Paired δ13Ccarb-δ13Corg Evolution of the Dengying Formation from Northeastern Guizhou and Implications for Stratigraphic Correlation and the Late Ediacaran Carbon Cycle

Abstract

This study provides δ13C profiles from a lower-slope (Well ZK102) to basin (Bahuang Section) environment to better understand the temporal and spatial variability in δ13Ccarb-δ13Corg of the Yangtze Block during the Late Ediacaran. Our new δ13C profiles together with the reported data suggest that the Upper Ediacaran successions from different depositional environments are generally bounded by negative δ13Ccarb and/or δ13Corg excursions in the underlying and overlying strata. Moreover, the Upper Ediacaran δ13Ccarb profiles generally can be subdivided into two positive excursions and an interjacent negative excursion, whereas the paired δ13Corg profiles from different depositional environments have individual variation trends. On the other hand, these data show a large surface-to-deep water δ13C gradient (~5‰ variation in δ13Ccarb, >10‰ variation in δ13Corg) which can be reasonably explained by the heterogeneity of the biological activities in the redox-stratified water column. Furthermore, the decoupled δ13Ccarb-δ13Corg pattern with large δ13Corg perturbations at the lower slope precluded the existence of a large dissolved organic carbon reservoir at the Yangtze Block during the Late Ediacaran. Thus, the high δ13Ccarb values in the Upper Ediacaran succession could be balanced by large amounts of buried organic carbon likely associated with high productivity.