Editing Quaternary (section)

==Research history==
{{See also|Quaternary science}}
In 1759 [[Giovanni Arduino (geologist)|Giovanni Arduino]] proposed that the geological strata of northern [[Italy (geographical region)|Italy]] could be divided into four successive formations or "orders" ({{langx|it|quattro ordini}}).<ref>See:
* {{cite journal |last1=Arduino |first1=Giovanni |title=Lettera Segonda di Giovanni Arduino … sopra varie sue osservazioni fatte in diverse parti del territorio di Vicenza, ed altrove, apparenenti alla Teoria terrestre, ed alla Mineralogia |journal=Nuova Raccolta d'Opuscoli Scientifici e Filologici [New collection of scientific and philogical pamphlets] |year=1760 |volume=6 |pages=133 (cxxxiii)–180(clxxx) |trans-title=Second letter of Giovani Arduino … on his various observations made in different parts of the territory of Vincenza, and elsewhere, concerning the theory of the earth and mineralogy |language=it}}  Available at: [https://bibdig.museogalileo.it/Teca/Viewer;jsessionid=3160EE486323866602B9590459D7111B?an=323812_6 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:  {{cite journal |last1=Ell |first1=Theodore |title=Two letters of Signor Giovanni Arduino, concerning his natural observations: first full English translation. Part 2. |journal=Earth Sciences History |year=2012 |volume=31 |issue=2 |pages=168–192|doi=10.17704/eshi.31.2.c2q4076006wn7751 |bibcode=2012ESHis..31..168E }}</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 (geology)|Period]] [[rock (geology)|rocks]].<ref>{{cite journal |last1=Desnoyers |first1=J. |title=Observations sur un ensemble de dépôts marins plus récents que les terrains tertiaires du bassin de la Seine, et constituant une formation géologique distincte; précédées d'un aperçu de la nonsimultanéité des bassins tertiares |journal=Annales des Sciences Naturelles |year=1829 |volume=16 |pages=171–214, 402–491 |url=https://www.biodiversitylibrary.org/item/29350#page/177/mode/1up |trans-title=Observations on a set of marine deposits [that are] more recent than the tertiary terrains of the Seine basin and [that] constitute a distinct geological formation; preceded by an outline of the non-simultaneity of tertiary basins |language=fr}} [https://www.biodiversitylibrary.org/item/29350#page/199/mode/1up 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>{{Cite web|url=http://shodhganga.inflibnet.ac.in/bitstream/10603/77123/8/08_chapter%201.pdf|title=Late Quaternary Fluvial and Coastal Sequences Chapter 1: Introduction|access-date=26 March 2017}}</ref><ref>{{Citation|last=Wiz Science™|title=Quaternary - Video Learning |date=28 September 2015|url=https://www.youtube.com/watch?v=Io7vhansU1o| archive-url=https://web.archive.org/web/20170407105401/https://www.youtube.com/watch?v=Io7vhansU1o| archive-date=7 April 2017 | url-status=dead|access-date=26 March 2017}}</ref>

The Quaternary Period follows the [[Neogene]] Period and extends to the present. The Quaternary covers the time span of [[glacier|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&nbsp;million years ago ([[wikt:mya|mya]]). Prior to 2009, the Pleistocene was defined to be from 1.805&nbsp;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&nbsp;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&nbsp;mya and including the [[Gelasian]] Stage, which was formerly considered part of the Neogene Period and Pliocene Epoch.<ref name="ICS2009">{{cite web| url = http://www.quaternary.stratigraphy.org.uk/correlation/GSAchron09.jpg| title = See the 2009 version of the ICS geologic time scale}}</ref> This was later revised to 2.58&nbsp;mya.<ref name="ICS StratChart 2022-02" /><ref name="ICS StratChart Revisions">{{cite web | url=https://stratigraphy.org/ICSchart/ChangeLog2012-2022.txt | title=International Chronostratigraphic Chart ChangeLog for 2012-2022 | work=International Chronostratigraphic Chart | publisher=[[International Commission on Stratigraphy]] | date=February 2022 | accessdate=4 June 2022}}</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">{{cite journal |last1=Zalasiewicz |first1=J. |last2=Williams |first2=M. |last3=Haywood |first3=A. |last4=Ellis |first4=M. |title=The Anthropocene: a new epoch of geological time? |journal=Philosophical Transactions of the Royal Society A |year=2011 |volume=369 |issue=1938 |pages=835–841 |doi=10.1098/rsta.2010.0339 |ref=Zalasiewicz2011 |pmid=21282149|bibcode=2011RSPTA.369..835Z |s2cid=2624037 |url=http://nora.nerc.ac.uk/id/eprint/14867/1/Anthropocene_overview.pdf |doi-access=free }}</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>