DETRITAL ZIRCON GEOCHRONOLOGY OF THE SOUTHEASTERN YELLOW SEA SEDIMENTS AND IMPLICATION FOR THEIR PROVENANCES

U-Pb ages of 510 detrital zircons were analyzed using LA-ICPMS to constrain the provenance of coarse-grained sandy sediments deposited around the Jeju Island in the southeastern Yellow Sea. Ages of these zircons comprise three age groups: Mesozoic (100-200 Ma), Precambrian-Paleozoic (400-800 Ma) and Paleoproterozoic (1500-2600 Ma) groups. The Mesozoic age peak is predominant in all sites in the absence of Precambrian-Paleozoic zircons to the east of the Jeju Island and the scarcity of Paleoproterozoic zircon grains to its west. There is a distinctive reducing trend of the Paleoproterozoic age group with increasing Precambrian-Paleozoic zircons westwards. Comparison of these results with detrital zircon U-Pb age distributions of the Chinese and Korean river sediments flowing into the Yellow Sea, suggests that the Paleoproterozoic rocks, commonly distributed in the Korean Peninsula, probably supplied detritus to the east of the Jeju Island, whereas the scarcity of Precambrian-Paleozoic granitic bodies in the peninsula indicate their possible sources to be the North and/or South China cratons. Because the present Yellow and Yangtze rivers dominantly transport fine-grained sediments to the Yellow Sea, these sandy deposits are interpreted to be relict sediments deposited when the sea level fell down during the Last Glacial Maximum. Hence, the southeastern part of the Yellow Sea might have been the conflux of the extended rivers from China blocks and Korean Peninsula, and gradual westward change of zircon age distribution among the samples suggests reworking of these sediments during the postglacial transgression.