Abstract

The Upper Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE, ca. 497 to 493 Ma) is characterized by a globally observed positive δ13C excursion of ∼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 δ13Ccarb and δ13Corg 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 δ13Ccarb and δ13Corg gradient, showing decreasing δ13C values with increasing water depth. The changes of δ13C in South China are in contrast to comparable facies-dependent δ13C data from the central Missouri (USA) intrashelf basin, which show increasing δ13C 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.

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