75-710: The Atlin Volcanic Field , also called the Llangorse Volcanic Field and the Surprise Lake Volcanic Field , is a group of late- Pleistocene to Holocene cinder cones that lies on the Teslin Plateau east of Atlin Lake , Canada. The largest volcanic feature is the 1880-m-high Ruby Mountain which has been partially dissected by Pleistocene and post-Wisconsin glaciation. Two basaltic cinder cones at
150-635: 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 Greenland 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
225-585: 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 . Glaciation in the Pleistocene
300-531: A change in the use of coastal resources and advancements in marine technology. The reasons for these changes have not been confirmed; various triggering mechanisms have been theorized such as climate change , the arrival of new people, or the struggle for resources. The South American land mammal age , the Lujanian , corresponds with the late Pleistocene. The Lujanian is a geologic period from 0.8 - 0.11Ma specifically for prehistoric South American fauna. There
375-574: A deviation from today's annual mean temperature, taken as zero. This sort of graph is based on another 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
450-421: 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
525-571: A group of people were going down from the Yukon to investigate the eruption, but no further reports were apparently made. Several recent studies, including a summary by Edwards et al. (2003) published by the Geological Survey of Canada, have determined that Ruby Mountain was definitely not the site of a historic eruption, nor were the Cracker Creek or Volcanic Creek cones. One possible explanation for
600-664: A return to glacial conditions until 11.7 ka. Paleoclimatology holds that there was a sequence of stadials and interstadials from about 16 ka until the end of the Pleistocene. These were the Oldest Dryas (stadial), the Bølling oscillation (interstadial), the Older Dryas (stadial), the Allerød oscillation (interstadial) and finally the Younger Dryas. The end of the Younger Dryas marks
675-568: A team of Russian 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. The evolution of anatomically modern humans took place during the Pleistocene. At the beginning of the Pleistocene Paranthropus species were still present, as well as early human ancestors, but during
750-561: A true domestic dog have been dated to 14,200 years ago. Domestication first happened in Eurasia but could have been anywhere from Western Europe to East Asia. Domestication of other animals such as cattle, goats, pigs, and sheep did not begin until the Holocene when settled farming communities became established in the Near East. The cat was probably not domesticated before c. 7500 BC at
825-499: Is conducive for preserving fossils . Neanderthal hominins ( Homo neanderthalensis ) inhabited Eurasia until becoming extinct between 40 and 30 ka, towards the end of the Pleistocene and possibly into the early Holocene and were replaced with modern humans ( Homo sapiens ) who emerged from East Africa about 195,000 years ago. Neanderthals co-existed with the Homo sapiens until they died out. In Eurasia, extinction happened throughout
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#1732855060814900-591: Is due to the lack of chronological information. The resemblance of Late Pleistocene species in Northern Africa to modern animals is the same as in Southern Africa but it's extremely difficult to date when these fauna came into place because of the lack of reliable samples from the mid-Pleistocene. Most of the significant fossil records are from the Maghreb because of its geology which helps to create deep caves which
975-765: Is estimated that, at maximum glacial extent, 30% of the Earth's surface was covered by ice. In addition, a zone of permafrost stretched southward from the edge of the glacial sheet, a few hundred kilometres in North America , and several hundred in Eurasia . 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 metres (4,900–9,800 ft) thick, resulting in temporary sea-level drops of 100 metres (300 ft) or more over
1050-491: Is evidence of human habitation in mainland Australia , Indonesia , New Guinea and Tasmania from c. 45,000 BC. The finds include rock engravings, stone tools and evidence of cave habitation. In Australia, there are sites which show evidence of pollen records from the Late Pleistocene and they are mostly found in more temperate regions of the continent. Some megafauna decreased in size over time, while others remained
1125-827: Is known in Europe as the Würm (Alpine) or Devensian (Great Britain) or Weichselian glaciation (northern Europe); these are broadly equated with the Wisconsin glaciation (North America), though technically that began much later. The Last Glacial Maximum was reached during the later millennia of the Würm/Weichselian, estimated between 26 ka and 19 ka when deglaciation began in the Northern Hemisphere. The Würm/Weichselian endured until 16 ka with Northern Europe, including most of Great Britain , covered by an ice sheet. The glaciers reached
