Volcanic forcing of oxygenation dynamics in the mid-Proterozoic

Large Igneous Province (LIP) volcanism is commonly considered to have driven ocean deoxygenation and associated mass extinctions during the Phanerozoic. However, the impacts and feedback mechanisms associated with LIP emplacement in the prevailingly low-oxygen Precambrian environment remain poorly understood. Here, we present mercury isotope, iron speciation and phosphorus phase partitioning data for mid-Mesoproterozoic marine sediments of the Shennongjia Group, South China, to reconstruct the response of the phosphorus cycle to LIP volcanism. Our data indicate that LIP volcanism triggered an expansion in marine euxinia, which enhanced phosphorus recycling and stimulated surface ocean primary production, thereby promoting increased burial of organic carbon and pyrite. This facilitated net marine oxygenation, with repeated volcanic pulses ultimately resulting in enhanced ventilation of the mid-Proterozoic ocean. We propose that while mid-Proterozoic LIP volcanism may have caused short-term ecological crises, the ensuing redox-nutrient feedbacks ultimately stimulated progressive oxygenation of Earth’s surface environment.