Transcript Chapter 19
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 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? 11,600 ybp 23 Million years 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 C4 grasses – C4 plants • Incorporate more carbon 13 than C3 grasses • Five times more silica – Wears down teeth of grazers Neogene Life • Why the spread of C4 grasses? – Global climate change • Aridity, not CO2, drop • Alkenones indicate CO2 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 18O 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: 20,000year 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 Regional Events-Western • Rocky Mountains – Colorado Plateau • 1 mile above sea level – Folded sediments • Block faulted Regional Events-Western • Basin and Range – North and south trending block-fault valleys • Crustal thinning Regional Events-Western • Cascade volcanic belt – Sierra Nevada Regional Events–Western • Great Valley – Mesozoic sediments – From eroded Sierra Nevada plutons – Later block faulted • Sierra Nevada mountains formed Regional Events–Western • California Coastal Range – Accreted terranes – Divided by faults • San Andreas Regional Events–Western • Miocene – Subduction in north – Faulting and mountain building in south – Columbia Plateau basalts • Up to 5 km thick – Rockies uplift • Early Miocene Regional Events–Western • Pliocene – Igneous arc – Snake River Plain – Faulting and deformation in California – Great Basin • Terrestrial Regional Events–Western • Why the uplift? – San Andreas transform fault – Crustal shearing led to extensional faulting • Does not explain Neogene elevation of Basin and Range Regional Events–Western • Scablands – Bare rock scoured by floods – Water-carved channels – 20,000–11,000 years ago – Bretz, 1923 Regional Events-Western • Scablands – Depositional features – Giant ripples • 5 m tall • 100 m apart • Water source – Lake Missoula Regional Events-Eastern • Tectonic movement – Salisbury embayment • Downwarp of continental margin Regional Events-Eastern • Uplift in Cenozoic Era followed by erosion – Resistant folded rock exposed – Rivers cut through ridges Regional Events–Caribbean • Caribbean plate isolated North American Mammal Exchange • Isthmus of Panama – North and South American mammals developed separately – Pliocene uplift of isthmus allowed for exchange of terrestrial fauna 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 Human Evolution • Miocene apes radiated in Africa and Eurasia – Most were arboreal • Earliest apes – 6-7 M year old fossil skull • Sahelanthropus • Resembles both apes and humans Human Evolution Human Evolution • Australopithecines – Intermediate between humans and apes – Only slightly larger brain than chimp – Broad pelvis Human Evolution • Tracks indicate bipedal walking • Footprints similar to modern humans Human Evolution • Adapted to climbing trees – Long curved toes and fingers Human Evolution • Homo – 2.4 M years ago – Larger skull – Similar thigh and pelvis bones Human Evolution • Stone tools – Oldowan culture • Found at Olduvai Gorge Human Evolution • Stone tools – Acheulian • Found in China in association with “Java Man” Human Evolution • Homo erectus – 1.6 million year old boy skeleton – Africa • Very similar to modern humans Human Evolution • Neanderthals – Homo heidelbergensis • Heidelberg, Germany • 200,000–700,000 years old – Homo antecessor Human Evolution • Stone tools – Neanderthals • Mousterian • More sophisticated than Homo erectus tools Human Evolution • Neanderthal burial sites – Possible religion Human Evolution • Cro-Magnon culture – European – Cave paintings of France and Spain