Two-billion-year-old evaporites capture Earths great oxidation

This study describes the sedimentology, mineralogy, and geochemistry of a 2-billion-year-old, ~800-meter-thick evaporite succession from the Onega Basin in Russian Karelia. The deposit consists of a basal unit dominated by halite (~100 meters) followed by units dominated by anhydrite-magnesite (~500 meters) and dolomite-magnesite (~200 meters). The evaporite minerals robustly constrain marine sulfate concentrations to at least 10 millimoles per kilogram of water, representing an oxidant reservoir equivalent to more than 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.

Source: ScienceNOW - April 19, 2018 Category: Science Authors: Blättler, C. L., Claire, M. W., Prave, A. R., Kirsimäe, K., Higgins, J. A., Medvedev, P. V., Romashkin, A. E., Rychanchik, D. V., Zerkle, A. L., Paiste, K., Kreitsmann, T., Millar, I. L., Hayles, J. A., Bao, H., Turchyn, A. V., Warke, M. R Tags: Geochemistry, Geophysics reports Source Type: news