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Nature. 2008 Jun 5;453(7196):767-9. doi: 10.1038/nature07072. Epub 2008 May 28.

Hydrogen sulphide release to surface waters at the Precambrian/Cambrian boundary.

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  • 1Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012 Bern, Switzerland. martin.wille@anu.edu.au

Abstract

Animal-like multicellular fossils appeared towards the end of the Precambrian, followed by a rapid increase in the abundance and diversity of fossils during the Early Cambrian period, an event also known as the 'Cambrian explosion'. Changes in the environmental conditions at the Precambrian/Cambrian transition (about 542 Myr ago) have been suggested as a possible explanation for this event, but are still a matter of debate. Here we report molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 Myr. We find a transient molybdenum isotope signal immediately after the Precambrian/Cambrian transition. Using a box model of the oceanic molybdenum cycle, we find that intense upwelling of hydrogen sulphide-rich deep ocean water best explains the observed Early Cambrian molybdenum isotope signal. Our findings suggest that the Early Cambrian animal radiation may have been triggered by a major change in ocean circulation, terminating a long period during which the Proterozoic ocean was stratified, with sulphidic deep water.

Comment in

  • Early Cambrian ocean anoxia in South China. [Nature. 2009]
PMID:
18509331
[PubMed - indexed for MEDLINE]
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