Carbon Isotopic Tests of Neoproterozoic Snowball Earth Phenomena

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The snowball Earth hypothesis proposes that during times of especially widespread glaciation some 600 to 750 million years ago, the surface ocean became completely covered with ice, resulting in the mass extinction of marine life. The occurrence of such events has important implications for the Earth's climate system as well as for the evolution of complex multicellular organisms, which appear in the fossil record immediately after the last evidence of these severe ice ages. The disruption of marine ecosystems called for in the snowball Earth hypothesis should be recorded in the carbon isotopic values of carbonate rocks deposited during the glacial event. Appropriate successions are present in Namibia, Australia and the North American Cordillera, to test this prediction, and provide insight into life in a snowball ocean. Initial results suggest life was not terribly different than before the snowball event, thus challenging the notion that sea ice was extensive enough to disrupt marine ecosystems. The data collected in this study will also be used to test other hypotheses proposed for these ice ages including the recent suggestion that post glacial massive destabilization of methane clathrates was responsible for many of the peculiar features of this record.