Organic Carbon Deposition on the Inner Shelf of the East China Sea Constrained by Sea Level and Climatic Changes Since the Last Deglaciation

The East China Sea (ECS), which is located in the transitional zone between land and ocean, is the main site for the burial of sedimentary organic carbon. Despite good constraints of the modern source to the sinking process of organic carbon, its fate in response to changes in climate and sea level since the last deglaciation remains poorly understood. We aim to fill this gap by presenting a high-resolution sedimentary record of core EC2005 to derive a better understanding of the evolution of the depositional environment and its control on the organic deposition since 17.3 kyr. Our results suggest that sedimentary organic carbon was deposited in a terrestrial environment before the seawater reached the study area around 13.1 kyr. This significant transition from a terrestrial environment to a marine environment is reflected by the decrease in TOC/TN and TOC/TS ratios, which is attributed to deglacial sea level rise. The sea level continued to rise until it reached its highstand at approximately 7.3 kyr when the mud depocenter was developed. Our results further indicate that the deposition of the sedimentary organic carbon could respond quickly to abrupt cold events, including the Heinrich stadial 1 and the Younger Dryas during the last deglaciation, as well as 'Bond events' during the Holocene. We propose that the rapid response of the organic deposition to those cold events in the northern hemisphere is linked to the East Asian winter monsoon. These new findings demonstrate that organic carbon deposition and burial on the inner shelf could effectively document sea level and climatic changes.