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Cenozoic Paleogeography • • Final Breakup of Pangaea Australia and Antarctica split – Antarctica froze – Then warmed – Then froze again • • • • • Northern polar ice cap formed which lead to multiple ice ages...how? Subduction along the West and East coasts of North America Hot spots in Yellowstone National Park caused by subduction event Formation of Mt. Everest and the Swiss Alps Bye bye Tethys Sea (African and Eurasian continent collisions) Break-up of Pangaea During the early Jurassic, Pangaea began to breakup (174 Mya) and formed Laurasia and Gondwana ( aka Gondwanaland) By the Cretaceous, Gondwana split up into what has become Africa, S. A., India, Antarctica and Australia _______________________________________ Bottom Line: The final splitting of Laurasia into N.A. And Greenland happened during the Cenozoic Era Australia and Antarctica split up As Australia and Antarctica split up, Earth’s climate started to cool because of new ocean current dynamics (distribution of energy) India and Australia began to move northward Formation of the Polar Ice Cap As Antarctica localized around the magnetic south pole cold current paths developed leading to the formation of glaciers Around the mid-Cenozoic (Pliocene Epoch) water within the Arctic Ocean began to freeze and formed the first northern polar ice cap Since then, glacial activity can be measured in the abundance or lack of sea ice extent in the north pole. This process has traditionally taken thousands of years Implications of having a North Pole Blocks warm water and air from reaching the poles May significantly impact the albedo positive or negative feedback loop Oppositely, having a continental landmass above a magnetic pole decreases the likelihood of an ice age as it blocks the development of glaciers and icebergs - + Formation of the Rocky Mountains North American tectonic activity lead to the formation of the modern day Rocky Mountains Orogenic activity during the Mesozoic moved sediment inland and filled the Rocky Mountains. This made for exceptionally well-preserved fossils Phareodus; Fossil Fish found in Wyoming Subduction on the East and West Coasts of N.A. Oceanic plates from the West began to subduct the North American plate during the latter end of the Eocene Epoch = Volcanic Activity in California and the San Andreas Fault Evidence of this may be seen in the geographic make up of the southwestern US EX. Basin and Range Province Hot Spots in Yellowstone National Park Subduction from the early and mid Cenozoic influence the geology of inland regions (hot spots) Yellowstone National Park is famous for active geologic activity Geysers, Hot Springs and extrusive rhyolitic rock with a characteristic yellow colour Morning Glory Pool Formation of the Swiss Alps and the Himalayan Mountains Movement of India into Eurasia caused intense folding (and still does to this day) Rock found atop found Mt. Everest are Ordovician marine limestones Africa moved northward into Europe and formed the Swiss Alps in much the same way The Tethys Ocean Disappearance Existed between Laurasia and Gondwana and closed up as India and Africa moved Northeast into their current positions Cenozoic Life Some species had become extinct, but some survived and evolved Whales and dolphins Grass Importance of the Pliocene ice age (Savannah creation across North America) Primates; features and characteristics Hominoids -> Hominids -> Homo Sapiens Successful Life in the Cenozoic Aquatic mammals first appeared (whales and dolphins) Evolved from land dwellers Large size, hydrodynamic bodies, thermoregulatory adaptations Charismatic megafauna (large animal species with widespread popular appeal that environmental activists used to achieve conservation goals well beyond just those species) ○ Lions, tigers, Wolves, Bald Eagle, Giant Panda Successful Life in the Cenozoic Most current groups of mammals were established by the Eocene Epoch Grass The most successful and prolific angiosperm: Primitive sod-less grass developed just as the cenozoic era began Sod organization was established by the Miocene Epoch Grass started to make use of the C4 photosynthetic pathway (photosynthesis for plants in arid regions) Sod: Grass and soil complex The Pliocene Ice Age aka Quarternary Ice Age Repeated glaciation leading up to the last glaciation event caused savannahs (grassland ecosystems) to become dry and allowed new forms of life to flourish as those adapted to the savannah ecosystem died off or adapted. 1977: Dima found in Siberia Radiometric dating estimates that Dima died 40 000 years ago Development of Primates Opposable thumbs; stereoscopic vision; non-specialized teeth (generalist eating behaviour);and a relatively high body to brain ratio separate primates from other mammals - Opposable thumbs are purposed for grabbing, carrying, tool making and ‘creative interactions’ Maxilla (jaw bone) of various hominoids -Development of the occipital lobe (back of brain used in visual processing) - Development of the cerebellum (‘little brain’ traditionally thought to play a role in motor control Hominoids -> Hominids -> Homo sapiens Hominids are characterised as bipedal (walking on two legs) Sexual selection hypothesis Significant differences between Homo neanderthalensis (extinct) and Homo sapiens Neanderthals had a flared ribcage and large gait (stride) Homo sapiens had larger brains and slender hands Neanderthals had ‘thickwalled’ bones relative to Homo sapiens The ‘Out of Africa’ Hypothesis: Human Evolution Presents that modern humans evolved in Africa ~200 000 years ago and started to migrate out ~60 000 years ago Displaced/replaced other homo species in Europe and Asia Genealogy trees based on mtDNA (mitochondrial DNA) concludes that all homo sapiens descended from Mitochondrial Eve Mitochondrial DNA in Africa is the most diverse relative to other populations Hominoids -> Hominids -> Homo sapiens