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The Cryogenian ( /kraɪoʊˈdʒɛniən/, from Greek κρύος (krýos), meaning "cold" and γένεσις (génesis), meaning "birth") is a geologic period that lasted from 720 to 635 million years ago.[9] It forms the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by the Ediacaran. The Sturtian and Marinoan glaciations occurred during the Cryogenian period,[10] which are the greatest ice ages known to have occurred on Earth. These events are the subject of much scientific controversy. The main debate contests whether these glaciations covered the entire planet (the so-called "Snowball Earth") or a band of open sea survived near the equator (termed "slushball Earth").

Contents

1 Ratification 2 Climate 3 Paleogeography 4 Cryogenian biota and fossils 5 In popular culture 6 See also 7 References 8 Further reading

Ratification[edit] The Cryogenian period was ratified in 1990 by the International Commission on Stratigraphy.[11] In contrast to most other time periods, the beginning of the Cryogenian is not linked to a globally observable and documented event. Instead, the base of the period is defined by a fixed rock age, that was set at 850 million years,[12] until 2015, when it was changed to 720 million years.[9] This is problematic because estimates of rock ages are variable and are subject to laboratory error. For instance, the time scale of the Cambrian
Cambrian
Period is not reckoned by rock younger than a given age (541 million years), but by the appearance of the worldwide Treptichnus pedum diagnostic trace fossil assemblages. This means that rocks can be recognized as Cambrian
Cambrian
when examined in the field and do not require extensive testing to be performed in a lab to find a date. Currently, there is no consensus on what global event is a suitable candidate to mark the start of the Cryogenian Period, but a global glaciation would be a likely candidate.[12] Climate[edit] The name of the geologic period refers to the very cold global climate of the Cryogenian. Characteristic glacial deposits indicate that Earth
Earth
suffered the most severe ice ages in its history during this period (Sturtian and Marinoan). According to Eyles and Young, "Late Proterozoic
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.[13] Glaciers extended and contracted in a series of rhythmic pulses, possibly reaching as far as the equator.[14] 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
Marinoan glaciation
which ended approximately 635 Ma, at the end of the Cryogenian.[15] 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".[16] Paleogeography[edit] Main article: Rodinia
Rodinia
§ Geodynamics Before the start of the Cryogenian, around 750 Ma, the cratons that made up the supercontinent Rodinia
Rodinia
started to rift apart. The superocean Mirovia
Mirovia
began to close while the superocean Panthalassa began to form. The cratons (possibly) later assembled into another supercontinent called Pannotia, in the Ediacaran. Eyles and Young state, "Most Neoproterozoic glacial deposits accumulated as glacially influenced marine strata along rifted continental margins or interiors." Worldwide deposition of dolomite might have reduced atmospheric carbon dioxide. The break up along the margins of Laurentia
Laurentia
at about 750 Ma occurs at about the same time as the deposition of the Rapitan Group in North America, contemporaneously with the Sturtian in Australia. A similar period of rifting at about 650 Ma occurred with the deposition of the Ice Brook Formation in North America, contemporaneously with the Marinoan in Australia.[13] The Sturtian and Marinoan are local divisions within the Adelaide Rift Complex. Cryogenian biota and fossils[edit] Fossils of testate amoeba (or Arcellinida) first appear during the Cryogenian period.[17] During the Cryogenian period, the oldest known fossils of sponges (and therefore animals) make an appearance.[18][19][20] The issue of whether or not biology was impacted by this event has not been settled, for example Porter (2000) suggests that new groups of life evolved during this period, including the red algae and green algae, stramenopiles, ciliates, dinoflagellates, and testate amoeba.[21] In popular culture[edit]

The Time Travellers Guide to Australia (2012) on IMDb Miracle Planet : Snowball Earth
Snowball Earth
on YouTube
YouTube
(2010s) BBC/CBC/NHK

See also[edit]

Timeline of glaciation

References[edit]

