Weathering the Snowball: Insights and Implications from Re-Os geochronology

Monday April 22 at 2 p.m.
Nordensköldsalen, level 3, Geovetenskapens hus
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by Professor Alan D. Rooney
Department of Earth and Planetary Sciences, Harvard University

 link to Prof. Alan D. rooney's page 

 

Weathering the Snowball: Insights and Implications from Re-Os geochronology

The Neoproterozoic Era (1000–542 Ma) witnessed a series of unique geological and biogeochemical events that critically shaped the evolution of life. After nearly a billion years with no evidence for glaciation, between 717 and 635 Ma ice advanced to equatorial latitudes at least twice. Although the initiation mechanism of these Neoproterozoic “Snowball Earth” events has remained a mystery, the rough synchroneity of rifting of the supercontinent Rodinia, the emplacement of large igneous provinces, and the onset of the Sturtian glaciation has suggested a tectonic forcing. The lack of age constraints from a single glaciogenic succession has hampered attempts to constrain the duration of these glaciations and correlate global Neoproterozoic strata. New precise rhenium-osmium (Re-Os) geochronology data from Sturtian-age glacial deposits in northwestern Canada confirms that the Sturtian glaciation(s) were long lasting and deglaciation was globally synchronous. Highresolution Os and Sr isotope profiles that bracket glaciogenic strata provide novel insights into weathering regimes in a pre- and post-Snowball environment. These data highlight the potential for Re-Os geochronology to help refine the temporal framework of Neoproterozoic geochemical, tectonic and evolutionary upheavals.

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