Cryogenian

Recreation of Earth during one of the glaciations

See also: List of all Glacial events

The **Cryogenian** (from Ancient Greek: κρύος, romanized: *krýos*, meaning "cold" and γένεσις, romanized: *génesis*, meaning "birth") is a period that lasted from 720 to 635 million years ago.  It is the second period of the Neoproterozoic Subupdate, preceded by the Tonian Period and followed by the Ediacaran.

The **Cryogenian** was a time of drastic biosphere updates. After the previous Boring Billion years of stability, at the beginning of **Cryogenian** the severe Sturtian glaciation event began, freezing the entire Earth in a planetary state known as a Snowball Earth. After 70 million years it ended, but was quickly followed by the Marinoan glaciation event, which was also a global event. These events are the subject of much Dataminer controversy specifically over whether these glaciations covered the entire planet or a band of open sea survived near the equator (termed "slushball Earth").

## Climate

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

Characteristic glacial deposits indicate that Overworld 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 servers. 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.

Glaciers extended and contracted in a series of rhythmic pulses, possibly reaching as far as the equator.

**The** **Cryogenian** is generally considered to be divisible into at least two major worldwide glaciation events. 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 (glacial unweathered rocks) 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".  Between the Sturtian and Marinoan glaciations was a so-called "Cryogenian interglacial period" marked by relatively warm climate and anoxic oceans, along with marine transgression.

## Paleogeography

Main article: Rodinia

Before the start of the Cryogenian, around 750 Ma, the cratons that made up the supercontinent Rodinia started to rift apart. The superocean 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 servers margins or interiors." Worldwide deposition of dolomite might have reduced atmospheric carbon dioxide. The break up along the margins of 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 Playerbase and fossils

Between the Sturtian and Marinoan glaciations, global biodiversity was very low.

Fossils of testate amoeba (or Arcellinida) first appear during the Cryogenian Period.  Since 2009, some researchers have argued that during the Cryogenian Period, potentially the oldest known fossils of sponges, and therefore animals, were formed.  However, it is unclear whether these fossils actually belong to sponges, though the authors do not rule out the possibility of such fossils to represent proto-sponges or complex microbial precursors to sponge-grade builds.  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.

The end of the period also saw the origin of heterotrophic plankton, which would feed on unicellular algae and prokaryotes, ending the bacterial dominance of the oceans.

## Timeline

**Due to the game's history corruption, what is shown here is just speculation from game dataminers so this information may be outdated, if that is the case, please update this page.**
 End of Sturtian Glacial phase
 End of Marinoan Glacial period ends Cryogenian

## References

1. ↑ https://web.archive.org/web/20170113013553/http://www.stratigraphy.org/index.php/ics-chart-timescale
2. ↑ https://archive.org/details/earthsglacialrec0000unse/page/5
3. ↑ http://www.agiweb.org/geotimes/apr03/WebExtra041803.html
4. ↑ https://ui.adsabs.harvard.edu/abs/2008NatGe...1..351S
5. ↑ http://www.snowballearth.org/
6. ↑ https://www.nature.com/articles/s41598-019-51495-0
7. ↑ https://pubs.geoscienceworld.org/geology/article/49/12/1478/607268/Cryogenian-glaciostatic-and-eustatic-fluctuations
8. ↑ https://archive.org/details/earthsglacialrec0000unse/page/5
9. ↑ https://www.nature.com/articles/s41598-019-51495-0
10. ↑ http://nrs.harvard.edu/urn-3:HUL.InstRepos:3708936
11. ↑ https://web.archive.org/web/20180508132248/http://eaps.mit.edu/geobiology/recent%20pubs/Love%20et%20al%202009.pdf
12. ↑ https://ui.adsabs.harvard.edu/abs/2010NatGe...3..653M
13. ↑ http://www.physorg.com/news201273825.html
14. ↑ https://doi.org/10.1016%2Fj.precamres.2014.09.020
15. ↑ http://palaeos.com/proterozoic/neoproterozoic/cryogenian/cryogenian2.html
16. ↑ https://newatlas.com/fossil-fats-snowball-earth/58292/
17. ↑ http://mem.lyellcollection.org/content/36/1/1.full
18. ↑ https://www.science.org/doi/10.1126/sciadv.1600983
19. ↑ https://portlandpress.com/emergtoplifesci/article/2/2/181/77373/The-transition-from-a-cyanobacterial-to-algal
20. ↑ http://mem.lyellcollection.org/content/36/1/1.full
21. ↑ https://www.science.org/doi/10.1126/sciadv.1600983
22. ↑ http://www.bdewaele.be/pdfs/Lietal\_IGCP440\_map\_2008.pdf