پلیستوسن
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معنی کلمه پلیستوسن
معنی واژه پلیستوسن
Pleistocene
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پلیستوسن
معنی:
پلیستوسن (Pleistocene) یکی از دورهای زمین‌شناسی است که از ۱٫۸ میلیون سال پیش تا ۱۰ هزار سال پیش را پوشش می‌دهد.
انقراض گروه بزرگی از پستانداران و شمار زیادی از گونه‌های پرندگان از اواخر دوره پلیستوسن (حدود ۱۰۰۰۰ سال پیش) آغاز شد و تا دور هولوسین ادامه یافت که شاید دلیل آن پایان عصر یخبندان بوده‌است. ماموت، ماستودون، ببر خنجردندان، تنبل زمینی، گلیپتودون، گوزن ایرلندی و خرس غارنشین از جمله حیوانات منقرض شده در اواخر پلیستوسن بودند.
نخستین انسان تکامل یافته (هوموساپینس)، در پلیستوسن پدید آمد.
منابع
در ویکی‌انبار پرونده‌هایی دربارهٔ پلیستوسن موجود است.
Turner, C. (ed.), ۱۹۹۶. The early Middle Pleistocene in Europe. Balkema (Rotterdam/Brookfield), ۳۲۹ pp. ISBN 90-5410-600-X
↑ Wall, J.D. and Przeworski, M. (2000) "When did the human population start increasing?" Genetics 155: pp. 1865–1874
ن • ب • و
زمان‌بندی زمین‌شناسی
ابردوران هادئن*
ابردوران نخست‌زیستی
ابردوران پیشین‌زیستی
ابردوران پیرازیستی
از سوی آی.سی.اس به رسمیت شناخته نشده.
این یک نوشتار خُرد زیست‌شناسی است. با گسترش آن به ویکی‌پدیا کمک کنید.
رده‌ها: پلیستوسن دوران‌های زمین‌شناسی نو زیستی
قس عربی
البلیستوسین (بالإنجلیزیة: Pleistocene) وهی فترة زمنیة امتدت من 2,588,000 إلى 11,700 سنة (ق.ح) التی تغطی فترات جلیدیة متکررة. وقد أشتق أسم البلیستوسین من الکلمتین الیونانیتین (πλεῖστος - بلیستو) وتعنی "معظم" + (καινός - کینوس) وتعنی "جدید".
تتبع فترة البلیستوسین فترة البلیوسین، ویلیها فترة الهولوسین. والبلیستوسین أول فترة من فترات العصر الرباعی أو الفترة السادسة من حقبة السینوزی. تتوافق نهایة البلیستوسین مع نهایة العصر الجلیدی الأخیر (en). کما أنه یتوافق مع نهایة العصر الحجری القدیم.
^ Gibbard, P. and van Kolfschoten, T. (2004) "The Pleistocene and Holocene Epochs" Chapter 22 بی دی إف (2.96 MiB) In Gradstein, F. M., Ogg, James G., and Smith, A. Gilbert (eds.), A Geologic Time Scale 2004 Cambridge University Press, Cambridge, ISBN 0-521-78142-6
تصنیفات: بلستوسینالحقبة الحدیثةالرباعی
قس ترکی استانبولی
Buzul Çağı ya da Pleistosen, Dördüncü Çağın yeryüzündeki toprakların %30undan fazlasının buzlarla kaplandığı bir dönemidir ve Pliyosen Çağ ile Holosen Çağ arasında yer almaktadır
Etimoloji
Yunanca "eski" anlamına gelen pleistos ve "yeni" anlamındaki kainos kelimelerinin birleştirilmesinden oluşmuştur.
