Presentation on theme: "Chapter 19 The Neogene World. Guiding Questions How did marine life of Neogene time differ from that of Paelogene time? What happened to grasses and grasslands."— Presentation transcript:
Guiding Questions How did marine life of Neogene time differ from that of Paelogene time? What happened to grasses and grasslands early in Neogene time? Why might we label the Miocene Epoch the Age of the Apes? Why did global climates change during the Pliocene Epoch? What tectonic events elevated mountains in the American West in Neogene time?
Neogene Life Marine life –Miocene ancestral whales Sperm whale Baleen whales Dolphin –Miocene recovery of planktonic foraminifera
Neogene Life Terrestrial Life –Grasses –Herbs and weeds –Requires arid climate Cooler climate linked to Antarctic glaciation
Neogene Life Isolation of Antarctica led to glaciation –Global cooling
Neogene Life Mammals –Groups of large mammals –Many adapted to open terrain Even-toed ungulates –Bovidae Elephants Carnivorous mammals –New world primates
Neogene Life Spread of C 4 grasses –C 4 plants Incorporate more carbon 13 than C 3 grasses Five times more silica –Wears down teeth of grazers
Neogene Life Why the spread of C 4 grasses? –Global climate change Aridity, not CO 2, drop Alkenones indicate CO 2 rise
The Ice Age Glacial Maximum –Extent of continental glaciation Six lines of evidence Erratic boulders
The Ice Age Glacial till and basins associated with glaciation 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 18 O during glaciations Northern Hemisphere glaciation began ~3M years ago –Full Ice Age 2.5 M years ago
The Ice Age Ocean circulation changed during glaciation –Glacier in NJ –Tundra in Washington, D.C.
The Ice Age Great lakes –Last glacial maximum 35,000-10,000 years ago Wisconsin Stage –Remained when ice sheets melted back
The Ice Age Climate impacts were felt globally –Steepened temperature gradients –Increased aridity –Exception: Great Basin Unusual Lakes Great Salt Lake
The Ice Age Climate impacts were felt globally –Sahara expanded –Rain forests restricted Isolated gorilla species
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
The Ice Age Obliquity cycles –Changes in Earth’s orbit are linked to glacial oscillations –41,000-year period initially When tilt cycle is farthest from vertical, high latitudes are coolest –Period changed to 100,000 years as glacial oscillation became less frequent –Precession Cycle: 20,000- year period
Regional Events-Western Uplift and igneous activity formed western provinces –Rockies –Block-fault valleys Basin and Range –Columbia River Plateau and Snake River Plain
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