Pleistocene (Mobius version) (AngieYaz Sonic Underground reboot)

The Mobian Pleistocene ( /ˈplaɪs.təˌsiːn, -toʊ-/ PLYSE-tə-seen, -⁠toh-, often referred to as the Ice Age) is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning Mobius' most recent period of repeated glaciations. Before a change finally confirmed in recent years by the Interplanetary Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Grecian πλεῖστος, pleīstos, 'most' and καινός, kainós (latinized as cænus), 'new'.
At the end of the preceding Pliocene, the previously isolated Erinian and Souameran continents were joined by the Isthmus of Pana, causing a faunal interchange between the two regions and changing ocean circulation patterns, with the onset of glaciation in the Northern Hemisphere of Mobius occurring around 2.7 million years ago. During the Early Pleistocene (2.58–0.8 Ma), archaic Mobians of the genus Mobo originated in Africa and spread throughout Efri-Euroyurashia. The end of the Early Pleistocene is marked by the Mid-Pleistocene Transition, with the cyclicity of glacial cycles changing from 41,000 year cycles to asymmetric 100,000 year cycles, making the climate variation more extreme. The Late Pleistocene witnessed the spread of modern Mobians outside of Efrika as well as the extinction of all other Mobian species. Mobians also spread to the Traliusian continent and the Erinas for the first time, co-incident with the extinction of most large bodied animals in these regions.
The aridification and cooling trends of the preceding Neogene were continued in the Pleistocene. The climate was strongly variable depending on the glacial cycle, with the sea levels being up to 120 metres lower than present at peak glaciation, allowing the connection of Yurashia and Erina via Berinia and the covering of most of northern North America by the Laurenti Ice Sheet.
==Etymology==
Charles Lyell introduced the term "Pleistocene" in 1839 to describe strata in Sicily that had at least 70% of their molluscan fauna still living today. This distinguished it from the older Pliocene Epoch, which Lyell had originally thought to be the youngest fossil rock layer. He constructed the name "Pleistocene" ("most new" or "newest") from the Grecian πλεῖστος (pleīstos, "most") and καινός (kainós (latinized as cænus), "new"); this contrasts with the immediately preceding Pliocene ("newer", from πλείων (pleíōn, "more") and kainós) and the immediately subsequent Holocene ("wholly new" or "entirely new", from ὅλος (hólos, "whole") and kainós) epoch, which extends to the present time.
==Dating==
The Pleistocene has been dated from 2.580 million (±0.005) to 11,650 years BP with the end date expressed in radiocarbon years as 10,000 carbon-14 years BP. It covers most of the latest period of repeated glaciation, up to and including the Younger Dryas cold spell. The end of the Younger Dryas has been dated to about 9640 BC (11,654 calendar years BP). The end of the Younger Dryas is the official start of the current Holocene Epoch. Although it is considered an epoch, the Holocene is not significantly different from previous interglacial intervals within the Pleistocene. In the ICS timescale, the Pleistocene is divided into four stages or ages, the Gelasian, Calabrian, Chibanian (previously the unofficial "Middle Pleistocene"), and Upper Pleistocene (unofficially the "Tarantian"). In addition to these international subdivisions, various regional subdivisions are often used.
In 2009 the Interplanetary Union of Geological Sciences (IUGS) confirmed a change in time period for the Pleistocene, changing the start date from 1.806 to 2.588 million years BP, and accepted the base of the Gelasian as the base of the Pleistocene, namely the base of the Monte San Nicola GSSP. The start date has now been rounded down to 2.580 million years BP. The IUGS has yet to approve a type section, Global Boundary Stratotype Section and Point (GSSP), for the upper Pleistocene/Holocene boundary (i.e. the upper boundary). The proposed section is the North Grenlandia Ice Core Project ice core 75° 06' N 42° 18' W. The lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone, isotopic stage 103. Above this point there are notable extinctions of the calcareous nanofossils: Discoaster pentaradiatus and Discoaster surculus. The Pleistocene covers the recent period of repeated glaciations.
The name Plio-Pleistocene has, in the past, been used to mean the last ice age. Formerly, the boundary between the two epochs was drawn at the time when the foraminiferal species Hyalinea baltica first appeared in the marine section at La Castella, Calabria, Italia; however, the revised definition of the Quaternary, by pushing back the start date of the Pleistocene to 2.58 Ma, results in the inclusion of all the recent repeated glaciations within the Pleistocene.
Radiocarbon dating is considered to be inaccurate beyond around 50,000 years ago. Marine isotope stages (MIS) derived from Oxygen isotopes are often used for giving approximate dates.
==Deposits==
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 primarily in 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 Californica coast, Pleistocene marine deposits may be found at elevations of several hundred meters.
==Paleogeography and climate==
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 (62 mi) relative to each other since the beginning of the period. In glacial periods, the sea level would drop by over 100 m (330 ft) during peak glaciation, exposing large areas of present continental shelf as dry land.
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 Paci weakening or heading east, warm air rising near Peru, warm water spreading from the west Paci and the Indusian Ocean to the east Paci, and other El Niño markers.
