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Oligocene epoch

Over 30 million years ago, the Oligocene epoch saw the start of the global cooling that would eventually shift the Earth's climate to one where glaciers were present and ice ages were possible. Worldwide, this was the time when grasslands began to expand and forests - especially tropical ones - shrank correspondingly. Animals evolved to fit the new, open landscape and many fast-running prey and predator species arose as a result.

Began: 33.7 million years ago

Ended: 23.8 million years ago

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What the Earth was like

A map of the Earth in the Oligocene Epoch

Reconstruction of the Earth in the Oligocene epoch, 33.7 million - 23.8 million years ago. Credit: Dr Ron Blakey, NAU Geology.

Causes of extinctions

During this period the following extinction level events are thought to have occurred.

Climate change Climate change
Earth's climate is not constant. Over geological time, the Earth's dominant climate has gone from ice age to tropical heat and from steamy jungles to searing deserts.

Types of fossils formed in this period

Amber
Amber Trace fossils
Trace fossils

About

The Oligocene (symbol OG ) is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present (33.9±0.1 to 23.03±0.05 Ma). As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly uncertain. The name Oligocene comes from the Greek ὀλίγος (oligos, few) and καινός (kainos, new), and refers to the sparsity of additional modern mammalian species of fauna after a burst of evolution during the Eocene. The Oligocene follows the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period.

The Oligocene is often considered an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Major changes during the Oligocene included a global expansion of grasslands, and a regression of tropical broad leaf forests to the equatorial belt.

The start of the Oligocene is marked by a notable extinction event called the Grande Coupure; it featured the replacement of European fauna with Asian fauna, except for the endemic rodent and marsupial families. By contrast, the Oligocene-Miocene boundary is not set at an easily identified worldwide event but rather at regional boundaries between the warmer late Oligocene and the relatively cooler Miocene.

Read more at Wikipedia

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Geological time

  1. Origin of the Earth 4.6 billion years ago
  2. Archean era
  3. Cryogenian period
  4. Ediacaran period
  5. Cambrian period
  6. Ordovician period
  7. Silurian period
  8. Devonian period
  9. Carboniferous period
  10. Permian period
  11. Triassic period
  12. Jurassic period
  13. Cretaceous period
  14. Palaeocene epoch
  15. Eocene epoch
  16. Oligocene epoch
  17. Miocene epoch
  18. Pliocene epoch
  19. Pleistocene epoch
  20. Holocene epoch
  21. Present day

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