Jeoloji ile ile ilgili bu madde bir taslaktır. Maddenin içeriğini geliştirerek Vikipediye katkıda bulunabilirsiniz.
g • t • dBuzul Çağlar
Kuvaterner döneminde glasiyasyon
Bugünkü glasiyasyon
Antarktika • Grönland
Pleistosen çağında glasiyasyon
Birinci • İkinci • Üçüncü–Beşinci • Yedinci
Kuvaterner öncesi glasiyasyon
Huroniyen • Kriyojeniyen • And-Sahra • Karoo
Glasiyasyon zaman çizelgesi
[[ca:huseyin
Kategoriler: Jeoloji taslaklarıBuzul Çağı
قس انگلیسی
The Pleistocene ( /ˈplaɪstəsiːn/) (symbol PS) is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the worlds recent period of repeated glaciations. The name Pleistocene is derived from the Greek πλεῖστος (pleistos "most") and καινός (kainos "new").
Sir Charles Lyell introduced this term 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.
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 sixth 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.
Contents
Dating
The Pleistocene has been dated from 2.588 million (±5,000) to 12,000 years before present (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 (11,590 calendar years BP).
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 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 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 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. 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.
Paleogeography and climate
The maximum extent of glacial ice in the north polar area during the Pleistocene period.
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 Pleistocenes 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.
Glacial features
Pleistocene climate was marked by repeated glacial cycles where continental glaciers pushed to the 40th parallel in some places. It is estimated that, at maximum glacial extent, 30% of the Earths 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 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 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 Great Britain; 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 totally covered by Lake Agassiz. Over a hundred basins, now dry or nearly so, were overflowing in 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 decrease in oceanic and other evaporation.
Major events
Further information: Timeline of glaciation
Ice ages as reflected in atmospheric CO2, stored in bubbles from glacial ice of Antarctica.
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.
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 favor of numeric data because many of the correlations were found to be either inexact or incorrect and more than four major glacials have been recognized since the historical terminology was established.
Historical names of the "four major" glacials in four regions.
Region Glacial 1 Glacial 2 Glacial 3 Glacial 4
Alps Günz Mindel Riss Würm
North Europe Eburonian Elsterian Saalian Weichselian
British Isles Beestonian Anglian Wolstonian Devensian
Midwest U.S. Nebraskan Kansan Illinoian Wisconsinan
Historical names of interglacials.
Region Interglacial 1 Interglacial 2 Interglacial 3
Alps Günz-Mindel Mindel-Riss Riss-Würm
North Europe Waalian Holsteinian Eemian
British Isles Cromerian Hoxnian Ipswichian
Midwest U.S. Aftonian Yarmouthian Sangamonian
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 "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 strategraphically defined.
Palaeocycles
The sum of transient factors acting at the Earths 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.
Milankovitch cycles
Main article: Milankovitch 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 Milankovitch cycles. These are periodic variations in regional and planetary solar radiation reaching the Earth caused by several repeating changes in the Earths 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. 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. The timing of our present interglacial interval (known as the Holocene, Postglacial, or the Present Interglacial) to that of the previous interglacial, beginning about 130,000 years ago (The Eemian Interglacial), suggests that the next glacial would likely begin in about 3,000 years.
Oxygen isotope ratio cycles
Main article: Oxygen isotope ratio cycle
In oxygen isotope ratio analysis, variations in the ratio of 18O to 16O (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 18O, 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 18O than sea water, the snow that fell on the glacier year by year nevertheless contained 18O and 16O 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 todays 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
See also: New World Pleistocene extinctions
Both marine and continental faunas were essentially modern and many animals, specifically, mammals were much larger than their modern relatives .
Pleistocene of Northern Spain showing woolly mammoth, cave lions eating a reindeer, tarpans, and woolly rhinoceros.
Pleistocene of South America showing Megatherium and two Glyptodon.
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.
The extinctions were especially severe in North America where native horses and camels were eliminated.
Asian land mammal ages (ALMA) include Zhoukoudianian, Nihewanian, and Yushean.
European land mammal ages (ELMA) include Gelasian (2.5—1.8 Ma).
North American land mammal ages (NALMA) 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.
South American 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 extends significantly back into the Pliocene.
