Trace element and mineral composition of Ediacaran-early Cambrian strata in South China and their geochemical implications

Abstract Ediacaran-early Cambrian is a critical interval in the evolution of atmosphere-ocean environment and biodiversity. The continuous Ediacaran-Cambrian strata in South China provide a good opportunity for investigating the associated environment with its ecological evolution. In this study, outcrop sedimentary rock samples collected from the Dongkanshang and Fengtan sections on the Yangtze Block were analyzed for their mineral and trace element compositions. The results showed some heterogeneity in the geochemistry of the Ediacaran-early Cambrian ocean in South China. Based on the U/Th, V/(V+Ni), V/Cr, and Ni/Co ratios, the middle-deep water was predominated by anoxic or euxinic condition with interferences from several transient oxidation events. The basinal Fengtan section indicates a more reduced depositional environment when compared with the slope Dongkanshang section. This shows that the seawater oxygenation was a gradual process that expanded from shallow to deep water.