Contents:
Combines a summary of research and synthetic description of the Late Quaternary, focusing on geology and climate.
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About this book Contents Customer reviews Related titles. About this book Combines a summary of research and synthetic description of the Late Quaternary, focusing on geology and climate. Contents Acknowledgements Chapter 1.
Ocean Sediments and Ice Cores 3. Ice Age Palaeoclimates and Computer Simulations 4. Ice Age Periglacial Environments 7. National Library of Australia. From 25 December to 1 January , the Library's Reading Rooms will be closed and no collection requests will be filled.
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Advanced search Search history. 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 the Earth's surface is cyclical: 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. 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 Earth's motion.
Billingen, within the Middle Swedish endmoraine zone. Wikisource has original works on the topic: Notes and references [1] [2] [3]. Exploring Environmental Change David E. September Learn how and when to remove this template message.
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 ,, 40,, and 20, years.
Such a pattern seems to fit the information on climate change found in oxygen isotope cores. 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 MIS stages beginning at about 2. 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 largest glacials were 2, 6, 12, and 16; the warmest interglacials, 1, 5, 9 and For matching of MIS numbers to named stages, see under the articles for those names.
Both marine and continental faunas were essentially modern but with many more large land mammals such as Mammoths , Mastodons , Diprotodon , Smilodon , tiger , lion , Aurochs , Short-faced bear , giant sloths , Gigantopithecus and others. Isolated places 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 , Gomphothere , 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. The extinctions hardly affected Africa but were especially severe in North America where native horses and camels were wiped out. In July , a team of Russian scientists in collaboration with Princeton University announced that they had brought two female nematodes frozen in permafrost , from around 42, 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. Acheulean lithics appear along with Homo erectus , some 1.
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The Middle Paleolithic saw more varied speciation within Homo , including the appearance of Homo sapiens about , 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. 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. From Wikipedia, the free encyclopedia.