Editing Cryogenian (section)

==Climate==

The name of the geologic period refers to the very cold global climate of the Cryogenian.

Characteristic glacial deposits indicate that [[Earth]] suffered the most severe ice ages in its history during this period (Sturtian and Marinoan). According to Eyles and Young, "Late Proterozoic glaciogenic deposits are known from all the continents.  They provide evidence of the most widespread and long-ranging glaciation on Earth." Several glacial periods are evident, interspersed with periods of relatively warm climate, with glaciers reaching sea level in low paleolatitudes.<ref name="Eyles-1994">{{cite book|last1=Eyles|first1=Nicholas|last2=Young|first2=Grant|editor1-last=Deynoux|editor1-first=M.|editor2-last=Miller|editor2-first=J.M.G.|editor3-last=Domack|editor3-first=E.W.|editor4-last=Eyles|editor4-first=N.|editor5-last=Fairchild|editor5-first=I.J.|editor6-last=Young|editor6-first=G.M.|editor-link3=Eugene Domack|title=Geodynamic controls on glaciation in Earth history, in Earth's Glacial Record|date=1994|publisher=Cambridge University Press|location=Cambridge|isbn=0521548039|pages=[https://archive.org/details/earthsglacialrec0000unse/page/5 5–10]|url=https://archive.org/details/earthsglacialrec0000unse/page/5}}</ref>

[[Glacier]]s extended and contracted in a series of rhythmic pulses, possibly reaching as far as the equator.<ref>{{cite web |title = Microfossil lineages support sloshy snowball Earth |author = Dave Lawrence |year = 2003 |publisher = Geotimes |url = http://www.agiweb.org/geotimes/apr03/WebExtra041803.html}}</ref>

[[File:Elatina Fm diamictite.JPG|thumb|[[Diamictite]] of the Elatina Formation in South Australia, formed during the Marinoan glaciation of the late Cryogenian]]
The Cryogenian is generally considered to be divisible into at least two major worldwide glaciations. The [[Sturtian glaciation]] persisted from 720 to 660 million years ago, and the [[Marinoan glaciation]] which ended approximately 635 Ma, at the end of the Cryogenian.<ref>{{Cite journal | last1 = Shields | first1 = G. A. | title = Palaeoclimate: Marinoan meltdown | doi = 10.1038/ngeo214 | journal = Nature Geoscience | volume = 1 | issue = 6 | pages = 351–353 | year = 2008 |bibcode = 2008NatGe...1..351S }}</ref> The deposits of glacial [[tillite]] also occur in places that were at low latitudes during the Cryogenian, a phenomenon which led to the hypothesis of deeply frozen planetary oceans called "[[Snowball Earth]]".<ref>Hoffman, P.F. 2001. [http://www.snowballearth.org ''Snowball Earth theory'']</ref> Between the Sturtian and Marinoan glaciations was a so-called "Cryogenian interglacial period" marked by relatively warm climate and [[Anoxic event|anoxic oceans]],<ref name="Xu-2019">{{Cite journal |last1=Xu |first1=Lingang |last2=Frank |first2=Anja B. |last3=Lehmann |first3=Bernd |last4=Zhu |first4=Jianming |last5=Mao |first5=Jingwen |last6=Ju |first6=Yongze |last7=Frei |first7=Robert |date=21 October 2019 |title=Subtle Cr isotope signals track the variably anoxic Cryogenian interglacial period with voluminous manganese accumulation and decrease in biodiversity |journal=[[Scientific Reports]] |language=en |volume=9 |issue=1 |page=15056 |doi=10.1038/s41598-019-51495-0 |issn=2045-2322 |pmc=6803686 |pmid=31636318 |bibcode=2019NatSR...915056X }}</ref> along with marine transgression.<ref>{{Cite journal |last1=Freitas |first1=B.T. |last2=Rudnitzki |first2=I.D. |last3=Morais |first3=L. |last4=Campos |first4=M.D.R. |last5=Almeida |first5=R.P. |last6=Warren |first6=L.V. |last7=Boggiani |first7=P.C. |last8=Caetano-Filho |first8=S. |last9=Bedoya-Rueda |first9=C. |last10=Babinski |first10=M. |last11=Fairchild |first11=T.R. |last12=Trindade |first12=R.I.F. |date=30 August 2021 |title=Cryogenian glaciostatic and eustatic fluctuations and massive Marinoan-related deposition of Fe and Mn in the Urucum District, Brazil |url=https://pubs.geoscienceworld.org/geology/article/49/12/1478/607268/Cryogenian-glaciostatic-and-eustatic-fluctuations |journal=[[Geology (journal)|Geology]] |language=en |volume=49 |issue=12 |pages=1478–1483 |doi=10.1130/G49134.1 |bibcode=2021Geo....49.1478F |hdl=11449/222880 |s2cid=239629114 |issn=0091-7613 |access-date=11 September 2023}}</ref>