Paired δ¹³C_carb-δ¹³C_org 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 δ¹³C_carb-δ¹³C_org 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 δ¹³C_carb and/or δ¹³C_org excursions in the underlying and overlying strata. Moreover, the Upper Ediacaran δ¹³C_carb profiles generally can be subdivided into two positive excursions and an interjacent negative excursion, whereas the paired δ¹³C_org 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 δ¹³C_carb, >10‰ variation in δ¹³C_org) which can be reasonably explained by the heterogeneity of the biological activities in the redox-stratified water column. Furthermore, the decoupled δ¹³C_carb-δ¹³C_org pattern with large δ¹³C_org 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 δ¹³C_carb values in the Upper Ediacaran succession could be balanced by large amounts of buried organic carbon likely associated with high productivity.

Keywords

Yangtze Block / Late Ediacaran / Dengying Formation / paired δ¹³C_carb-δ¹³C_org / stratigraphic correlation / carbon cycle

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