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

Early Palaeoproterozoic (2.5ĝ€"2.0 billion years ago) was a critical phase in Earth's history, characterized by multiple severe glaciations and a rise in atmospheric O 2 (the Great Oxidation Event). Although glaciations occurred at the time of O 2 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 187 Os/ 188 Os values in a sandstoneĝ€"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 O 2 levels became sufficiently high to deliver radiogenic continental Os to shallow-marine environments, indicating the synchronicity of an episode of increasing O 2 and deglaciation. This result supports the hypothesis that climatic recovery from the glaciations acted to accelerate the Great Oxidation Event.