1200-454: Is no systematic correspondence between pluvials to glacials, however. Moreover, regional pluvials do not correspond to each other globally. For example, some have used the term "Riss pluvial" in Egyptian contexts. Any coincidence is an accident of regional factors. Only a few of the names for pluvials in restricted regions have been stratigraphically defined. The sum of transient factors acting at
1275-541: Is still heavily debated what caused the extinctions. Bison occidentalis and Bison antiquus , an extinct subspecies of the smaller present-day bison, survived the late Pleistocene period, between about 12 and 11 ka ago. Clovis people depended on these bison as their major food source. Earlier kills of camels, horses, and muskoxen found at Wally's beach were dated to 13.1–13.3 ka B.P. Over 50 genera (~ 83%) of megafauna in South and North America went extinct during
1350-638: The Alpine ice sheet on the Alps . Scattered domes stretched across Siberia and the Arctic 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 Laurentide Ice Sheet retreated, north-central North America was completely covered by Lake Agassiz . Over a hundred basins, now dry or nearly so, were overflowing in
1425-692: The Great Lakes in North America. Sea levels fell and two land bridges were temporarily in existence that had significance for human migration : Doggerland , which connected Great Britain to mainland Europe; and the Bering land bridge which joined Alaska to Siberia . The last Ice Age was followed by the Late Glacial Interstadial , a period of global warming to 12.9 ka, and the Younger Dryas ,
1500-670: The Japanese archipelago has been traced to prehistoric times between 40,000 BC and 30,000 BC. The earliest fossils are radiocarbon dated to c. 35,000 BC. An archeological record of Neanderthals has been found in Asia along with records of two other hominin populations, the Denisovans and Homo floresiensis . Japan was once linked to the Asian mainland by land bridges via Hokkaido and Sakhalin Island to
1575-525: The Nile Valley as the Sahara was transformed from grassland to desert. The Nazlet Khater skeleton was found in 1980 and has been radiocarbon dated to between 30,360 and 35,100 years ago. Most of the knowledge of the Late Pleistocene is obtained from regions like Morocco , Algeria , Tunisia , some coastal regions of Maghreb , Libya and Egypt . The only issue with interpreting the data from this region
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#17328550608141650-761: The North American land mammal age scale, the Rancholabrean spans the time from c. 240,000 years ago to c. 11,000 years ago. It is named after the Rancho La Brea fossil site in California , characterized by extinct forms of bison in association with other Pleistocene species such as the mammoth . During the Late Pleistocene about 35 genera of megafauna went extinct including species such as mastodons , saber-toothed cats and giant ground sloths . Some other species went extinct in North America but not globally. it
1725-635: The Ruwenzori Range in east and central Africa were larger. Glaciers existed in the mountains of Ethiopia and to the west in the Atlas Mountains . In the northern hemisphere, many glaciers fused into one. The Cordilleran Ice Sheet covered the North American northwest; the east was covered by the Laurentide . The Fenno-Scandian ice sheet rested on northern Europe , including much of Great Britain;
1800-437: The calcareous nannofossils : 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, Italy. However,
1875-477: 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
1950-517: The mammoth , mastodon , and Irish elk became extinct. Upper Paleolithic people also made paintings and engravings on walls. Cave paintings have been found at Lascaux in the Dordogne which may be more than 17,000 years old. These are mainly buffalo , deer , and other animals hunted by humans. Later paintings occur in caves throughout the world, including Altamira , Spain, and in India, Australia, and
2025-537: The woolly rhinoceros , various giraffids , such as the Sivatherium ; ground sloths , Irish elk , cave lions , cave bears , Gomphotheres , American lions , 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
2100-701: The "Tarantian"). In addition to these international subdivisions, various regional subdivisions are often used. In 2009 the International 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
2175-478: The Alps and interglacials (temperate phase). The evidence of the changes in climatic conditions was from fragmentary sequences in formerly glaciated areas in northern Europe . The only domesticated animal in the Pleistocene was the dog , which evolved from the grey wolf into its many modern breeds . It is believed that the grey wolf became associated with hunter-gatherer tribes around 15 Ka. The earliest remains of
