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The Quaternary (Template:IPAc-en Template:Respell) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the Phanerozoic eon.<ref name="ICS2013">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It follows the Neogene Period and spans from 2.58 million years ago to the present.<ref name="ICS StratChart 2022-02">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The Quaternary Period is divided into two epochs: the Pleistocene (2.58 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today); a proposed third epoch, the Anthropocene, was rejected in 2024 by IUGS, the governing body of the ICS.
The Quaternary is typically defined by the Quaternary glaciation, the cyclic growth and decay of continental ice sheets related to the Milankovitch cycles and the associated climate and environmental changes that they caused.<ref name="Denton2010">Template:Cite journal</ref><ref>Template:Cite book</ref>
Research historyEdit
Template:See also In 1759 Giovanni Arduino proposed that the geological strata of northern Italy could be divided into four successive formations or "orders" (Template:Langx).<ref>See:
- Template:Cite journal Available at: Museo Galileo (Florence (Firenze), Italy) From p. 158 (clviii): "Per quanto ho potuto sinora osservavare, la serie di questi strati, che compongono la corteccia visibile della terra, mi pare distinta in quattro ordini generali, e successivi, senza considerarvi il mare." (As far as I have been able to observe, the series of these layers that compose the visible crust of the earth seems to me distinct in four general orders, and successive, not considering the sea.)
- English translation: Template:Cite journal</ref> The term "quaternary" was introduced by Jules Desnoyers in 1829 for sediments of France's Seine Basin that clearly seemed to be younger than Tertiary Period rocks.<ref>Template:Cite journal From p. 193: "Ce que je désirerais … dont il faut également les distinguer." (What I would desire to prove above all is that the series of tertiary deposits continued – and even began in the more recent basins – for a long time, perhaps after that of the Seine had been completely filled, and that these later formations – Quaternary (1), so to say – should not retain the name of alluvial deposits any more than the true and ancient tertiary deposits, from which they must also be distinguished.) However, on the very same page, Desnoyers abandoned the use of the term "quaternary" because the distinction between quaternary and tertiary deposits wasn't clear. From p. 193: "La crainte de voir mal comprise … que ceux du bassin de la Seine." (The fear of seeing my opinion in this regard be misunderstood or exaggerated, has made me abandon the word "quaternary", which at first I had wanted to apply to all deposits more recent than those of the Seine basin.)</ref><ref>{{#invoke:citation/CS1|citation
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The Quaternary Period follows the Neogene Period and extends to the present. The Quaternary covers the time span of glaciations classified as the Pleistocene, and includes the present interglacial time-period, the Holocene.
This places the start of the Quaternary at the onset of Northern Hemisphere glaciation approximately 2.6 million years ago (mya). Prior to 2009, the Pleistocene was defined to be from 1.805 million years ago to the present, so the current definition of the Pleistocene includes a portion of what was, prior to 2009, defined as the Pliocene.
Quaternary stratigraphers usually worked with regional subdivisions. From the 1970s, the International Commission on Stratigraphy (ICS) tried to make a single geologic time scale based on GSSP's, which could be used internationally. The Quaternary subdivisions were defined based on biostratigraphy instead of paleoclimate.
This led to the problem that the proposed base of the Pleistocene was at 1.805 million years ago, long after the start of the major glaciations of the northern hemisphere. The ICS then proposed to abolish use of the name Quaternary altogether, which appeared unacceptable to the International Union for Quaternary Research (INQUA).
In 2009, it was decided to make the Quaternary the youngest period of the Cenozoic Era with its base at 2.588 mya and including the Gelasian Stage, which was formerly considered part of the Neogene Period and Pliocene Epoch.<ref name="ICS2009">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This was later revised to 2.58 mya.<ref name="ICS StratChart 2022-02" /><ref name="ICS StratChart Revisions">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The Anthropocene was proposed as a third epoch as a mark of the anthropogenic impact on the global environment starting with the Industrial Revolution, or about 200 years ago.<ref name="Zalasiewicz2011">Template:Cite journal</ref> The Anthropocene was rejected as a geological epoch in 2024 by the International Union of Geological Sciences (IUGS), the governing body of the ICS.<ref name="IUGS2024">The Anthropocene: IUGS-ICS Statement. March 20, 2024/https://www.iugs.org/_files/ugd/f1fc07_ebe2e2b94c35491c8efe570cd2c5a1bf.pdf</ref>
GeologyEdit
Template:Further The 2.58 million years of the Quaternary represents the time during which recognisable humans existed.<ref name="autogenerated1">Template:Cite news</ref> Over this geologically short time period there has been relatively little change in the distribution of the continents due to plate tectonics.
