Two-billion-year-old evaporites capture Earth's great oxidation

Funding 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.).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 robustly constraint marine sulfate concentrations to at least 10 millimoles per kilogram of water, 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.PostprintPeer reviewe

Two-billion-year-old evaporites capture Earth’s great oxidation

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 two-billion-year-old and ~800 m-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

The Sedimentary Geochemistry and Paleoenvironments Project.

Authors thank the donors of The American Chemical Society Petroleum Research Fund for partial support of SGP website development (61017-ND2). EAS is funded by National Science Foundation grant (NSF) EAR-1922966. BGS authors (JE, PW) publish with permission of the Executive Director of the British Geological Survey, UKRI.Publisher PDFPeer reviewe