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Science 8 April 2005:
Vol. 308. no. 5719, pp. 239 - 242
DOI: 10.1126/science.1104657
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Reports

Estimating Duration and Intensity of Neoproterozoic Snowball Glaciations from Ir Anomalies

Bernd Bodiselitsch,1 Christian Koeberl,1* Sharad Master,2 Wolf U. Reimold2

The Neoproterozoic glaciations supposedly ended in a supergreenhouse environment, which led to rapid melting of the ice cover and precipitation of the so-called cap carbonates. If Earth was covered with ice, then extraterrestrial material would have accumulated on and within the ice and precipitated during rapid melting at the end of the glaciation. We found iridium (Ir) anomalies at the base of cap carbonates in three drill cores from the Eastern Congo craton. Our data confirm the presence of extended global Neoproterozoic glaciations and indicate that the duration of the Marinoan glacial episode was at least 3 million, and most likely 12 million, years.

1 Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria.
2 Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa.

* To whom correspondence should be addressed. E-mail: christian.koeberl{at}univie.ac.at

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Science. ISSN 0036-8075 (print), 1095-9203 (online)