Two-billion-year-old evaporites capture Earth's great oxidation
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Major changes in atmospheric and ocean chemistry occurred in the Paleoproterozoic Era (2.5–1.6 billion years ago). Increasing oxidation dramatically changed Earth’s surface, but few quantitative constraints exist on this important transition. This study describes the sedimentology, mineralogy, and geochemistry of a remarkably preserved two-billion-year-old and ~800 meter-thick evaporite succession from the Onega Basin in Russian Karelia. The deposit consists of a basal unit dominated by halite (~100 m) followed by anhydrite-magnesite (~500 m) and dolomite-magnesite (~200 m) dominated units. The evaporite minerals provide a robust constraint that marine sulfate concentrations were at least 10 mmol/kg, representing an oxidant reservoir equivalent to over 20% of the modern ocean-atmosphere oxidizing capacity. These results show that substantial amounts of surface oxidant accumulated during this critical transition in Earth’s oxygenation.
Blättler , C , Claire , M , Prave , A R , Zerkle , A L & Warke , M R 2018 , ' Two-billion-year-old evaporites capture Earth's great oxidation ' Science . DOI: 10.1126/science.aar2687
© 2018 he Author(s). This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1126/science.aar2687
DescriptionFunding sources: Simons Foundation (SCOL 339006 to C.L.B.), European Research Council (ERC Horizon 2020 grant 678812 to M.C.), Research Council of Norway (RCN Centres of Excellence funding scheme project 223259 to K.P. and A.L.), Estonian Science Agency (PUT696 to K.K., A.L., K.P., T.K.).
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