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