Pattern of δ13Ccarb and implications for geological events during the Permian-Triassic transition in South China

Data from five marine sections across the Permian-Triassic boundary in southern China reveal a pattern of C-13-depleted carbonate (delta C-13(carb)) in different facies spanning carbonate platform to lower slope. A gradual decrease of delta C-13(carb) is evident in all sections and matched by an opposing change in Sr-87/Sr-86 from the Late Permian to the Induan (Early Triassic). These complementary trends in strontium and carbon isotope data imply an extended period of enhanced continental uplift and weathering of silicates and organic matter across the Permian-Triassic event boundary (PTEB). A pronounced sharp drop of delta C-13(carb) at the PTEB is most recognizable in the upper ramp environment of Meishan, occurs weakly in shallow water environments and cannot be discerned in the deepest water setting. We propose that this pattern reflects an enhancement of stratified-ocean conditions in the immediate aftermath of the latest Permian transgression. The sharp drop in delta C-13(carb) at the PTEB in the platform ramp environments likely resulted from the depth-selective calcification of C-13-depleted dissolved inorganic carbon (DIC) formed by respiration of organic matter including, perhaps, methane. Indeed, massive volcanism at the PTEB would have enhanced eutrophication and stratification thereby slowing the mixing of C-13-depleted DIC into deeper-water environments. Copyright (C) 2010 John Wiley & Sons, Ltd.