Continental weathering controlled marine carbon-sulfur cycles during the Carnian Pluvial Event (Late Triassic) in the Nanpanjiang Basin, South China

The Carnian Pluvial Event (CPE) was a key Late Triassic crisis of global warming, intensified hydrology, and marine ecological disruption. Although extreme continental weathering characterized this period, its connections to marine redox and biogeochemical cycles remain unclear. This study presents carbonate carbon isotopes (δ¹³C_carb), carbonate-associated sulfate sulfur isotopes (δ³⁴S_CAS), and elemental data from a Carnian marine succession (Longchang section, South China). Redox proxies (Mo_EF-U_EF and Mo_EF*-U_EF*) indicate a shift from pre-CPE oxic conditions to widespread dysoxia-anoxia with intermittent euxinia during and after the CPE. Cd/Mo and Co×Mn suggest increased basin restriction and enhanced terrestrial-driven organic burial during the CPE. Our data reveal multiple negative carbon isotope excursions (NCIEs) coupled with extreme negative δ³⁴S_CAS excursions (to ~−10‰ to −20‰), documenting pulsed inputs of isotopically light carbon and sulfur from intensified continental weathering and possibly volcanism. Crucially, coupled δ¹³C_carb-δ³⁴S_CAS covariations highlight temporally evolving controls, in which early CPE phases (e.g., NCIE-2 and NCIE-3) were weathering-dominated, while later stages (i.e., following the NCIE-3) were influenced by pyrite-organic carbon co-burial linked to changes in marine productivity. These findings establish terrigenous fluxes as a key modulator of marine biogeochemistry during the CPE.