A Comprehensive Investigation of Coastal and Shelf Sediment Sources in the South Sea of Korea: A Marginal Sea of the Northwestern Pacific

Abstract

To identify and quantify the sediment sources in the South Sea of Korea, a marginal sea of the northwestern Pacific, we analyzed a comprehensive aluminum–magnesium dataset comprising 121 surface sediment samples and two sediment cores. The findings demonstrate pronounced spatial variation in sediment sources, with Korean river sediments dominating in embayment bays and Chinese river sediments prevailing in the shelf area. In the coastal zone, Korean river sediments account for over 60–70%, but their proportion decreased to 10–20% in the shelf zone. This reveals that most of the sediments from Korean rivers are mainly confined to the coastal embayments, with limited transport to the shelf area. Notably, the central South Sea mud (CSSM) deposits are primarily govern by the sediment influx from Chinese rivers (CR), rather than the Seomjin River discharge. The prevalence of CR-sourced sediments in the shelf region is closely linked to the Tsushima Warm Current and Cheju Warm Current, transporting sediments from the East China Sea shelf northwards and the southwestern Korean coastal zone eastwards, respectively. This driving mechanism for the widespread deposition of CR sediments is further supported by an abrupt shift from KR to CR dominance in sediment sources around 8 kyr BP, coinciding with the establishment of the modern current systems in the northwestern Pacific marginal seas. Our study provides a new perspective on the source-to-sink pathways, particularly of Chinese river sediments, in the formation of the Korean coastal mud deposits.