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Re-Os geochronology and coupled Os-Sr isotope constraints on the Sturtian snowball Earth.

Rooney, A.D. and Macdonald, F. and Strauss, J.V. and Dudás, F.Ö. and Hallmann, C. and Selby, D. (2014) 'Re-Os geochronology and coupled Os-Sr isotope constraints on the Sturtian snowball Earth.', Proceedings of the National Academy of Sciences of the United States of America., 111 (1). pp. 51-56.


After nearly a billion years with no evidence for glaciation, ice advanced to equatorial latitudes at least twice between 717 and 635 Mya. Although the initiation mechanism of these Neoproterozoic Snowball Earth events has remained a mystery, the broad synchronicity of rifting of the supercontinent Rodinia, the emplacement of large igneous provinces at low latitude, and the onset of the Sturtian glaciation has suggested a tectonic forcing. We present unique Re-Os geochronology and high-resolution Os and Sr isotope profiles bracketing Sturtian-age glacial deposits of the Rapitan Group in northwest Canada. Coupled with existing U-Pb dates, the postglacial Re-Os date of 662.4 ± 3.9 Mya represents direct geochronological constraints for both the onset and demise of a Cryogenian glaciation from the same continental margin and suggests a 55-My duration of the Sturtian glacial epoch. The Os and Sr isotope data allow us to assess the relative weathering input of old radiogenic crust and more juvenile, mantle-derived substrate. The preglacial isotopic signals are consistent with an enhanced contribution of juvenile material to the oceans and glacial initiation through enhanced global weatherability. In contrast, postglacial strata feature radiogenic Os and Sr isotope compositions indicative of extensive glacial scouring of the continents and intense silicate weathering in a post–Snowball Earth hothouse.

Item Type:Article
Keywords:Rhenium-osmium geochronology, Strontium isotopes, Osmium isotopes, Windermere Supergroup Neoproterozoic glaciation.
Full text:(AM) Accepted Manuscript
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Date accepted:08 November 2013
Date deposited:19 February 2015
Date of first online publication:16 December 2013
Date first made open access:19 February 2015

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