The Pleistocene Epoch follows the Pliocene Epoch and is followed by the Holocene Epoch. The Pleistocene is the first epoch of the Quaternary Period or 6th epoch of the Cenozoic Era. The end of the Pleistocene corresponds with the end of the last glacial period. It also corresponds with the end of the Paleolithic age used in archaeology.
In the ICS timescale, the Pleistocene is divided into four stages or ages, the Gelasian, Calabrian, Ionian and Tarantian. All of these stages were defined in southern Europe. In addition to this international subdivision, various regional subdivisions are often used.
Before a change finally confirmed in 2009 by the International Union of Geological Sciences, the boundary between the Pleistocene and the preceding Pliocene was regarded as being at 1.806 not 2.588 million years BP; publications from the preceding years may use either definition of the period.
During the Pleistocene, glaciers came and went, resulting in a series of ice ages punctuated by warmer periods. There were at least 20 cycles of this advance and retreat. During the ice ages, global temperatures were 5 degrees centigrade cooler than today and it was much drier, since much of the world's water was locked up in massive ice sheets. The expansion of the deserts and the action of glaciers grinding up rocks meant that dust storms would have been a lot more common in the Pleistocene than they are now. Our species evolved during this epoch.
- Gelasian (2.588-1.806 million years ago)
- Calabrian (1.806-0.781 million years ago)
- Ionian (0.781-0.126 million years ago)
- Tarantian (0.126-0.0117 million years ago)
Paleogeography and ClimateEdit
The modern continents were essentially at their present positions during the Pleistocene, the plates upon which they sit probably having moved no more than 100 km relative to each other since the beginning of the period.
According to Mark Lynas (through collected data), the Pleistocene's overall climate could be characterized as a continuous El Niño with trade winds in the south Pacific weakening or heading east, warm air rising near Peru, warm water spreading from the west Pacific and the Indian Ocean to the east Pacific, and other El Niño markers.
FaunaEditBoth marine and continental faunas were essentially modern and many animals, specifically, mammals were much larger than their modern relatives.
The severe climatic changes during the ice age had major impacts on the fauna and flora. With each advance of the ice, large areas of the continents became totally depopulated, and plants and animals retreating southward in front of the advancing glacier faced tremendous stress. The most severe stress resulted from drastic climatic changes, reduced living space, and curtailed food supply. A major extinction event of large mammals(megafauna), which included mammoths, mastodons, saber-toothed cats, glyptodons, ground sloths, Irish elk, cave bears, and short-faced bears, began late in the Pleistocene and continued into the Holocene. Neanderthals also became extinct during this period. At the end of the last ice age, cold-blooded animals, smaller mammals like wood mice, migratory birds, and swifter animals like whitetail deer had replaced the megafauna and migrated north.
Pleistocene non-marine sediments are found primarily in fluvial deposits, lakebeds, slope and loess deposits as well as in the large amounts of material moved about by glaciers. Less common are cave deposits, travertines and volcanic deposits (lavas, ashes). Pleistocene marine deposits are found primarilyin shallow marine basins mostly (but with important exceptions) 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.