Humans during the Pleistocene
Main articles: Human evolution, Paleolithic, and Models of migration to the New World
Scientific evidence indicates that humans evolved into their present form during the Pleistocene. In the beginning of the Pleistocene Paranthropus species are still present, as well as early human ancestors, but during the lower Palaeolithic they disappeared, and the only hominid species found in fossilic records is Homo erectus for much of the Pleistocene. The Middle and late Palaeolithic saw the appearance of new types of humans, as well as the development of more elaborate tools than found in previous eras. 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 the late Pleistocene, incorporating archaic human genetic material into the modern human gene pool.
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 California coast, Pleistocene marine deposits may be found at elevations of several hundred meters.
See also
Abbassia Pluvial
Geologic time scale
Glacial history of Minnesota
Ice age
List of fossil sites (with link directory)
Mousterian Pluvial
Paleontological Museum in Tocuila
Pleistocene megafauna
Pleistocene Park
Terasecond and longer
References
^ "Geologic Age Symbol Font (StratagemAge)". USGS. 99-430. Retrieved 2011-06-22.
^ Gibbard, P. and van Kolfschoten, T. (2004) "The Pleistocene and Holocene Epochs" Chapter 22PDF (3.1 MB) In Gradstein, F. M., Ogg, James G., and Smith, A. Gilbert (eds.), A Geologic Time Scale 2004 Cambridge University Press, Cambridge, ISBN 0-521-78142-6
^ For the top of the series, see: Lourens, L., Hilgen, F., Shackleton, N.J., Laskar, J., Wilson, D., (2004) "The Neogene Period". In: Gradstein, F., Ogg, J., Smith, A.G. (Eds.), A Geologic Time Scale 2004. Cambridge: Cambridge University Press.
^ Riccardi, Alberto C. (30 June 2009) "IUGS ratified ICS Recommendation on redefinition of Pleistocene and formal definition of base of Quaternary" International Union of Geological Sciences
^ Svensson, A., S. W. Nielsen, S. Kipfstuhl, S. J. Johnsen, J. P. Steffensen, M. Bigler, U. Ruth, and R. Röthlisberger (2005) "Visual stratigraphy of the North Greenland Ice Core Project (NorthGRIP) ice core during the last glacial period" Journal of Geophysical Research 110: (D02108)
^ Gradstein, Felix M.; Ogg, James G. and Smith, A. Gilbert (eds.) (2005) A Geologic Time Scale 2004 Cambridge University Press, Cambridge, UK, p. 28, ISBN 0-521-78142-6
^ Rio, D.; Sprovieri, R.; Castradori, D. and Di Stefano, E. (1998) "The Gelasian Stage (Upper Pliocene): a new unit of the global standard chronostratigraphic scale" Episodes 21: pp. 82-87
^ National Geographic Channel, Six Degrees Could Change The World, Mark Lynas interview. Retrieved February 14, 2008.
^ a b Richmond, G.M. and D.S. Fullerton, 1986, Summation of Quaternary glaciations in the United States of America. Quaternary Science Reviews. vol. 5, pp. 183-196.
^ Roy, M., P.U. Clark, R.W. Barendregt, J.R., Glasmann, and R.J. Enkin, 2004, Glacial stratigraphy and paleomagnetism of late Cenozoic deposits of the north-central United States, PDF version, 1.2 MB. Geological Society of America Bulletin.116(1-2): pp. 30-41; doi:10.1130/B25325.1
^ Aber, J.S. (1991) "Glaciations of Kansas" Boreas 20(4): pp. 297-314 - (contains a summary of how and why the Nebraskan, Aftonian, Kansan, and Yarmouthian stages were abandoned by modern stratigraphers).
^ Rogers, A.R. and Jorde, L.B. (1995) "Genetic evidence on modern human origins" Human Biology 67: pp. 1–36
^ Wall, J.D. and Przeworski, M. (2000) "When did the human population start increasing?" Genetics 155: pp. 1865–1874
^ Cann, R.L.; Stoneking, M. and Wilson, A.C.(1987) "Mitochondrial DNA and human evolution" Nature 325: pp. 31–36
^ Stringer, C.B. (1992) "Evolution of early modern humans" In: Jones, Steve; Martin, R. and Pilbeam, David R. (eds.) (1992) The Cambridge encyclopedia of human evolution Cambridge University Press, Cambridge, ISBN 0-521-32370-3, pp. 241–251.