2250-558: 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 and interglacials receive an odd number. 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 were 1, 5, 9 and 11. For matching of MIS numbers to named stages, see under
2325-402: The Earth's most recent period of repeated glaciations . Before a change was finally confirmed in 2009 by the International 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
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2400-409: The Earth's 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
2475-593: The Late Pleistocene. Some species which went extinct at the end of the Late Pleistocene in Southern Africa are the giant warthog , long-horn buffalo, Southern springbok , etc. These species were common because their distribution changed in response to climatic influences on vegetation. Carnivores were more widespread due to their varying habitat requirements. In Egypt , the Late (or Upper) Palaeolithic began sometime after 30,000 BC. People in North Africa had relocated to
2550-479: The North American west. Lake Bonneville , for example, stood where Great Salt Lake now does. In Eurasia, large lakes developed as a result of the runoff from the glaciers. Rivers were larger, had a more copious flow, and were braided . African 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
2625-658: The Pleistocene but those that happened during the Later Pleistocene were of megafauna and there were no replacements for the extinct species. Some Molluscan species went extinct but not on the same scale as the mammals living during the time. Some examples of species which extinct without replacements include the Straight-tusked elephant ( Palaeoloxodon antiquus ), Giant deer ( Megaloceros giganteus ), cave bear ( Ursus spelaeus ) and woolly rhinoceros ( Coelodonta antiquitatis ). Several large mammalian species including
2700-490: The Pleistocene's overall climate could be characterised 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. Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places. It
2775-733: The Pleistocene, the East Antarctic 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. 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 Europe and North America, 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
2850-411: 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 up to 120 m (390 ft) lower than today during peak glaciation, exposing large areas of the present continental shelf as dry land. According to Mark Lynas (through collected data),
2925-478: The Pleistocene. most mega mammals (>1000kg) and large mammals (>40kg) went extinct by the end of the Late Pleistocene. During this period there was a major cooling event called the Younger Dryas and the Clovis culture of capturing game became more prominent. Diverse factors such as climate change may have triggered this extinction but it's still in debate what the major factors were. The Late Pleistocene saw
3000-620: The Pleistocene. The climate was strongly variable depending on the glacial cycle, with the sea levels being up to 120 metres (390 ft) lower than present at peak glaciation, allowing the connection of Asia and North America via Beringia and the covering of most of northern North America by the Laurentide Ice Sheet . 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
3075-664: The Sahara. Magdalenian hunter-gatherers were widespread in western Europe about 20 -12.500 cal BP years ago until the end of the Pleistocene. An example of this is the antler-working done by the human groups who lived in the Santimamine cave in the Magdalenian. They invented the earliest known harpoons using reindeer horn. Climatic conditions during the Late Pleistocene in Eurasia were predominantly cold with glaciation events happening in northern Europe , northwest Siberia and
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3150-469: 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
3225-687: The appearance of Homo sapiens about 300,000 years ago. Artifacts associated with modern human behavior are unambiguously attested starting 40,000–50,000 years ago. According to mitochondrial timing techniques, modern humans migrated from Africa after the Riss 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 humans in this migration interbred with archaic human forms already outside of Africa by
3300-515: The articles for those names. Both marine and continental faunas were essentially modern but with many more large land mammals such as Mammoths , Mastodons , Diprotodons , Smilodons , tigers , lions , Aurochs , short-faced bears , giant sloths , species within Gigantopithecus and others. Isolated landmasses such as Australia , Madagascar , New Zealand and islands in the Pacific saw
