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The Pleistocene epoch is part of the geologic timescale, usually dated as 1.8-1.6 million to 10,000 years
before present, with the end date expressed in radiocarbon years.
It covers most of the latest period of repeated glaciation, up to and including
the Younger Dryas cold period that interrupted the final deglaciation.
The end of the Younger Dryas has been dated to about 9600 BC (11550 calendar years BP).
The GSSP for the start of the Pleistocene is in a reference section at Virca in Italy
that has unresolved dating ambiguities.
The Pleistocene follows the Pliocene Epoch and is followed by the Holocene Epoch. The Pleistocene is the first of the two epochs of the Quaternary Period or 6th epoch of the
Cenozoic Era.
As with other older geologic periods, the rock beds that define the start of the Pleistocene are well identified, but the
exact dates of the start and end of the period are slightly uncertain. The Pleistocene was originally intended to cover the
recent period of repeated glaciations, however, the start was set too late and some
early cooling and glaciation are now set in the Pliocene. Some would prefer a start date of around 2.5 million years BP.
There are no Faunal stages defined for the Pleistocene or Holocene.
Continents were at essentially their modern positions during the Pleistocene probably moving no more than 100km at most. The
Pleistocene climate was characterized by repeated glacial cycles where continental glaciers pushed to the 40th parallel in
places. Four major glacial events have been identified as well as many minor intervening events. The four major identified
glacial excursions were the Nebraskan-Gunz, Kansan-Mindel, Illinoian-Riss, and Wisconsin-Wurm. There may have been as many as 14
additional unnamed advances whose results have been largely erased by the later glaciers. Each glacial advance tied up huge
volumes of water in continental ice sheets 1500-3000 meters thick resulting in temporary sea level drops of 100 meters or more.
Antarctica was ice-bound throughout the Pleistocene as well as the preceding
Pliocene Period.
Both marine and continental faunas were essentially modern. Humans evolved into modern man during the Pleistocene. Major
extinctions of large mammals including mammoths, mastodons, sabertoothed cats and giant sloths started late in the Pleistocene
and continued into the Holocene. The extinctions were especially severe in North America where native horses and camels were
eliminated.
Pleistocene continental deposits are found primarily in lakebeds and caves as well as in the large amounts of material moved
about by glaciers. Pleistocene marine deposits are found primarily in areas within a few tens of kilometers of the modern
shoreline. In a few geologically active areas such as the Southern California Coast, Pleistocene marine deposits may be found at
elevations of several hundred meters.
The end of the Pleistocene corresponds with the end of the Paleolithic age
used in archaeology.
- See also: Geologic Time Scale
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