Fluctuations of continental chemical weathering control primary productivity and redox conditions during the Earliest Cambrian

The Ediacaran - Cambrian transition witnessed dramatic changes in the marine environment that are thought to have strongly influenced biological evolution. Previous studies have linked biological innovations to palaeo-redox changes and suggested that increased productivity is the primary driver of the marine environment. However, the primary productivity and redox control mechanism still need to be clarified. Here, we present new organic carbon isotopes, total organic carbon contents, major elements, and trace and rare earth elements in drill-core ZK107 from South China to reveal the continental chemical weathering, primary productivity, and redox control mechanism during the Earliest Cambrian (E-C). Our studies have shown intense continental weathering, and primary productivity fluctuations that were supported by weathering (CIA, Rb/Al) and productivity (Ba-bio, P) indicators. Additionally, the quantitative reconstructed productivity proxies (PP18, PP21, PP23) indicate a high primary productivity level in the E-C ocean, surpassing that of the modern oceans. The strengthening of continental weathering mainly causes high primary productivity because it can alter the nutrient supply to the oceans. We suggest that changes in primary productivity closely associated with continental weathering are the leading cause of marine anoxia during the E-C. This study establish a linkage between the land and marine system during the E-C, confirming the terrestrial controls on the marine chemical changes and providing new insights into understanding the evolution of the Earth's surface changes during the Ediacaran - Cambrian transition.