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. It forms the second geologic period of the
Neoproterozoic Era, preceded by the
Tonian Period and followed by the
The Sturtian and Marinoan glaciations occurred during the Cryogenian
period, 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").
Cryogenian biota and fossils
5 In popular culture
6 See also
8 Further reading
Cryogenian period was ratified in 1990 by the International
Commission on Stratigraphy. 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,
until 2015, when it was changed to 720 million years.
This is problematic because estimates of rock ages are variable and
are subject to laboratory error. For instance, the time scale of the
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 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.
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
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
Glaciers extended and contracted in a series of rhythmic pulses,
possibly reaching as far as the equator.
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. 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
Rodinia § Geodynamics
Before the start of the Cryogenian, around 750 Ma, the cratons that
made up the supercontinent
Rodinia started to rift apart. The
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
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. The Sturtian and Marinoan are local divisions within
the Adelaide Rift Complex.
Cryogenian biota and fossils
Fossils of testate amoeba (or Arcellinida) first appear during the
Cryogenian period. During the
Cryogenian period, the oldest known
fossils of sponges (and therefore animals) make an
appearance. 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.
In popular culture
The Time Travellers Guide to Australia (2012) on IMDb
Miracle Planet :
Snowball Earth on
YouTube (2010s) BBC/CBC/NHK
Timeline of glaciation
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 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,
^ 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
^ Plumb, Kenneth A. (1991). "New
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 history, in Earth's Glacial
Record. Cambridge: Cambridge University Press. pp. 5–10.
^ Dave Lawrence (2003). "Microfossil lineages support sloshy snowball
^ Shields, G. A. (2008). "Palaeoclimate: Marinoan meltdown". Nature
Geoscience. 1 (6): 351–353. Bibcode:2008NatGe...1..351S.
^ Hoffman, P.F. 2001.
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.
^ 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.
^ "Discovery of possible earliest animal life pushes back fossil
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.
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.
Hoffman, Paul F.; Abbot, Dorian S.; et al. (November 8, 2017).
Snowball Earth climate dynamics and
Science Advances. American Association for the Advancement of Science.
3 (11). Retrieved 20 January 2018. CS1 maint: Explicit use of et
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
Karoo (360 Mya to 260 Mya)
Andean-Saharan (460 Mya to 430 Mya)
Gaskiers (579.63 to 579.63 Mya)
Baykonurian (547 to 541.5 Mya)
Sturtian (717 to 660 Mya); Marinoan (650 to 635 Mya)
Huronian (2.4 to 2.1 Gya)
Pongola (2.9 to 2.78 Gya)
Greenhouse and icehouse Earth
Great Oxygenation Event
Timeline of glaciation