Australia: The Land Where Time Began

A biography of the Australian continent 

Snowball Earth - an Interglacial? Dynamic Behaviour of Ice in the Chuos Formation, Namibia

According to the authors1 the Sturtian Glaciation, at about 716 Ma, was the earliest glaciation that occurred in the Cryogenian. Glaciogenic strata of the Chuos Formation, representing the Sturtian Glaciation, have been found at Omutirapo, northern Namibia, that fill a palaeovalley that is 2 km wide and 400 m deep. When the authors1 carried out sedimentary logging of an exposure that was of exceptionally high quality, it allowed them to produce detailed descriptions and interpretations, the results revealing the presence in the sediments of 2 glacial cycles. Strong evidence was found at the base of the exposed succession, including diamictites, ice-rafted dropstones and zones of intense shearing, that they interpreted as being of subglacial origin, all of which supports glaciation. Collectively, these facies represent ice-proximal to ice-rafted deposits. Upstream, mudstones that were free of dropstones were present in the middle of the succession, and the absence of diamictite implies sedimentation was not influenced by glaciation, glacial deposits are again found in overlying strata indicate another phase of glaciation of the Sturtian Glaciation. When comparisons were made with strata that were age-equivalent in South Australia, a location where previous study had found evidence that sediments were free of sea-ice, suggests there may have been an extensive interglacial, which implies the waxing and waning of ice sheets on a global scale during a Cryogenian glacial event.

Sources & Further reading

  1. Le Heron, Daniel P., Marie E. Busfield, and Fred Kamona. "An Interglacial on Snowball Earth? Dynamic Ice Behaviour Revealed in the Chuos Formation, Namibia." Sedimentology 60, no. 2 (2013): 411-27.


Author: M. H. Monroe
Last updated  02/06/2013

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