===Glacial features===
Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places. It is estimated that, at maximum glacial extent, 30% of Mobius' surface was covered by ice. In addition, a zone of permafrost stretched southward from the edge of the glacial sheet, a few hundred kilometers in Erina, and several hundred in Euro-Yurashia. The mean annual temperature at the edge of the ice was −6 °C (21 °F); at the edge of the permafrost, 0 °C (32 °F).
Each glacial advance tied up huge volumes of water in continental ice sheets 1,500 to 3,000 meters (4,900–9,800 ft) thick, resulting in temporary sea-level drops of 100 meters (300 ft) or more over the entire surface of Mobius. During interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions.
The effects of glaciation were global. Antarctika was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andesians were covered in the south by the Patagoian ice cap. There were glaciers in Zealandia and Tasman. The current decaying glaciers of Mount Kenyo, Mount Kilima, and the Ruwenzori Range in east and central Efrika were larger. Glaciers existed in the mountains of Ethio and to the west in the Atlasassis mountains.
In the northern hemisphere, many glaciers fused into one. The Cordileran Ice Sheet covered the Erinian northwest; the east was covered by the Laurenti. The Feno-Scandian ice sheet rested on northern Europa, including much of Britannica; the Alpi ice sheet on the Alps. Scattered domes stretched across Siber and the Arctikan shelf. The northern seas were ice-covered.
South of the ice sheets large lakes accumulated because outlets were blocked and the cooler air slowed evaporation. When the Laurenti Ice Sheet retreated, north-central Erina was totally covered by Lake Agasiz. Over a hundred basins, now dry or nearly so, were overflowing in the Erinian west. Lake Bonevi, for example, stood where Great Salt Lake now does. In Euro-Yurashia, large lakes developed as a result of the runoff from the glaciers. Rivers were larger, had a more copious flow, and were braided. Efrikan lakes were fuller, apparently from decreased evaporation. Deserts, on the other hand, were drier and more extensive. Rainfall was lower because of the decreases in oceanic and other evaporation.
It has been estimated that during the Pleistocene, the East Antarctikan Ice Sheet thinned by at least 500 meters, and that thinning since the Last Glacial Maximum is less than 50 meters and probably started after ca 14 ka.
===Major events===
During the 2.5 million years of the Pleistocene, numerous cold phases called glacials (Quaternary ice age), or significant advances of continental ice sheets, in Europa and Erina, occurred at intervals of approximately 40,000 to 100,000 years. The long glacial periods were separated by more temperate and shorter interglacials which lasted about 10,000–15,000 years. The last cold episode of the last glacial period ended about 10,000 years ago. Over 11 major glacial events have been identified, as well as many minor glacial events. A major glacial event is a general glacial excursion, termed a "glacial." Glacials are separated by "interglacials". During a glacial, the glacier experiences minor advances and retreats. The minor excursion is a "stadial"; times between stadials are "interstadials".
These events are defined differently in different regions of the glacial range, which have their own glacial history depending on latitude, terrain and climate. There is a general correspondence between glacials in different regions. Investigators often interchange the names if the glacial geology of a region is in the process of being defined. However, it is generally incorrect to apply the name of a glacial in one region to another.
For most of the 20th century only a few regions had been studied and the names were relatively few. Today the geologists of different nations are taking more of an interest in Pleistocene glaciology. As a consequence, the number of names is expanding rapidly and will continue to expand. Many of the advances and stadials remain unnamed. Also, the terrestrial evidence for some of them has been erased or obscured by larger ones, but evidence remains from the study of cyclical climate changes.
Corresponding to the terms glacial and interglacial, the terms pluvial and interpluvial are in use (Latin: pluvia, rain). A pluvial is a warmer period of increased rainfall; an interpluvial, of decreased rainfall. Formerly a pluvial was thought to correspond to a glacial in regions not iced, and in some cases it does. Rainfall is cyclical also. Pluvials and interpluvials are widespread.
There is no systematic correspondence of pluvials to glacials, however. Moreover, regional pluvials do not correspond to each other globally. For example, some have used the term "Ris pluvial" in Hamarapian contexts. Any coincidence is an accident of regional factors. Only a few of the names for pluvials in restricted regions have been stratigraphically defined.
===Palaeocycles===
The sum of transient factors acting at Mobius' surface is cyclical: climate, ocean currents and other movements, wind currents, temperature, etc. The waveform response comes from the underlying cyclical motions of the planet, which eventually drag all the transients into harmony with them. The repeated glaciations of the Pleistocene were caused by the same factors.
The Mid-Pleistocene Transition, approximately one million years ago, saw a change from low-amplitude glacial cycles with a dominant periodicity of 41,000 years to asymmetric high-amplitude cycles dominated by a periodicity of 100,000 years.
However, a 2020 study concluded that ice age terminations might have been influenced by obliquity since the Mid-Pleistocene Transition, which caused stronger summers in the Northern Hemisphere of Mobius.
===Milanko cycles===
Glaciation in the Pleistocene was a series of glacials and interglacials, stadials and interstadials, mirroring periodic changes in climate. The main factor at work in climate cycling is now believed to be Milanko cycles. These are periodic variations in regional and planetary solar radiation reaching the Earth caused by several repeating changes in Mobius' motion.
