Provenance change of fine-grained sediments in the South West Cheju Island Mud (SWCIM) since the last glacial period

초록

The records of changes in sediment provenance have been importantly used for sea level variation. The South West Cheju Island Mud (SWCIM), located at the northern end of the East China Sea, has been attracting attention from many researches because it probably records the provenance change according to sea level change. However, the sediment provenance and changes in the provenance due to sea level rise remain unclear. In this study, we traced the provenance change due to sea level rise after the last glacial period using rare earth elements and clay mineral composition for three cores for which data of grain size and dating are known. Unit 3, which is the last glacial period, was characterized by a high silt content and S/I (Smectite/Illite) ratio, and most of the sediments were sourced directly from the paleo Huanghe. However, some of Unit 3 sediments with relatively high total rare earth content are believed to originated from the Korean rivers. Unit 2, which corresponds to the transgressive period, exhibited an abundance of sand due to the tidal stress stronger than the present, and during this period the sediment provenance changed from the Huanghe to the Changjiang. Unit 1 corresponds to highstand period when sea level and oceanic circulation similar to the present is established. Unit 1 sediments have a characteristic of typical mud patch with low sand and high clay contents, and the sediment provenance was identified as Changjiang. The Changjiang sediments are believed to be supplied to the study area through the Changjiang Diluted Water or Yellow Sea Warm Current Therefore, the fine sediment provenance in the SWCIM changes in the order of the Huanghe origin, the multi-origin of the Huanghe and Changjiang, and the Changjiang origin according to sea level change.

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