System (period) | Series | Stage (age) | Lower boundary, Ma | |
---|---|---|---|---|
Quaternary | Holocene | Meghalayan | 0.0042 | |
Northgrippian | 0.0082 | |||
Greenlandian | 0.0117 | |||
Pleistocene | Upper | 0.129 | ||
Chibanian | 0.774 | |||
Calabrian | 1.80 | |||
Gelasian | 2.58 | |||
Neogene | Pliocene | Piacenzian | older | |
Subdivisions and "golden spikes" according to IUGS as of September 2023[1] |
The Pleistocene is the first epoch of the Quaternary period or 6th epoch of the Cenozoic Era. It corresponds to the Peistocene series of the Quaternary system in stratigraphy. The Pleistocene Epoch follows the Pliocene Epoch and is followed by the Holocene Epoch. It lasted from 2,58 million to 11,700 years BP that spans the world's recent period of repeated glaciations. 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. The name Pleistocene' means 'Most New'.
All human species including Homo sapiens, the last of them, evolved during this epoch.
Definition[]
The GSSP of the Gelasian, the lower stage of the Pleistocene, was ratified in 1998. However, at that time this stage was included in the Pliocene series. As the base of the entire Pleistocene series and the whole Quaternary system, the lower boundary of the Gelasian was accepted in 2009. The lower boundary is defined in Monte San Nicola, Sicily, Italy, and related to the base of marly layer overlying sapropel MPRS 250. The magnetic Matuyama/Gauss boundary lies in 1 m below the GSSP.[2]
Subdivisions[]
In the ICS timescale, the Pleistocene is divided into four stages or ages, the Gelasian, Calabrian, Chibanian and unnamed Upper. 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.
Paleogeography[]
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. Due to the vast ice masses in the polar regions, sea levels were much lower than they are now, and there was a land connection between Asia and North America, as well as between Asia and Australia. About 400,000 years ago, the last island of the Hawaiian archipelago was formed.
Climate[]
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.
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.
Fauna[]
Both 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. In the seas, the number of cartilaginous fish, which previously played a more significant role in ecosystems, has decreased. Whales and sirenians with a layer of subcutaneous fat inhabited the high-latitude seas. Ontocetus, a seal, was one of those mammals that failed to adapt to the cooling and became extinct in the Early Pleistocene. Walrus, a relative of Ontocetus with a similar feeding method, occupied its ecological niche in the northern seas.[3] 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 lions, cave bears, and short-faced bears, began late in the Pleistocene and continued into the Holocene. Researchers most often cite human hunting and climate change as the reasons for this extinction. Another factor could be an allergy to pollen from flowering plants, which spread widely northward during the warming period at the end of the epoch. Allergies caused insensitivity to odors, which made it difficult for animals to find mates, and as a result, populations gradually declined.[4] Most human species including Neanderthals also became extinct during this epoch. 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.
References[]
- ↑ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. https://stratigraphy.org/chart#latest-version.
- ↑ "GSSP Table - Cenozoic Era". https://timescalefoundation.org/gssp/index.php?parentid=2.
- ↑ Boisville M, Chatar N, Kohno N., New species of Ontocetus (Pinnipedia: Odobenidae) from the Lower Pleistocene of the North Atlantic shows similar feeding adaptation independent to the extant walrus (Odobenus rosmarus) PeerJ (August 13, 2024). DOI: 10.7717/peerj.17666
- ↑ Gleb Zilberstein, Svetlana Zilberstein, Pier Giorgio Righetti, Vincenzo Cunsolo, Alexei Tikhonov, Andrey Bublichenko (September 2024) "Sense of smell reduction as factor for mammoth’s and other mammals extinction. Immunoglobulins as possible markers". Earth History and Biodiversity, vol. 1. https://doi.org/10.1016/j.hisbio.2024.100008