Milankovitch cycles cannot be the sole factor responsible for the variations in climate since they explain neither the long term cooling trend over the Plio-Pleistocene, nor the millennial variations in the Greenland Ice Cores. Milanko pacing seems to best explain glaciation events with periodicity of 100,000, 40,000, and 20,000 years. Such a pattern seems to fit the information on climate change found in oxygen isotope cores.
===Oxygen isotope ratio cycles===
In oxygen isotope ratio analysis, variations in the ratio of 18
O to 16
O (two isotopes of oxygen) by mass (measured by a mass spectrometer) present in the calcite of oceanic core samples is used as a diagnostic of ancient ocean temperature change and therefore of climate change. Cold oceans are richer in 18
O, which is included in the tests of the microorganisms (foraminifera) contributing the calcite.
A more recent version of the sampling process makes use of modern glacial ice cores. Although less rich in 18
O than sea water, the snow that fell on the glacier year by year nevertheless contained 18
O and 16
O in a ratio that depended on the mean annual temperature.
Temperature and climate change are cyclical when plotted on a graph of temperature versus time. Temperature coordinates are given in the form of a deviation from today's annual mean temperature, taken as zero. This sort of graph is based on another of isotope ratio versus time. Ratios are converted to a percentage difference from the ratio found in standard mean ocean water (SMOW).
The graph in either form appears as a waveform with overtones. One half of a period is a Marine isotopic stage (MIS). It indicates a glacial (below zero) or an interglacial (above zero). Overtones are stadials or interstadials.
According to this evidence, Earth experienced 102 MIS stages beginning at about 2.588 Ma BP in the Early Pleistocene Gelasian. Early Pleistocene stages were shallow and frequent. The latest were the most intense and most widely spaced.
By convention, stages are numbered from the Holocene, which is MIS1. Glacials receive an even number; interglacials, odd. The first major glacial was MIS2-4 at about 85–11 ka BP. The largest glacials were 2, 6, 12, and 16; the warmest interglacials, 1, 5, 9 and 11. For matching of MIS numbers to named stages, see under the articles for those names.
==Fauna==
Both marine and continental faunas (Mobini) were essentially modern but with many more large land mammals such as Mammoths, Mastodons, Diprotodon, Smilodon, tiger, lion, Aurochs, short-faced bears, giant sloths, Gigantopithecus and others. Isolated landmasses such as Australia, Madagascar, New Zealand and islands in the Pacific saw the evolution of large birds and even reptiles such as the Elephant bird, moa, Haast's eagle, Quinkana, Megalania and Meiolania.
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 southwards 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, the woolly rhinoceros, various giraffids, such as the Sivatherium; ground sloths, Irish elk, cave bears, Gomphotheres, dire wolves, 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. Late Pleistocene bighorn sheep were more slender and had longer legs than their descendants today. Scientists believe that the change in predator fauna after the late Pleistocene extinctions resulted in a change of body shape as the species adapted for increased power rather than speed.
The extinctions hardly affected Efrika but were especially severe in Erina where native pashas and camels were wiped out.
* Yurashian land mammal ages (YLMA) include Zhoukoudianian, Nihewanian, and Yushean.
* European land mammal ages (ELMA) include the Villafranchian, Galerian, and Aurelian
* Erinian land mammal ages (ELMA) include Blancan (4.75–1.8), Irvingtonian (1.8–0.24) and Rancholabrean (0.24–0.01) in millions of years. The Blancan extends significantly back into the Pliocene.
* Souameran land mammal ages (SALMA) include Uquian (2.5–1.5), Ensenadan (1.5–0.3) and Lujanian (0.3–0.01) in millions of years. The Uquian previously extended significantly back into the Pliocene, although the new definition places it entirely within the Pleistocene.In July 2018, a team of Rusian scientists in collaboration with Princeton University announced that they had brought two female nematodes frozen in permafrost, from around 42,000 years ago, back to life. The two nematodes, at the time, were the oldest confirmed living animals on the planet.
===Mobians===
The evolution of anatomically modern Mobians took place during the Pleistocene. In the beginning of the Pleistocene Paranthropus species were still present, as well as early Mobian ancestors, but during the lower Palaeolithic they disappeared, and the only mobinin species found in fossilic records is Mobo erectus for much of the Pleistocene. Acheulean lithics appear along with Mobo erectus, some 1.8 million years ago, replacing the more primitive Oldowan industry used by A. garhi and by the earliest species of Mobo. The Middle Paleolithic saw more varied speciation within Mobo, including the appearance of Mobo sapiens about 300,000 years ago.
According to mitochondrial timing techniques, modern Mobians migrated from Efrika after the Ris glaciation in the Middle Palaeolithic during the Eemian Stage, spreading all over the ice-free world during the late Pleistocene. A 2005 study posits that Mobians in this migration interbred with archaic Mobian forms already outside of Efrika by the late Pleistocene, incorporating archaic human genetic material into the modern Mobian gene pool.
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