^ Templeton, A. (2002) "Out of Africa again and again" Nature 416: p. 45
^ Eswarana, Vinayak; Harpendingb, Henry and Rogers, Alan R. (2005) "Genomics refutes an exclusively African origin of humans" Journal of Human Evolution 49(1): pp. 1–18 Abstract
Ogg, Jim; June, 2004, Overview of Global Boundary Stratotype Sections and Points (GSSPs, Stratigraphy.org, Accessed April 30, 2006.
External links
Wikimedia Commons has media related to: Pleistocene
The SMU-in-Taos Research Publications digital collection of anthropological and archaeological monographs contains Late Pleistocene environments of the southern high plains.
Pliocene-Pleistocene boundary at Vrica, Italy (Map)
Pleistocene Microfossils: 50+ images of Foraminifera
"Pleistocene Epoch." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica, 2011. Web. 21 Aug. 2011. -
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Categories: PleistoceneQuaternaryCenozoic
Pleistocene, polystocon
العصر الحديث الأقرب، بلستوسيني ذو علا قة بالعصر الحديث، بليستوسين
عهد چهارم زمین شناسی
انقراض گروه بزرگی از پستانداران و شمار زیادی از گونه‌های پرندگان از اواخر دوره پلیستوسن (حدود ۱۰۰۰۰ سال پیش) آغاز شد و تا دور هولوسین ادامه یافت که شاید دلیل آن پایان عصر یخبندان بوده‌است. ماموت، ماستودون، ببر خنجردندان، تنبل زمینی، گلیپتودون، گوزن ایرلندی و خرس غارنشین از جمله حیوانات منقرض شده در اواخر پلیستوسن بودند.
نخستین انسان تکامل یافته (هوموساپینس)، در پلیستوسن پدید آمد.
منابع
در ویکی‌انبار پرونده‌هایی دربارهٔ پلیستوسن موجود است.
Turner, C. (ed.), ۱۹۹۶. The early Middle Pleistocene in Europe. Balkema (Rotterdam/Brookfield), ۳۲۹ pp. ISBN 90-5410-600-X
↑ Wall, J.D. and Przeworski, M. (2000) "When did the human population start increasing?" Genetics 155: pp. 1865–1874
ن • ب • و
زمان‌بندی زمین‌شناسی
ابردوران هادئن*
ابردوران نخست‌زیستی
ابردوران پیشین‌زیستی
ابردوران پیرازیستی
از سوی آی.سی.اس به رسمیت شناخته نشده.
این یک نوشتار خُرد زیست‌شناسی است. با گسترش آن به ویکی‌پدیا کمک کنید.
رده‌ها: پلیستوسن دوران‌های زمین‌شناسی نو زیستی
قس عربی
البلیستوسین (بالإنجلیزیة: Pleistocene) وهی فترة زمنیة امتدت من 2,588,000 إلى 11,700 سنة (ق.ح) التی تغطی فترات جلیدیة متکررة. وقد أشتق أسم البلیستوسین من الکلمتین الیونانیتین (πλεῖστος - بلیستو) وتعنی "معظم" + (καινός - کینوس) وتعنی "جدید".
تتبع فترة البلیستوسین فترة البلیوسین، ویلیها فترة الهولوسین. والبلیستوسین أول فترة من فترات العصر الرباعی أو الفترة السادسة من حقبة السینوزی. تتوافق نهایة البلیستوسین مع نهایة العصر الجلیدی الأخیر (en). کما أنه یتوافق مع نهایة العصر الحجری القدیم.
