Reverse weathering may amplify post-Snowball atmospheric carbon dioxide levels

Abstract Snowball Earth glaciations are the most extreme climate perturbations recorded in Earth’s history. It has been argued that the termination of these events was characterized by a single rapid transition from near-global ice coverage to an ice-free greenhouse climate state. Notably, this deviates with more extended transition periods of ice sheet waxing and waning typical of Phanerozoic glaciations. Using a coupled mineralogical and Mg and Li isotopic approach, we explore the role that authigenic clay formation within the seafloor may have played on Earth’s climate during deglaciation of the Marinoan Snowball Earth event. Marine authigenic clay formation—a process referred to as reverse weathering—recycles carbon within the ocean–atmosphere system and acts to elevate atmospheric CO2 levels. The results indicate a shift towards more extensive reverse weathering within the uppermost portion of the glaciogenic Nantuo Formation in South China. Carbon cycle modeling indicates that widespread reverse weathering could have driven a protracted (millions of years) carbon dioxide drawdown following high carbon dioxide levels expected during deglaciation.