Minor Δ33S anomalies coincide with biotic turnover events during the Great Ordovician Biodiversification Event (GOBE) in South China

In this study, we report multiple S-isotopic data (delta S-34 and Delta S-33) of sedimentary pyrite in Early to Late Ordovician sections from South China. The results reveal two distinct groups of negative Delta S-33 anomalies during the Dapingian and Sandbian to Early Katian stages, which coincide with two faunal turnover events. The negative Delta S-33 values reflect the mixing of sulfides with strongly negative delta S-34 and positive Delta S-33, and sulfide with strongly positive delta S-34 and positive. Delta S-33. This mixing scenario may have resulted from the impinging of deep anoxic waters onto the continental shelves possibly facilitated by sea-level rise. The temporal co-occurrence of negative Delta S-33 anomalies with intervals of faunal turnover in brachiopod assemblages of South China suggests that the encroachment of anoxic waters may have driven the diversity crises. Our results provide evidence for a dynamic mechanism linking the recurrent upwelling of deep anoxic waters and faunal turnovers during the Early to Late Ordovician.