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Cenozoic. Tectonics Climate. The Himalayas. The Closing of the Tethys. As the World Warms: 65 Million Years of Hot and Cold. As the World Warms……. The Geologic Evidence The Heartbeat of Climate The Present and Future. The Geologic Evidence. Paleontological and Paleobotanical Remains.
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Cenozoic Tectonics Climate
As the World Warms……. • The Geologic Evidence • The Heartbeat of Climate • The Present and Future
The Geologic Evidence • Paleontological and Paleobotanical Remains
Ellesmere Island 50 MaMary Dawson of the Carnegie Museum with ~50 million year old fossil of an alligator http://www.post-gazette.com/magazine/20000319dawson1.asp
Eocene Forests in the Arctic Metasequoia stumps atAxel Heiberg Is. http://www.sas.upenn.edu/earth/arctic/data.html
Eocene Fossils from WyomingCrocodile SycamoreBorealosuchusPlatanus wyomingensis
The Arctic Then Now
The Geologic Evidence • Paleontological and Paleobotanical Remains • Marine Records • Large Geographic Coverage - 70% of Earth • Net Repository of Sediments • Continuous recorder climate change • Heat Transport and Carbon Storage
The Oxygen Isotope Recorder • Stable Isotopes of Oxygen • 16O = 99.76% • 17O = 0.04% • 18O = 0.20%
Stable Oxygen Isotopes 18O/16Osam - 18O/16Ostd 18O ‰ = ____________________________ * 1000 18O/16Ostd
Stable Oxygen Isotopes • Paleo-temperature Equation T°C = 16.9-4.2*(18OCaCO3- 18Owater )+0.1*(18OCaCO3- 18Owater )2
Stable Oxygen Isotopes Changes in 18Ocalcite 18Ocalcite = -0.23 * T°C 18Ocalcite = 18Owater
The 18Owater Effect Ice Volume ~ 1‰ for 100 m of sea level equivalent
The Hot House to Ice House Transition • Greenhouse gases • Thermohaline circulation • Continental Configurations
What caused the pCO2 to change? • High pCO2 during early Eocene could have resulted from: • Seafloor spreading changes • Large-scale volcanism
High pCO2 during early Eocene • Large-scale volcanism • Giant’s Causeway in N. Ireland • Early Tertiary age
Decreasing pCO2 after ~50 Ma • Collision began ~50 Ma • Increased weathering = Atm. CO2 decrease • CaSiO3 + CO2 = CaCO3 + SiO2
Himalayan Mountains • Broad Tibetan plateau • 3 miles above sea level
Himalayan Mountains • Indian craton collided with Eurasia
Himalayan Mountains • Miocene clastic sediments overlying Eocene limestone • Most uplift during last 15 million years
Himalayan Mountains • Indian plate subducted • Continental collision • Fold and thrust belt • Modern motion along main boundary fault
Neogene Life • Isolation of Antarctica led to glaciation • Global cooling
Drake Passage Opening33 Ma - Thermal Isolation of AntarcticaAntarctic Glaciation
The Ice Age • Glacial Maximum • Extent of continental glaciation • Six lines of evidence • Erratic boulders
The Ice Age • 2. Glacial till and basins associated with glaciation • 3. Depression of the land • Hudson Bay
The Ice Age • Glacial scouring • Lower parts of mountains of northeast U.S. are smooth • Tops were not scraped by ice sheets
The Ice Age • Lowering of sea level • Exposed continental shelves
The Ice Age • Migration of species • Mammals crossed Bering Strait on land corridors • Vegetation changed in response to global changes
The Ice Age • Pollen • Reconstruct vegetation changes • European changes
The Ice Age • Chronology of glaciation • Oxygen isotope ratios of foraminiferan skeletons in sediments • Oceans are enriched in 18O during glaciations • Northern Hemisphere glaciation began ~3M years ago • Full Ice Age 2.5 M years ago
Regional Events–Caribbean • Caribbean plate isolated
The Ice Age • Ocean circulation changed during glaciation • Glacier in NJ • Tundra in Washington, D.C.
The Ice Age • Why did the glaciation start? • Isthmus of Panama • Emplaced 3.5–3 M years ago • Started modern circulation • Gulf stream carries salty Atlantic north • Cools, sinks • Oceanic conveyor belt • High latitudes cool