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 (W-C) 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 W-C 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 W-C 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 W-C transition inducing bottom water redox changes increased primary productivity. Possible causes of the negative carbon isotope excursion at the W-C 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.