PALEOENVIRONMENTAL CHANGES IN THE KOREA STRAIT DURING THE POST-GLACIAL MARINE TRANSGRESSION

A 31m-long sediment core (SSDP-102) was taken from the inner shelf (about 40m water-depth) off the northwestern coast of the Korea Strait. Detailed organic-geochemical analyses and stable oxygen isotope measurements on planktonic and benthic foraminifers were performed to establish a high-resolution stratigraphy in the Korea Strait and to elucidate the paleoenvironmental changes associated with the Post-glacial marine transgression. The high-resolution stratigraphic framework of the core was primarily established using 11 AMS 14C ages. The sedimentary sequences of the core SSDP-102 well record the paleoenvironmental changes in transition interval of sea- level rise during the last 12.1 cal ka BP. According to the high-resolution seismic reflection profiles, lithofacies, organic-geochemical data, and d18O and d13C records, the core SSDP-102 can be divided into three units (lll to l in ascending order) above the acoustic basement, which reflect distinct changes of depositional environments in response to the Post-glacial marine transgression. Therefore, it is suggested that three phases of sea-level change have taken place within the inner shelf of the Korea Strait following the Post-glacial marine transgression; (1) brackish-estuarine environments from ca. 12.1 to 6.2 cal ka BP; (2) near-shore environments with a period of decreased rising of sea level between 6.2 and 5.1 cal ka BP; (3) modern marine environments after 5.1 cal ka BP. In particular, the occurrence of palnktonic foraminifers G. rubber and N. dutertrei, and their d18O and d13C records together with d13Corg values imply that the present marine conditions influenced by the warm Tsushima Current may have been gradually established after ca. 4.5 cal ka BP.