Episode of intense chemical weathering during the termination of the 635 Ma Marinoan glaciation

Abstract

Significance At least two extreme glaciations (dubbed as snowball Earth events), each lasting millions of years and affecting the entire globe, occurred during the Cryogenian Period (∼720–635 Ma). These glaciations are recorded by globally distributed glacial deposits overlain by cap carbonates. According to the snowball Earth hypothesis, cap carbonate deposition was driven by intense continental weathering during deglaciation, but geochemical evidence is lacking. Using Mg isotopes as a proxy, we reconstruct the history of chemical weathering during and following the terminal Cryogenian Marinoan glaciation in South China. Our data confirm an episode of strong chemical weathering during the termination of the 635-Ma Marinoan glaciation, but its climax occurred before cap carbonate deposition.