Paired δ^13Ccarb-δ^13Corg Evolution of the Dengying Formation from Northeastern Guizhou and Implications for Stratigraphic Correlation and the Late Ediacaran Carbon Cycle

This study provides δ^13C profiles from a lower-slope(Well ZK102)to basin(Bahuang Section)environment to better understand the temporal and spatial variability in δ^13Ccarb-δ^13Corg of the Yangtze Block during the Late Ediacaran.Our new δ^13C profiles together with the reported data suggest that the Upper Ediacaran successions from different depositional environments are generally bounded by negative δ^13Ccarb and/or δ^13Corg excursions in the underlying and overlying strata.Moreover,the Upper Ediacaran δ^13Ccarb profiles generally can be subdivided into two positive excursions and an interjacent negative excursion,whereas the paired δ^13Corg profiles from different depositional environments have individual variation trends.On the other hand,these data show a large surface-to-deep waterδ^13C gradient(~5‰variation in δ^13Ccarb,>10‰variation in δ^13Corg)which can be reasonably explained by the heterogeneity of the biological activities in the redox-stratified water column.Furthermore,the decoupled δ^13Ccarb-δ^13Corg pattern with large δ^13Corg 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 δ^13Ccarb values in the Upper Ediacaran succession could be balanced by large amounts of buried organic carbon likely associated with high productivity.