{{Short description|Glacial episode}} The '''Pongola glaciation''' was a glacial period that occurred in the [[Mesoarchean]], from around 2.985-2.837 billion years ago. It is the oldest known glaciation on [[Earth]].
== Geology == The oldest known traces of glaciation date from the [[Mesoarchean]]. They correspond to the [[diamictite]] of the Pongola supergroup{{sfn|Kopp|Kirschvink|Hilburn|Nash|2005|p=}} (more precisely to the Mozaan formation,{{sfn|USGS|2008|p=86}}) in [[KwaZulu-Natal]] and in [[Eswatini]].{{sfn|University of KwaZulu-Natal}}
== Climate == Even if the climate of the Mesoarchean is not well known, the study of the [[oxygen isotopes]] in the [[Chert|cherts]] of the time seem to show that the climate of the Mesoarchean was warm or, at least, temperate,{{sfn|Kasting|Howard|2006}} in particular due to high levels of [[methane]] and [[carbon dioxide]] in the atmosphere; a glaciation is therefore likely to have been caused by a drop in the rate of these greenhouse gases.{{sfn|Kasting|Ono|2006}}{{sfn|Young|von Brunn|Gold|Minter|1998}} The Pongola glaciation is also associated with changes in sulfur isotopes ([[Δ34S|δ<sup>34</sup>S]]), suggesting that this may also involve early and short-lived oxygenation of the Earth's atmosphere.{{sfn|Zalasiewicz|Williams|2012|p=30}}{{sfn|USGS|2008|pp=86-87}}
== Extension == The extension of the glaciation is not determined with certainty.{{sfn|Deconinck}}{{sfn|USGS|2008|pp=86-87}} Some authors argue that the glacial deposits were formed at low latitudes, below 30° N,{{sfn|El Albani|Macchiarelli|Meunier|2016|p=15}} therefore close to the tropics, which would imply extensive glaciation, while others argue that the area was located at mid-latitude or even high latitude, closer to the pole, where a polar glacier could have formed, like the current situation.{{sfn|USGS|2008|p=87}}{{sfn|Zalasiewicz|Williams|2012|p=23}}
Regarding its duration, the corresponding glacial deposits fall within the interval 2.985 ± 1 and 2.837 ± 5 Bya.{{sfn|USGS|2008|pp=86-87}}{{sfn|Zalasiewicz|Williams|2012|p=16}}
== See also == {{Portal|Geology}} * [[Huronian glaciation]]
== References == {{Reflist}}
== Bibliography == * {{Cite web |first=J.F. |last=Deconinck |title=Variabilité climatique et cycles géodynamiques |url=http://planet-terre.ens-lyon.fr/planetterre/objets/Images/FT07/climat-geodynamique-Deconinck.pdf |publisher=CNRS |language=fr}} * {{Cite web |title=Pongola supergroup. The first record of ancient life |url=http://www.stec.ukzn.ac.za/geologyeducationmuseum/kzngeology/pongolasupergroup.aspx |publisher=University of KwaZulu-Natal |language=en |ref={{sfnref|University of KwaZulu-Natal}} }} * {{Cite journal |last1=Young |first1=Grant M. |last2=von Brunn |first2=Victor |last3=Gold |first3=Digby J. C. |last4=Minter |first4=W. E. L. |year=1998 |title=Earth's Oldest Reported Glaciation: Physical and Chemical Evidence from the Archean Mozaan Group (~2.9 Ga) of South Africa |journal=The Journal of Geology |language=en |volume=106 |issue=5 |page=523-538 |doi=10.1086/516039|s2cid=129717765 }} * {{Cite journal |first1=Robert E. |last1=Kopp |first2=Joseph L. |last2=Kirschvink |first3=Isaac A. |last3=Hilburn |first4=Cody Z. |last4=Nash |date=9 August 2005 |title=The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis |journal=PNAS |language=en |volume=102 |issue=32 |pages=11131–11136 |doi=10.1073/pnas.0504878102 |pmid=16061801 |pmc=1183582 |doi-access=free }} * {{Cite journal |last1=Gold |first1=D.J.C. |last2=Johnson |first2=M.R. |last3=Anhaeusser |first3=C.R. |last4=Thomas |first4=Bob |year=2006 |title=The Pongola Supergroup. The geology of South Africa |journal=Geol. Soc. South Afr. |language=en |page=135-148}} * {{Cite journal |first1=James F. |last1=Kasting |first2=Shuhei |last2=Ono |date=29 June 2006 |title=Palaeoclimates: the first two billion years |journal=Philosophical Transactions B |language=en |volume=361 |issue=1470 |pages=917–929 |doi=10.1098/rstb.2006.1839|pmid=16754607 |pmc=1868609 }} * {{Cite journal |last1=Kasting |first1=James F. |last2=Howard |first2=M. Tazewell |date=29 October 2006 |title=Atmospheric composition and climate on the early Earth |journal=Philosophical Transactions B |language=en |volume=361 |issue=1474 |pages=1733–1742 |doi=10.1098/rstb.2006.1902|pmid=17008214 |pmc=1664689 }} * {{Cite book |url=https://books.google.com/books?id=LwlSAgAAQBAJ&pg=PA86 |title=Antarctica: A Keystone in a Changing World |publisher=National Academies Press |year=2008 |isbn=9780309118545 |language=en |ref={{sfnref|USGS|2008}} }} * {{Cite book |first1=Jan |last1=Zalasiewicz |first2=Mark |last2=Williams |url=https://books.google.com/books?id=p4dP2t8rnJ0C&pg=PA22 |title=The Goldilocks Planet: The 4 billion year story of Earth's climate |publisher=Oxford University Press |year=2012 | isbn=978-0-19-959357-6 |language=en}} * {{Cite book |last=Alain R. Meunier |title=La naissance de la Terre |publisher=Dunod |year=2014 |page=235 |language=fr}} * {{Cite book |last1=El Albani |first1=Abderrazak |url=https://books.google.com/books?id=8rSpCwAAQBAJ&pg=PT15 |title=Aux origines de la vie: Une nouvelle histoire de l'évolution |last2=Macchiarelli |first2=Roberto |last3=Meunier |first3=Alain R. |publisher=Dunod |year=2016 |isbn=9782100748259 |language=fr}}
{{Ice ages}}
[[Category:Geology of Eswatini]] [[Category:Geology of South Africa]] [[Category:Ice ages]] [[Category:Geography of KwaZulu-Natal]]