page_title: Cryogenian
section_title: Climate
hierarchical_section_title: Cryogenian / Climate
caption_attribution_description: English: Elatina Fm diamictite, formed during the Cryogenian Period, adjacent to the Ediacaran GSSP site in Brachina Gorge, Flinders Ranges National Park; outcrop exposed in creek bed. $AUD1 coin for scale.
context_page_description: The Cryogenian 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 Ediacaran.
  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 or a band of open sea survived near the equator.
context_section_description: 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.
  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 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 Earth".
caption: Diamictite of the Elatina Formation in South Australia, formed during the Marinoan glaciation of the late Cryogenian
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