Isles and Alaska covered in Rain Forests • So, warming not from CO2 (forests would consume it) – Rather from methane and water vapor released by transpiration of huge forests • Warming of oceans causes a mass extinction of ~70% of marine Forams 1 Oligocene Cooling event: Beginning of Current Ice Age • O-isotopes in forams shift to Heavy values from (1) cooling of oceans and (2) growth of glaciers – Rapid ~100,000 years • Note: this happens again late in the Pliocene. Hmm… Cause of Oligocene Cooling: • Rifting of Australia from Antarctica – Opens Circumpolar current – This current cools the continent and grows today’s ice sheets Result of Circumpolar Current and glacier growth: • Antarctic Bottom Water begins to form (Wiedel Sea opens as SA Wiedel Sea moves away) – This atmospheric cooling causes a mass extinction of the tropical forests and animals adapted to live in them. • Change to modern world: Grasslands dominate because arid climate zones become most prevalent zone – Why arid? Loss of rainforest reduces amount of atmospheric H2O from transpiration 2 Further cooling in Miocene • Separation between Antarctica and SA and Aus. Becomes wider and DEEPER • Deeper, colder circulation cools oceans at lower latitude (mixing of currents) • Results: Cooler oceans and more arid climates Final thing for the Final Exam • Know that our family Hominidae branched from early apes between 5 and 8 Ma. • Know that our species Homo sapiens evolved Know Homo in Africa ~150,000 ybp in ybp 3 ...
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This note was uploaded on 05/26/2011 for the course GEOL 208 taught by Professor Michaelstuart during the Spring '11 term at University of Illinois, Urbana Champaign.

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