Isotopic Evidence for Massive Oxidation of Organic Matter Following the Great Oxidation Event

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Science  01 Dec 2011:
DOI: 10.1126/science.1213999


The stable isotope record of marine carbon indicates that the Proterozoic Eon began and ended with extreme fluctuations in the carbon cycle. In both the Paleoproterozoic [2500 to 1600 million years ago (Ma)] and Neoproterozoic (1000 to 542 Ma), extended intervals of anomalously high δ13C indicate high rates of organic matter burial and release of oxygen to the atmosphere; in the Neoproterozoic, the high δ13C interval was punctuated by abrupt swings to low δ13C, indicating massive oxidation of organic matter. We report a Paleoproterozoic negative δ13C excursion that is similar in magnitude and apparent duration to the Neoproterozoic anomaly. This “Shunga-Francevillian” anomaly may reflect intense oxidative weathering of rocks as the result of the initial establishment of an oxygen-rich atmosphere.