383 / 2024-09-15 21:33:36

Disentangle catchment weathering and river sediment provenance signals in East Asian continental margins

Continental margin, silicate weathering, source-to-sink process, river, East Asia

East Asia continental margin is featured by the tremendous input of terrestrial materials from surrounding landmasses as it bridges the largest Euroasian continent and largest Pacific. Two major types of fluvial sediment routing systems account for active river sediment source-to-sink transport processes, which include the mega-rivers in Eurasian continent such as the Changjiang (Yangtze) River, and the small mountainous rivers in Taiwan Island and SE China, e.g. the Zhuoshui River and Mulanxi River. Among which, the small mountainous rivers are relatively less investigated although they play a disproportionate role in sediment discharge and greatly influence the terrestrial material cycle in the West Pacific. Here, we present the data of multiple geochemical and isotopic proxies (Nd, Li) to trace the silicate weathering and sediment source-to-sink processes in the large river systems and small mountainous catchments (Zhuoshui and Mulanxi Rivers) in the East Asian continental margin, and particularly the weathering mechanisms and environmental signal propagation in the catchments will be discussed. We observed the conservative behaviour of dissolved Li during the mixing processes of Changjiang Estuary, while the particulate forms display fractionations. The small dynamic mountains rivers in Taiwan exhibit large sedimentary geochemical and provenance heterogeneity despite their fast sediment transfer from land to sea, which limits the silicate weathering intensity. Comparatively, the transport-limited weathering regime is observed in the small river basins in SE China and the river sediment source-to-sink processes are greatly influenced by strong tide in the estuaries. Our study provides more constraints on the earth surface processes in East Asia continental margin.