The Neogene World

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Chapter 19

• The Neogene World

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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?

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11,600 ybp 23 Million years
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Neogene Life

• Marine life
• Miocene ancestral whales
• Sperm whale
• Baleen whales
• Dolphin
• Miocene recovery of planktonic foraminifera

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Neogene Life

• Terrestrial Life
• Grasses
• Herbs and weeds
• Requires arid climate
• Cooler climate linked to Antarctic glaciation

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Neogene Life

• Isolation of Antarctica led to glaciation
• Global cooling

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Neogene Life

• Mammals
• Groups of large mammals
• Many adapted to open terrain
• Even-toed ungulates
• Bovidae
• Elephants
• Carnivorous mammals
• New world primates

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Neogene Life

• Spread of C4 grasses
• C4 plants
• Incorporate more carbon 13 than C3 grasses
• Five times more silica
• Wears down teeth of grazers

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Neogene Life

• Why the spread of C4 grasses?
• Global climate change
• Aridity, not CO2, drop
• Alkenones indicate CO2 rise

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The Ice Age

• Glacial Maximum
• Extent of continental glaciation
• Six lines of evidence
• Erratic boulders

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The Ice Age

• Glacial till and basins associated with
  glaciation
• Depression of the land
• Hudson Bay

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The Ice Age

• Glacial scouring
• Lower parts of mountains of northeast U.S. are
  smooth
• Tops were not scraped by ice sheets

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The Ice Age

• Lowering of sea level
• Exposed continental shelves

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The Ice Age

• Migration of species
• Mammals crossed Bering Strait on land corridors
• Vegetation changed in response to global changes

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The Ice Age

• Pollen
• Reconstruct vegetation changes
• European changes

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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

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The Ice Age

• Ocean circulation changed during glaciation
• Glacier in NJ
• Tundra in Washington, D.C.

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The Ice Age

• Great lakes
• Last glacial maximum
• 35,000-10,000 years ago
• Wisconsin Stage
• Remained when ice sheets melted back

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The Ice Age

• Climate impacts were felt globally
• Steepened temperature gradients
• Increased aridity
• Exception Great Basin
• Unusual
• Lakes
• Great Salt Lake

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The Ice Age

• Climate impacts were felt globally
• Sahara expanded
• Rain forests restricted
• Isolated gorilla species

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The Ice Age

• Why did the glaciation start?
• Isthmus of Panama
• Emplaced 3.53 M years ago
• Started modern circulation
• Gulf stream carries salty Atlantic north
• Cools, sinks
• Oceanic conveyor belt
• High latitudes cool

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The Ice Age

• Obliquity cycles
• Changes in Earths 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

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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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Regional Events-Western

• Rocky Mountains
• Colorado Plateau
• 1 mile above sea level
• Folded sediments
• Block faulted

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Regional Events-Western

• Basin and Range
• North and south trending block-fault valleys
• Crustal thinning

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Regional Events-Western

• Cascade volcanic belt
• Sierra Nevada

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Regional EventsWestern

• Great Valley
• Mesozoic sediments
• From eroded Sierra Nevada plutons
• Later block faulted
• Sierra Nevada mountains formed

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Regional EventsWestern

• California Coastal Range
• Accreted terranes
• Divided by faults
• San Andreas

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Regional EventsWestern

• Miocene
• Subduction in north
• Faulting and mountain building in south
• Columbia Plateau basalts
• Up to 5 km thick
• Rockies uplift
• Early Miocene

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Regional EventsWestern

• Pliocene
• Igneous arc
• Snake River Plain
• Faulting and deformation in California
• Great Basin
• Terrestrial

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Regional EventsWestern

• Why the uplift?
• San Andreas transform fault
• Crustal shearing led to extensional faulting
• Does not explain Neogene elevation of Basin and
  Range

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Regional EventsWestern

• Scablands
• Bare rock scoured by floods
• Water-carved channels
• 20,00011,000 years ago
• Bretz, 1923

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Regional Events-Western

• Scablands
• Depositional features
• Giant ripples
• 5 m tall
• 100 m apart
• Water source
• Lake Missoula

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Regional Events-Eastern

• Tectonic movement
• Salisbury embayment
• Downwarp of continental margin

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Regional Events-Eastern

• Uplift in Cenozoic Era followed by erosion
• Resistant folded rock exposed
• Rivers cut through ridges

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Regional EventsCaribbean

• Caribbean plate isolated

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North American Mammal Exchange

• Isthmus of Panama
• North and South American mammals developed
  separately
• Pliocene uplift of isthmus allowed for exchange
  of terrestrial fauna

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Himalayan Mountains

• Broad Tibetan plateau
• 3 miles above sea level

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Himalayan Mountains

• Indian craton collided with Eurasia

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Himalayan Mountains

• Miocene clastic sediments overlying Eocene
  limestone
• Most uplift during last 15 million years

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Himalayan Mountains

• Indian plate subducted
• Continental collision
• Fold and thrust belt
• Modern motion along main boundary fault

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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

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Human Evolution
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Human Evolution

• Australopithecines
• Intermediate between humans and apes
• Only slightly larger brain than chimp
• Broad pelvis

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Human Evolution

• Tracks indicate bipedal walking
• Footprints similar to modern humans

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Human Evolution

• Adapted to climbing trees
• Long curved toes and fingers

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Human Evolution

• Homo
• 2.4 M years ago
• Larger skull
• Similar thigh and pelvis bones

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Human Evolution

• Stone tools
• Oldowan culture
• Found at Olduvai Gorge

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Human Evolution

• Stone tools
• Acheulian
• Found in China in association with Java Man

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Human Evolution

• Homo erectus
• 1.6 million year old boy skeleton
• Africa
• Very similar to modern humans

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Human Evolution

• Neanderthals
• Homo heidelbergensis
• Heidelberg, Germany
• 200,000700,000 years old
• Homo antecessor

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Human Evolution

• Stone tools
• Neanderthals
• Mousterian
• More sophisticated than Homo erectus tools

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Human Evolution

• Neanderthal burial sites
• Possible religion

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Human Evolution

• Cro-Magnon culture
• European
• Cave paintings of France and Spain

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