Oligocene

1
Oligocene

• 34 million 23 million years ago
• By Alex Willett

2
Time Frames

• The Oligocene is divided into two time frames
• Rupelian or Early Oligocene (34 28 million
  years ago)
• Chattian or Late Oligocene (28 23 million years
  ago)

3
Theory

• The start of the Oligocene is marked by a major
  extinction
• This extinction is believed to have been related
  to an impact of a large extraterrestrial object
  in Siberia and/or near Chesapeake Bay

4
Mass Extinctions

• Early in the Oligocene the Choristodera became
  extinctpossibly due to climate changes

5
Dominant Species

• Reptiles are in abundance Ex snakes and lizards
• Common mammals included Enteledont, Hyaenodon,
  and Mesohippus
• Ocean life included the baleen and toothed
  cetaceans (whales) and Charcharinid sharks
• Pinnipeds (i.e. bear-like or otter-like mammals)
  appear near the end of the Oligocene

6
Earths Development

• Continents continue to drift to their present
  positions
• Antarctica continues to become more isolated
• Permanent icecap develops over Antarctica
  (Haines)
• Mountain building in Western North America
  continues
• European Alps develop as the African plate pushes
  north into the Eurasian plate

7
Earths Development Cont

• South America separates from Antarctica and
  drifts north toward North America
• South American drift allows the Circumpolar
  currents to flow around Antarctica that rapidly
  cool the continent

8
Climate Changes

• Climate remains relatively warm
• Global cooling gradually occurs
• Earths cooling
• eventually leads
• to the Pleistocene
• glaciations

9
Flora

• Tropical and sub-tropical forests were replaced
  by temperate deciduous woodlands
• Open plains and deserts become more common
• North America flora is dominated by subtropical
  species ex cashews, roses and lychee, beech and
  pine trees