3375-539: The beginning of the Last Interglacial around 130,000 years ago (corresponding with the beginning of Marine Isotope Stage 5 ). The Late Pleistocene ends with the termination of the Younger Dryas , some 11,700 years ago when the Holocene Epoch began. The term Upper Pleistocene is currently in use as a provisional or "quasi-formal" designation by the International Union of Geological Sciences (IUGS). Although
3450-464: The boundary between the Pleistocene and Holocene Epochs. Hominids in all parts of the world were still culturally and technologically in the Palaeolithic (Old Stone) Age . Tools and weapons were basic stone or wooden implements. Nomadic tribes followed moving herds. Non-nomadics acquired their food by gathering and hunting . Its present physical geography and climate have changed over time caused by
3525-527: The climate variation more extreme. The Late Pleistocene witnessed the spread of modern humans outside of Africa as well as the extinction of all other human species. Humans also spread to the Australian continent and the Americas 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
3600-662: The earliest, again in the Near East . A butchered brown bear patella found in Alice and Gwendoline Cave in County Clare and dated to 10,860 to 10,641 BC indicates the first known human activity in Ireland . The topography and geography of Asia were subject to frequent changes such as the creation of land bridges when sea levels dropped which helped with the expansion and migration of human populations . The first human habitation in
3675-529: 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 Greek πλεῖστος ( pleîstos ) 'most' and καινός ( kainós ; Latinized as cænus ) 'new'. At the end of the preceding Pliocene, the previously isolated North and South American continents were joined by the Isthmus of Panama , causing a faunal interchange between
3750-501: The entire surface of the Earth. 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. Antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andes were covered in the south by the Patagonian ice cap. There were glaciers in New Zealand and Tasmania . The current decaying glaciers of Mount Kenya , Mount Kilimanjaro , and
3825-414: The eruption found in the region and the 19th-century report is considered uncertain. Volcanoes within the field include: Pleistocene The Pleistocene ( / ˈ p l aɪ s t ə ˌ s iː n , - s t oʊ -/ PLY -stə-seen, -stoh- ; referred to colloquially as the Ice Age ) is the geological epoch that lasted from c. 2.58 million to 11,700 years ago, spanning
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#17328550608143900-672: 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 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 ,
3975-410: The extinction of all archaic human species. Paleolithic Epipalaeolithic Mesolithic Neolithic The proposed beginning of the late Pleistocene is the end of the Penultimate Glacial Period (PGP) 126 ka when the Riß glaciation (Alpine) was being succeeded by the Eemian (Riß-Würm) interglacial period . The Riß-Würm ended 115 ka with the onset of the Last Glacial Period (LGP) which
4050-414: 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
4125-409: The heads of Cracker Creek and Volcanic Creek lie within glacially dissected U-shaped valleys and may be of postglacial age. A Yukon newspaper reported in 1898 that an eruption was occurring near Atlin about 80 km (50 mi) south of Gladys Lake . Miners working in the area reportedly were able to work during the dark nights, due to the glow of the eruption. The article also reported that
4200-450: The historical terminology was established. 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 is 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
4275-552: 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 kilometres 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 metres. The modern continents were essentially at their present positions during
4350-405: The late Pleistocene, incorporating archaic human genetic material into the modern human gene pool. Late Pleistocene The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy , also known as the Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch within
4425-420: The lower Palaeolithic they disappeared, and the only hominin species found in fossilic records is Homo erectus for much of the Pleistocene. Acheulean lithics appear along with Homo erectus , some 1.8 million years ago, replacing the more primitive Oldowan industry used by A. garhi and by the earliest species of Homo . The Middle Paleolithic saw more varied speciation within Homo , including
4500-478: 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 Africa but were especially severe in North America where native horses and camels were wiped out. In July 2018,
4575-408: The movement of tectonic plates and volcanoes but glacial cycles and sea level variation have a more significant effect on the vertebrate communities during the Late Pleistocene. The Late Pleistocene was the time when most animals evolved to resemble modern-day animals and they managed to live through the Late mid-Pleistocene since there were no extinction events of megafauna until the end of
