Re-Os geochronology of postglacial black shales in Australia: Constraints on the timing of “Sturtian” glaciation
- 1Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, Alberta T6G 2E3, Canada
- 2Department of Earth Sciences, University of Durham, Durham DH1 3LE, UK
Abstract
New Re-Os dates obtained from black shales overlying the Sturtian and Areyonga glacial deposits in southern and central Australia, respectively, challenge the prevailing consensus of three Neoproterozoic glaciations. The end of Sturtian glaciation in the Adelaide Rift Complex is constrained by a Re-Os date of 643.0 ± 2.4 Ma from the overlying Tindelpina Shale Member (basal Tapley Hill Formation). A Re-Os date of 657.2 ± 5.4 Ma for the basal Aralka Formation constrains the age of the underlying Areyonga glacial deposits in the Amadeus Basin. The Re-Os ages show that the Sturtian and Areyonga glacial deposits are younger than other radiometrically dated (ca. 685–750 Ma) Neoproterozoic glacial intervals previously regarded as possible correlatives. Thus, the “Sturtian” ice age was markedly diachronous, and/or there was more than one “Sturtian”-type glaciation. Some Neoproterozoic glacial deposits may represent the products of regional and diachronous glaciation associated with protracted breakup of the supercontinent Rodinia rather than “snowball” or “slushball” Earth ice ages.
Footnotes
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↵GSA Data Repository item 2006153, Re-Os data for the Aralka Formation and Tindelpina Shale Member, is available online at www.geosociety.org/pubs/ft2006.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.
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- Accepted 11 April 2006.
- Received 2 March 2006.
- Revision received 30 March 2006.
- Geological Society of America
