Volcanism driven shift in the Mesoproterozoic carbon cycle and oxygen dynamics

Volcanism at ~1.4 Ga profoundly impacted Earth’s environment, yet its role in biogeochemical cycles remains debated. Here we integrate carbon and mercury isotopes, chemical index of alteration, machine learning-driven mercury flux reconstructions, and a multi-box biogeochemical model to reveal multiple volcanic imprints across Mesoproterozoic strata in North China Craton. Distinct mercury anomalies align with subaerial volcanism in Unit 3 and large igneous provinces in Unit 2 of the Xiamaling Formation, coinciding with photic zone euxinia. Machine learning models detect synchronous mercury perturbations in North China and North Australia, confirming the global influence of large igneous provinces. Sustained volcanic activity drives a carbon cycle transition from silicate weathering to biogenic carbon sequestration, marked by enhanced physical erosion, decoupling of inorganic and organic carbon isotopes, increased surface oxygenation, and intensified deep-ocean anoxia. The biogeochemical model captures the intrinsic links between multiple volcanic events, pulsed oxygenation, and carbon-sulfur-oxygen-mercury perturbations, confirming volcanism as a trigger for Mesoproterozoic oxygenation and early eukaryotic evolution. Large igneous provinces likely restructured carbon sequestration pathways in the Mesoproterozoic, shifting the balance between organic and inorganic carbon burial and contributing to changes in redox conditions and possibly supporting early eukaryotic development, according to mercury isotope records from the North China Craton, machine learning-driven mercury flux reconstructions, and biogeochemical models.