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#17328550608144650-503: The north but was unconnected at this time when the main islands of Hokkaido, Honshu , Kyushu and Shikoku were all separate entities. Human migrations happened during this time with people coming in from Eurasia . From about 28 ka, there were migrations across the Bering land bridge from Siberia to Alaska . The people became the Native Americans . It is believed that the original tribes subsequently moved down to Central and South America under pressure from later migrations. In
4725-530: 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 Greek 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
4800-408: The ongoing Quaternary Period. It is currently defined as the time between c. 129,000 and c. 11,700 years ago. The late Pleistocene equates to the proposed Tarantian Age of the geologic time scale , preceded by the officially ratified Chibanian (commonly known as the Middle Pleistocene). The beginning of the Late Pleistocene is the transition between the end of the Penultimate Glacial Period and
4875-465: The period, reaching their lowest during the Last Glacial Maximum around 26-20,000 years ago. Most of the world's large ( megafaunal ) animals became extinct during the Late Pleistocene as part of the Late Pleistocene extinctions , a trend that continued into the Holocene. In palaeoanthropology , the late Pleistocene contains the Upper Palaeolithic stage of human development, including the early human migrations of modern humans outside of Africa, and
4950-403: The present time. The Pleistocene has been dated from 2.580 million (±0.005) to 11,700 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 9700 BCE (11,700 calendar years BP). The end of
5025-417: The ratio of O to 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 O , which is included in the tests of the microorganisms ( foraminifera ) contributing the calcite. A more recent version of
5100-512: 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. Pleistocene non-marine sediments are found primarily in fluvial deposits , lakebeds, slope and loess deposits as well as in
5175-407: The sampling process makes use of modern glacial ice cores. Although less rich in O than seawater, the snow that fell on the glacier year by year nevertheless contained O and 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
5250-511: 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 known as Dansgaard-Oeschger events and Heinrich events. Milankovitch 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. In oxygen isotope ratio analysis, variations in
5325-432: The story is that placer miners found gold-bearing gravels beneath an ancient lava flow at the base of Ruby Mountain, and were actively tunneling under the old lava flow to mine the gravels. As its name suggests, Ruby Mountain is ruby-colored due to the scoriaceous tephra that covers much of its summit and the summer sun shining off of the ruby-red flanks of the volcano may have started the rumour. There have been no evidence of
5400-421: The study of cyclical climate changes. The glacials in the following tables show historical usages, are a simplification of a much more complex cycle of variation in climate and terrain, and are generally no longer used. These names have been abandoned in favour of numeric data because many of the correlations were found to be either inexact or incorrect and more than four major glacials have been recognised since
5475-543: The three oldest ages of the Pleistocene (the Gelasian , the Calabrian and the Chibanian ) have been officially defined, the late Pleistocene has yet to be formally defined. Following the brief Last Interglacial warm period (~130–115,000 years ago), where temperatures were comparable to or warmer than the Holocene, the Late Pleistocene was dominated by the cool Last Glacial Period , with temperatures gradually lowering throughout
5550-670: The two regions and changing ocean circulation patterns, with the onset of glaciation in the Northern Hemisphere occurring around 2.7 million years ago. During the Early Pleistocene (2.58–0.8 Ma), archaic humans of the genus Homo originated in Africa and spread throughout Afro-Eurasia . 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
5625-543: Was a series of glacials and interglacials, stadials and interstadials, mirroring periodic climate changes. The main factor at work in climate cycling is now believed to be Milankovitch cycles . These are periodic variations in regional and planetary solar radiation reaching the Earth caused by several repeating changes in the Earth's motion. The effects of Milankovitch cycles were enhanced by various positive feedbacks related to increases in atmospheric carbon dioxide concentrations and Earth's albedo. Milankovitch cycles cannot be
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