The emergence of an aerobic world: isotopic evidence for biogeochemical changes at the Archean-Proterozoic transition

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Undoubtedly, the late Neoarchean and early Paleoproterozoic is a time window in Earth history, where our planet experienced a most extraordinary environmental change: the first major rise in atmospheric oxygen, likely changing existing biochemistries from anaerobic to aerobic. This point in time, termed the Great Oxidation Event, marks the onset of aerobic conditions in environments located at the Earth’s surface. Anaerobic processes vanished from the surface waters into still anoxic deep waters and/or into the sediment. Consequently, oceanic biochemistry progressively resembled that of the modern aerobic world, particular with respect to the recycling of organic matter. The rise in atmospheric oxygen was paralleled by an increase in oceanic sulphate abundance as a consequence of oxidative weathering on the continents. An increasing level of oceanic sulphate, in turn, must have stimulated its microbial turnover via sulphate reduction, with other forms of microbial sulphur cycling that likely followed. A detailed sulphur isotope record for this time interval will document this increasing importance of sulphur metabolism under changing environmental conditions.