^ Image:Sauerstoffgehalt-1000mj.svg ^ File:OxygenLevel-1000ma.svg ^ Image: Phanerozoic
Phanerozoic
Carbon Dioxide.png ^ Image:All palaeotemps.png ^ a b Arnaud, Emmanuelle; Halverson, Galen P.; Shields-Zhou, Graham Anthony (30 November 2011). "Chapter 1 The geological record of Neoproterozoic ice ages". Memoirs. Geological Society of London. 36 (1): 1–16. doi:10.1144/M36.1.  ^ Pu, Judy P.; Bowring, Samuel A.; Ramezani, Jahandar; Myrow, Paul; Raub, Timothy D.; Landing, Ed; Mills, Andrea; Hodgin, Eben; MacDonald, Francis A. (2016). "Dodging snowballs: Geochronology of the Gaskiers glaciation and the first appearance of the Ediacaran
Ediacaran
biota". Geology. 44 (11): 955. doi:10.1130/G38284.1.  ^ Macdonald, F. A.; Schmitz, M. D.; Crowley, J. L.; Roots, C. F.; Jones, D. S.; Maloof, A. C.; Strauss, J. V.; Cohen, P. A.; Johnston, D. T.; Schrag, D. P. (4 March 2010). "Calibrating the Cryogenian". Science. 327 (5970): 1241–1243. doi:10.1126/science.1183325. PMID 20203045.  (Duration and magnitude are enigmatic) ^ "Press release: Discovery of Possible Earliest Animal Life Pushes Back Fossil Record". National Science Foundation. August 17, 2010.  ^ a b "Chart". International Commission on Stratigraphy. Archived from the original on 2017-01-13. Retrieved 2017-02-14.  ^ These events were formerly considered together as the Varanger glaciations, from their first detection in Norway's Varanger Peninsula. ^ Plumb, Kenneth A. (1991). "New Precambrian
Precambrian
time scale" (PDF). Episode. 2. 14: 134–140. Retrieved 7 September 2013.  ^ a b "GSSP Table - Precambrian". Geologic Timescale Foundation. Retrieved 7 September 2013.  ^ a b Eyles, Nicholas; Young, Grant (1994). Deynoux, M.; Miller, J.M.G.; Domack, E.W.; Eyles, N.; Fairchild, I.J.; Young, G.M., eds. Geodynamic controls on glaciation in Earth
Earth
history, in Earth's Glacial Record. Cambridge: Cambridge University Press. pp. 5–10. ISBN 0521548039.  ^ Dave Lawrence (2003). "Microfossil lineages support sloshy snowball Earth". Geotimes.  ^ Shields, G. A. (2008). "Palaeoclimate: Marinoan meltdown". Nature Geoscience. 1 (6): 351–353. Bibcode:2008NatGe...1..351S. doi:10.1038/ngeo214.  ^ Hoffman, P.F. 2001. Snowball Earth
Snowball Earth
theory ^ Porter, S.A. & Knoll, A.H. (2000). "Testate amoeba in the Neoproterozoic Era: evidence from vase-shaped microfossils in the Chuar Group, Grand Canyon". Paleobiology. 26 (3): 360–385. doi:10.1666/0094-8373(2000)026<0360:TAITNE>2.0.CO;2. ISSN 0094-8373.  ^ Love; Grosjean, Emmanuelle; Stalvies, Charlotte; Fike, David A.; Grotzinger, John P.; Bradley, Alexander S.; Kelly, Amy E.; Bhatia, Maya; Meredith, William; et al. (2009). "Fossil steroids record the appearance of Demospongiae during the Cryogenian period" (PDF). Nature. 457 (7230): 718–721. Bibcode:2009Natur.457..718L. doi:10.1038/nature07673. PMID 19194449.  ^ Maloof, Adam C.; Rose, Catherine V.; Beach, Robert; Samuels, Bradley M.; Calmet, Claire C.; Erwin, Douglas H.; Poirier, Gerald R.; Yao, Nan; Simons, Frederik J. (17 August 2010). "Possible animal-body fossils in pre-Marinoan limestones from South Australia". Nature Geoscience. 3 (9): 653–659. Bibcode:2010NatGe...3..653M. doi:10.1038/ngeo934.  ^ "Discovery of possible earliest animal life pushes back fossil record". 2010-08-17.  ^ http://palaeos.com/proterozoic/neoproterozoic/cryogenian/cryogenian2.html

Further reading[edit]

" Cryogenian Period". GeoWhen Database. Archived from the original on December 2, 2005. Retrieved January 5, 2006.  James G. Ogg (2004). "Status on Divisions of the International Geologic Time Scale". Lethaia. 37 (2): 183–199. doi:10.1080/00241160410006492.  Brain, C. K.; Prave, A. R.; Hoffmann, K. H.; Fallick, A. E.; Herd, D. A.; Sturrock, C.; Young, I.; Condon, D. J.; Allison, S. G. (2012). "The first animals: ca. 760-million-year-old sponge-like fossils from Namibia". South African Journal of Science. 108: 1–8. doi:10.4102/sajs.v108i1/2.658.  Hoffman, Paul F.; Abbot, Dorian S.; et al. (November 8, 2017). " Snowball Earth
Snowball Earth
climate dynamics and Cryogenian geology-geobiology". Science Advances. American Association for the Advancement of Science. 3 (11). Retrieved 20 January 2018. CS1 maint: Explicit use of et al. (link)

v t e

Proterozoic
Proterozoic
Eon

Paleoproterozoic Era Mesoproterozoic Era Neoproterozoic Era

Siderian Rhyacian Orosirian Statherian

Calymmian Ectasian Stenian

Tonian Cryogenian Ediacaran

v t e

Ice ages

Quaternary

Current

Antarctica Greenland Iceland

Pleistocene

Last glacial period 1st: Würm, Wisconsin, Weichselian, Devensian/Midlandian, Pinedale/Fraser, Greenland, Merida, Llanquihue 2nd: Riss, Illinoian, Saale, Wolstonian, Santa María 3rd–6th: Mindel, Pre-Illinoian, Elster, Anglian, Rio Llico 7th–8th: Günz, Pre-Illinoian, Elbe or Menapian, Beestonian, Caracol

Carboniferous–Permian

Karoo (360 Mya to 260 Mya)

Ordovician–Silurian

Andean-Saharan (460 Mya to 430 Mya)

Ediacaran

Gaskiers (579.63 to 579.63 Mya) Baykonurian (547 to 541.5 Mya)

Cryogenian

Sturtian (717 to 660 Mya); Marinoan (650 to 635 Mya)

Paleoproterozoic

Huronian (2.4 to 2.1 Gya)

Mesoarchean

Pongola (2.9 to 2.78 Gya)

Related topics

Greenhouse and icehouse Earth Great Oxygenation Event Snowball Earth Interglacial Milankovitch cycles Stadial

Timeline of glaciation

Geology
Geology
portal P

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