^ Gibbard, P. and van Kolfschoten, T. (2004) "The Pleistocene and Holocene Epochs" Chapter 22 بی دی إف (2.96 MiB) In Gradstein, F. M., Ogg, James G., and Smith, A. Gilbert (eds.), A Geologic Time Scale 2004 Cambridge University Press, Cambridge, ISBN 0-521-78142-6
تصنیفات: بلستوسینالحقبة الحدیثةالرباعی
قس ترکی استانبولی
Buzul Çağı ya da Pleistosen, Dördüncü Çağın yeryüzündeki toprakların %30undan fazlasının buzlarla kaplandığı bir dönemidir ve Pliyosen Çağ ile Holosen Çağ arasında yer almaktadır
Etimoloji
Yunanca "eski" anlamına gelen pleistos ve "yeni" anlamındaki kainos kelimelerinin birleştirilmesinden oluşmuştur.
Jeoloji ile ile ilgili bu madde bir taslaktır. Maddenin içeriğini geliştirerek Vikipediye katkıda bulunabilirsiniz.
g • t • dBuzul Çağlar
Kuvaterner döneminde glasiyasyon
Bugünkü glasiyasyon
Antarktika • Grönland
Pleistosen çağında glasiyasyon
Birinci • İkinci • Üçüncü–Beşinci • Yedinci
Kuvaterner öncesi glasiyasyon
Huroniyen • Kriyojeniyen • And-Sahra • Karoo
Glasiyasyon zaman çizelgesi
[[ca:huseyin
Kategoriler: Jeoloji taslaklarıBuzul Çağı
قس انگلیسی
The Pleistocene ( /ˈplaɪstəsiːn/) (symbol PS) is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the worlds recent period of repeated glaciations. The name Pleistocene is derived from the Greek πλεῖστος (pleistos "most") and καινός (kainos "new").
Sir Charles Lyell introduced this term 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.
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 sixth 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.
Contents
Dating
The Pleistocene has been dated from 2.588 million (±5,000) to 12,000 years before present (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 (11,590 calendar years BP).
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 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 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 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. 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.
Paleogeography and climate
The maximum extent of glacial ice in the north polar area during the Pleistocene period.
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 Pleistocenes 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.
Glacial features
Pleistocene climate was marked by repeated glacial cycles where continental glaciers pushed to the 40th parallel in some places. It is estimated that, at maximum glacial extent, 30% of the Earths 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 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 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 Great Britain; 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 totally covered by Lake Agassiz. Over a hundred basins, now dry or nearly so, were overflowing in 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 decrease in oceanic and other evaporation.
Major events
Further information: Timeline of glaciation
Ice ages as reflected in atmospheric CO2, stored in bubbles from glacial ice of Antarctica.
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.
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 favor of numeric data because many of the correlations were found to be either inexact or incorrect and more than four major glacials have been recognized since the historical terminology was established.
Historical names of the "four major" glacials in four regions.
Region Glacial 1 Glacial 2 Glacial 3 Glacial 4
Alps Günz Mindel Riss Würm
North Europe Eburonian Elsterian Saalian Weichselian
British Isles Beestonian Anglian Wolstonian Devensian
Midwest U.S. Nebraskan Kansan Illinoian Wisconsinan
Historical names of interglacials.
Region Interglacial 1 Interglacial 2 Interglacial 3
Alps Günz-Mindel Mindel-Riss Riss-Würm
North Europe Waalian Holsteinian Eemian
British Isles Cromerian Hoxnian Ipswichian
Midwest U.S. Aftonian Yarmouthian Sangamonian
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 "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 strategraphically defined.
Palaeocycles
The sum of transient factors acting at the Earths 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.
Milankovitch cycles
Main article: Milankovitch 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 Milankovitch cycles. These are periodic variations in regional and planetary solar radiation reaching the Earth caused by several repeating changes in the Earths 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. 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. The timing of our present interglacial interval (known as the Holocene, Postglacial, or the Present Interglacial) to that of the previous interglacial, beginning about 130,000 years ago (The Eemian Interglacial), suggests that the next glacial would likely begin in about 3,000 years.
Oxygen isotope ratio cycles
Main article: Oxygen isotope ratio cycle
In oxygen isotope ratio analysis, variations in the ratio of 18O to 16O (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 18O, 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 18O than sea water, the snow that fell on the glacier year by year nevertheless contained 18O and 16O 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 todays 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
See also: New World Pleistocene extinctions
Both marine and continental faunas were essentially modern and many animals, specifically, mammals were much larger than their modern relatives .
