Earth’s Great Oxidation Event facilitated by the rise of sedimentary phosphorus recycling

The rise of atmospheric oxygen during the Great Oxidation Event some 2.4 billion years ago was a defining transition in the evolution of global biogeochemical cycles and life on Earth. However, mild oxidative continental weathering and the development of ocean oxygen oases occurred several hundred million years before the Great Oxidation Event. The Great Oxidation Event thus represents a tipping point, whereby primary productivity and O2 production overwhelmed the input of reduced species that consume O2, and its timing is determined by the input of phosphate, the major limiting nutrient, and the dynamics of the solid Earth. Here, we determine the phase partitioning of phosphorus in 2.65 to 2.43 billion year old drill core samples from the Transvaal Supergroup, South Africa, to investigate the sequence of events that facilitated persistent atmospheric oxygenation. On the basis of the elevated C/P ratios found within sulfidic sediments, relative to the Redfield ratio, we suggest that, as oxidative continental weathering increased the influx of dissolved sulfate and hence dissolved sulfide in the oceans, bioavailable phosphorus became more abundant due to anoxic recycling of sedimentary phosphorus phases. Biogeochemical modelling indicates that this initiated a positive feedback on primary productivity and shows that the evolution of phosphorus recycling may have been a critical step that enabled Earth’s transition to a persistently oxygenated atmosphere.