Oligocene Guide, Meaning , Facts, Information and Description
The
Oligocene epoch is a geologic
period of time that extends from about 33.7 million to 23.8 million years before the present (BP). 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 refers to the sparsity of additional modern
mammalian faunas 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 epoch of the
Tertiary era.
The start of the Oligocene is marked by a major extinction event that may be related to the impact of large extraterrestrial object in Siberia and/or near Chesapeake Bay. The Oligocene-Miocene boundary is not set at an easily identified worldwide event but rather at regional boundaries between the warmer Oligocene and the relatively cooler Miocene.
Oligocene faunal stages from youngest to oldest are:
- Chattian, Chickasawhayan
- Rupelian, Stampian, Tongrian, Latdorfian, Vicksburgian
During this period, the continents continued to
drift toward their present positions. Climates remained warm, although the slow global cooling that eventualty led to the
Pleistocene glaciations started around the end of the epoch.
Mountain building in western
North America continued, and the
Alps started to rise in
Europe as the
African plate continued to push north into the
Eurasian plate. A brief marine incursion marks the early Oligocene in Europe. Oligocene marine exposures are rare in North America. There appears to have been a land bridge in the early Oligocene between North America and Europe as the
faunas of the two regions are very similar. Important Oligocene land faunas are found on all continents except
Australia. Marine faunas became fairly modern, as did terrestrial
vertebrate faunas in the northern continents. This was probably more as a result of older forms dying out than as a result of more modern forms evolving.
South America was apparently isolated from the other continents and evolved a quite distinct fauna during the Oligocene.
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