Pleistocene of Northern Spain showing woolly mammoth, cave lions eating a reindeer, tarpans, and woolly rhinoceros.
Pleistocene of South America showing Megatherium and two Glyptodon.
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.
The extinctions were especially severe in North America where native horses and camels were eliminated.
Asian land mammal ages (ALMA) include Zhoukoudianian, Nihewanian, and Yushean.
European land mammal ages (ELMA) include Gelasian (2.5—1.8 Ma).
North American land mammal ages (NALMA) 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.
South American 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 extends significantly back into the Pliocene.
Humans during the Pleistocene
Main articles: Human evolution, Paleolithic, and Models of migration to the New World
Scientific evidence indicates that humans evolved into their present form during the Pleistocene. In the beginning of the Pleistocene Paranthropus species are still present, as well as early human ancestors, but during the lower Palaeolithic they disappeared, and the only hominid species found in fossilic records is Homo erectus for much of the Pleistocene. The Middle and late Palaeolithic saw the appearance of new types of humans, as well as the development of more elaborate tools than found in previous eras. 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 the late Pleistocene, incorporating archaic human genetic material into the modern human gene pool.
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 California coast, Pleistocene marine deposits may be found at elevations of several hundred meters.
See also
Abbassia Pluvial
Geologic time scale
Glacial history of Minnesota
Ice age
List of fossil sites (with link directory)
Mousterian Pluvial
Paleontological Museum in Tocuila
Pleistocene megafauna
Pleistocene Park
Terasecond and longer
References
^ "Geologic Age Symbol Font (StratagemAge)". USGS. 99-430. Retrieved 2011-06-22.
^ Gibbard, P. and van Kolfschoten, T. (2004) "The Pleistocene and Holocene Epochs" Chapter 22PDF (3.1 MB) In Gradstein, F. M., Ogg, James G., and Smith, A. Gilbert (eds.), A Geologic Time Scale 2004 Cambridge University Press, Cambridge, ISBN 0-521-78142-6
^ For the top of the series, see: Lourens, L., Hilgen, F., Shackleton, N.J., Laskar, J., Wilson, D., (2004) "The Neogene Period". In: Gradstein, F., Ogg, J., Smith, A.G. (Eds.), A Geologic Time Scale 2004. Cambridge: Cambridge University Press.
^ Riccardi, Alberto C. (30 June 2009) "IUGS ratified ICS Recommendation on redefinition of Pleistocene and formal definition of base of Quaternary" International Union of Geological Sciences
^ Svensson, A., S. W. Nielsen, S. Kipfstuhl, S. J. Johnsen, J. P. Steffensen, M. Bigler, U. Ruth, and R. Röthlisberger (2005) "Visual stratigraphy of the North Greenland Ice Core Project (NorthGRIP) ice core during the last glacial period" Journal of Geophysical Research 110: (D02108)
^ Gradstein, Felix M.; Ogg, James G. and Smith, A. Gilbert (eds.) (2005) A Geologic Time Scale 2004 Cambridge University Press, Cambridge, UK, p. 28, ISBN 0-521-78142-6
^ Rio, D.; Sprovieri, R.; Castradori, D. and Di Stefano, E. (1998) "The Gelasian Stage (Upper Pliocene): a new unit of the global standard chronostratigraphic scale" Episodes 21: pp. 82-87
^ National Geographic Channel, Six Degrees Could Change The World, Mark Lynas interview. Retrieved February 14, 2008.
^ a b Richmond, G.M. and D.S. Fullerton, 1986, Summation of Quaternary glaciations in the United States of America. Quaternary Science Reviews. vol. 5, pp. 183-196.
^ Roy, M., P.U. Clark, R.W. Barendregt, J.R., Glasmann, and R.J. Enkin, 2004, Glacial stratigraphy and paleomagnetism of late Cenozoic deposits of the north-central United States, PDF version, 1.2 MB. Geological Society of America Bulletin.116(1-2): pp. 30-41; doi:10.1130/B25325.1
^ Aber, J.S. (1991) "Glaciations of Kansas" Boreas 20(4): pp. 297-314 - (contains a summary of how and why the Nebraskan, Aftonian, Kansan, and Yarmouthian stages were abandoned by modern stratigraphers).
