On the negative carbon isotope excursion across the Wuchiapingian–Changhsingian transition: A regional event in the lower Yangtze region, South China?

Previous studies have reported faunal changeover and carbon isotope excursions through the Wuchiapingian–Changhsingian (WC) transition, a geologically significant period of time that bridged two major extinction events: the end-Permian and Guadalupian–Lopingian boundary mass extinctions. However, the causes of the carbon isotope excursion across the WC interval remain poorly understood. This study presents sedimentological and geochemical data from three well-exposed sections in the lower Yangtze region, South China. A strong negative carbon isotope excursion in organic matter is recorded across the WC interval and correlates well with other sections in South China. Sedimentology and elemental geochemistry indicate that the lower Yangtze region experienced a distinct regional deepening during the WC transition inducing bottom water redox changes increased primary productivity. Possible causes of the negative carbon isotope excursion at the WC boundary include selective preservation of organic matter during early diagenesis under anoxic/euxinic conditions and changes in terrigenous organic matter input. Both of these factors were controlled by regional relative sea-level rise triggered by contemporaneous tectonic movements.