Precession-driven variations in phosphorus cycling facilitated Earth's oxygenation in the early Proterozoic

Abstract

Oxygenic photosynthesis in the ocean of the early Proterozoic may have been limited by the nutrient phosphorus. If so, precession-driven variations in riverine phosphorus input may have enhanced oxygenic photosynthesis and thereby contributed to the rise of atmospheric oxygen. Here, we combine geochemical analyses of 2.46-billion-year-old deposits of the Joffre Member of the Brockman Iron Formation (Australia) and results of a reactive transport model to reconstruct pathways of organic matter degradation and phosphorus cycling in oceanic sediments over a precession cycle. Our results support a conceptual model in which increased phosphorus availability during precession maxima at southern paleolatitudes drove net oxygen production by inducing increased reductant burial in the sediment (mainly as pyrite, vivianite and magnetite). During precession minima, legacy benthic release of methane may have enhanced photolysis of atmospheric methane, thereby allowing for additional net oxygen production. Hence, precession-driven variations in coupled carbon–phosphorus–oxygen cycling may have acted as an accelerator towards the Great Oxidation Event.