Osmium evidence for synchronicity between a rise in atmospheric oxygen and Palaeoproterozoic deglaciation

摘要

Early Palaeoproterozoic (2.5–2.0 billion years ago) was a critical phase in Earth's history, characterized by multiple severe glaciations and a rise in atmospheric O₂ (the Great Oxidation Event). Although glaciations occurred at the time of O₂ increase, the relationship between climatic and atmospheric transitions remains poorly understood. Here we report high concentrations of the redox-sensitive element Os with high initial 187Os/188Os values in a sandstone–siltstone interval that spans the transition from glacial diamictite to overlying carbonate in the Huronian Supergroup, Canada. Together with the results of Re, Mo and S analyses of the sediments, we suggest that immediately after the second Palaeoproterozoic glaciation, atmospheric O₂ levels became sufficiently high to deliver radiogenic continental Os to shallow-marine environments, indicating the synchronicity of an episode of increasing O₂ and deglaciation. This result supports the hypothesis that climatic recovery from the glaciations acted to accelerate the Great Oxidation Event.. ? 2011 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.