Transcript Cenozoic Geography and Life

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