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