中国科学院南京地质古生物研究所机构知识库

The Upper Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE, ca. 497 to 493 Ma) is characterized by a globally observed positive delta C-13 excursion of similar to 4% to 6%. Late Cambrian strata of South China, consisting of thick carbonate rocks with an excellent fossil record, provide key sedimentary successions for characterizing the SPICE and understanding its paleoenvironmental significance. Here we present high-resolution paired delta C-13 (carb) and delta C-13(org) data from three broadly regional late Cambrian (Furongian) sections that were deposited along a shelf margin-slope transect in South China. Our data exhibit an apparent paleobathymetry-dependent delta C-13(carb) and delta C-13(org) gradient, showing decreasing delta C-13 values with increasing water depth. The changes of delta C-13 in South China are in contrast to comparable facies-dependent delta C-13 data from the central Missouri (USA) intrashelf basin, which show increasing delta C-13 values with increasing water depth, but in a shallower paleoenvironmental system. The facies-dependent carbon-isotopic data from South China suggest enhanced burial rates of organic carbon, and may have important implications for understanding changes in paleo-redox conditions and their potential link to the mass extinction.