^ Rogers, A.R. and Jorde, L.B. (1995) "Genetic evidence on modern human origins" Human Biology 67: pp. 1–36
^ Wall, J.D. and Przeworski, M. (2000) "When did the human population start increasing?" Genetics 155: pp. 1865–1874
^ Cann, R.L.; Stoneking, M. and Wilson, A.C.(1987) "Mitochondrial DNA and human evolution" Nature 325: pp. 31–36
^ Stringer, C.B. (1992) "Evolution of early modern humans" In: Jones, Steve; Martin, R. and Pilbeam, David R. (eds.) (1992) The Cambridge encyclopedia of human evolution Cambridge University Press, Cambridge, ISBN 0-521-32370-3, pp. 241–251.
^ Templeton, A. (2002) "Out of Africa again and again" Nature 416: p. 45
^ Eswarana, Vinayak; Harpendingb, Henry and Rogers, Alan R. (2005) "Genomics refutes an exclusively African origin of humans" Journal of Human Evolution 49(1): pp. 1–18 Abstract
Ogg, Jim; June, 2004, Overview of Global Boundary Stratotype Sections and Points (GSSPs, Stratigraphy.org, Accessed April 30, 2006.
External links
Wikimedia Commons has media related to: Pleistocene
The SMU-in-Taos Research Publications digital collection of anthropological and archaeological monographs contains Late Pleistocene environments of the southern high plains.
Pliocene-Pleistocene boundary at Vrica, Italy (Map)
Pleistocene Microfossils: 50+ images of Foraminifera
"Pleistocene Epoch." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica, 2011. Web. 21 Aug. 2011. -
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Categories: PleistoceneQuaternaryCenozoic
Pleistocene, polystocon
العصر الحديث الأقرب، بلستوسيني ذو علا قة بالعصر الحديث، بليستوسين
عهد چهارم زمین شناسی
نمایش تصویر
اطلاعات بیشتر واژه
آواشناسی:
منبع:
واژه‌نامه آزاد
معادل ابجد:
618
شمارگان هجا:
دیگر زبان ها
انگلیسی
Pleistocene | polystocon
عربی
العصر الحديث الأقرب | بلستوسيني ذو علا قة بالعصر الحديث , بليستوسين
تشریح نگارش (هوش مصنوعی)
کلمه "پلیستوسن" به شهریاری (یا نام یک دوره زمین‌شناسی) اشاره دارد و معمولاً به شکل زیر نوشته می‌شود:
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حروف و املای صحیح: "پلیستوسن" به درستی با حرف "پ" آغاز شده و از حروف "ل"، "ی"، "س"، "ت"، "و"، "س" و "ن" تشکیل شده است. املای آن بر اساس قواعد فارسی صحیح است.
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نوشتن با حروف فارسی: این واژه باید با حروف فارسی نوشته شود و نباید از حروف لاتین یا زبان‌های دیگر در نگارش آن استفاده کرد.
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استفاده در جمله: این واژه معمولاً در متون علمی و تاریخی استفاده می‌شود. به عنوان مثال: "دوره پلیستوسن یکی از دوره‌های مهم زمین‌شناسی است که به بررسی تغییرات آب و هوایی و رویدادهای انقراض پرداخته می‌شود."
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علامت‌گذاری: هنگام استفاده از این کلمه در جملات، رعایت نکات نگارشی دیگر مانند نقطه‌گذاری و استفاده از ویرگول در صورت لزوم بسیار مهم است.
- زبان رسمی: این کلمه به زبان رسمی و در متون علمی به کار می‌رود و باید در فضای مناسب و با رعایت ادب علمی استفاده شود.
با رعایت این نکات، میتوانید این واژه را به درستی در نوشتار خود به کار ببرید.
واژگان مرتبط: عهد چهارم زمین شناسی