Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Oligocene
Epoch Overview
Terrestrial Life Throughout the Oligocene
Oligocene Marine Life
Shifting Continents and Climates
Skull of an entelodont
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Three-toed horse
Saber-toothed cat
Saber-toothed cat
Extinct armored lizard
Tree oyster
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Earth Processes
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Shifting Continents and Climates
Tectonic activity during the Oligocene caused great changes in ocean currents. The separation of the Shetland platform from the Faeroe platform allowed Arctic cold water to flow southward. The separation of South America from Antarctica that had begun at the end of the Eocene allowed the formation of a circumpolar current, which insulated Antarctica from warm-water currents. India continued pushing up the Himalaya Mountains, causing the first isolation of the Paratethys Ocean, which occupied central and northern Europe. In turn, this led to low-oxygen conditions at basin bottoms, reduced salinity, and marine faunas that were particular to this area. As a result, the mollusks of the Paratethyan basin began a process of very rapid evolution. At this time the African plate continued to constrict the Mediterranean basin, but it still had an eastern opening to the Indian Ocean. The Arabian peninsula and Iran pushed into Asia Minor. The Atlantic continued to widen.

The seas retreated from most coastal regions. Continental separations led to cold-water currents in the South Polar region, allowing expansion of the ice cap on Antarctica that had started to form late in the Eocene. As heavier Antarctic cold water formed, it sank and flowed slowly northward along the ocean bottoms. These changes in ocean currents affected the climate on land. Environments were dominated by more open vegetation, and herbs and grasses became more widespread in midlatitudes. Although the reasons are still unclear, by the late Oligocene, warmer climates returned to many parts of the world.


Overview | Terrestrial Life Throughout the Oligocene | Oligocene Marine Life
Shifting Continents and Climates

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