The Quaternary geological record is preserved in greater detail than that for earlier periods.
The major geographical changes during this time period included the emergence of the straits of Bosphorus and Skagerrak during glacial epochs, which respectively turned the Black Sea and Baltic Sea into fresh water lakes, followed by their flooding (and return to salt water) by rising sea level;<ref>Template:Cite journal</ref> the periodic filling of the English Channel, forming a land bridge between Britain and the European mainland; the periodic closing of the Bering Strait, forming the land bridge between Asia and North America; and the periodic flash flooding of Scablands of the American Northwest by glacial water.<ref name="Balbas2017a">Balbas, A.M., Barth, A.M., Clark, P.U., Clark, J., Caffee, M., O'Connor, J., Baker, V.R., Konrad, K. and Bjornstad, B., 2017. 10Be dating of late Pleistocene megafloods and Cordilleran Ice Sheet retreat in the northwestern United States. Geology, 45(7), pp. 583-586.</ref>
The current extent of Hudson Bay, the Great Lakes and other major lakes of North America are a consequence of the Canadian Shield's readjustment since the last ice age; different shorelines have existed over the course of Quaternary time.<ref>Template:Cite journal</ref>
ClimateEdit
The climate was one of periodic glaciations with continental glaciers moving as far from the poles as 40 degrees latitude. Glaciation took place repeatedly during the Quaternary Ice age – a term coined by Schimper in 1839 that began with the start of the Quaternary about 2.58 Mya and continues to the present day.
In 1821, a Swiss engineer, Ignaz Venetz, presented an article in which he suggested the presence of traces of the passage of a glacier at a considerable distance from the Alps. This idea was initially disputed by another Swiss scientist, Louis Agassiz, but when he undertook to disprove it, he ended up affirming his colleague's hypothesis. A year later, Agassiz raised the hypothesis of a great glacial period that would have had long-reaching general effects. This idea gained him international fame and led to the establishment of the Glacial Theory.
In time, thanks to the refinement of geology, it has been demonstrated that there were several periods of glacial advance and retreat and that past temperatures on Earth were very different from today. In particular, the Milankovitch cycles of Milutin Milankovitch are based on the premise that variations in incoming solar radiation are a fundamental factor controlling Earth's climate.
During this time, substantial glaciers advanced and retreated over much of North America and Europe, parts of South America and Asia, and all of Antarctica.
Flora and faunaEdit
Template:Expand section Template:Further There was a major extinction of large mammals globally during the Late Pleistocene Epoch.<ref>Template:Cite journal</ref> Many forms such as sabre-toothed cats, mammoths, mastodons, glyptodonts, etc., became extinct worldwide. Others, including horses, camels and American cheetahs became extinct in North America.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The Great Lakes formed and giant mammals thrived in parts of North America and Eurasia not covered in ice. These mammals became extinct when the glacial period ended about 11,700 years ago. Modern humans evolved about 315,000 years ago. During the Quaternary Period, mammals, flowering plants, and insects dominated the land. Template:Citation needed
See alsoEdit
ReferencesEdit
External linksEdit
- Subcommission on Quaternary Stratigraphy
- Stratigraphical charts for the Quaternary
- Version history of the global Quaternary chronostratigraphical charts (from 2004b)
- Silva, P.G. C. Zazo, T. Bardají, J. Baena, J. Lario, A. Rosas, J. Van der Made. 2009, "Tabla Cronoestratigrafíca del Cuaternario en la Península Ibérica - V.2". [Versión PDF, 3.6 Mb]. Asociación Española para el Estudio del Cuaternario (AEQUA), Departamento de Geología, Universidad de Salamanca, Spain. (Correlation chart of European Quaternary and cultural stages and fossils)
- Welcome to the XVIII INQUA-Congress, Bern, 2011 Template:Webarchive
- Quaternary (chronostratigraphy scale)
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