Spatial variability of surface sediments on the eastern continental margin of Korea

Total 99 surface sediment samples were obtained from eastern continental margin of Korea from Uljin to Busan below water depth 500 m to investigate the spatial variability of surface sediments. Mean grain size (Mz) of surface sediments ranges from 1.74 to 9.70 Φ (mean of 6.19±2.28 Φ), fine-grained sediments were mainly deposited along the coastal line on the Korea Strait Shelf Mud (KSSM) and Hupo Basin, whereas, coarse-grained sediments were covered on the Hupo Bank and southern continental margin. TOC content of surface sediments ranges from 0.09 to 3.27% (mean of 1.36±0.83%) and spatial variation is similar with that of Mz. Spatial distribution patterns of Al (1.56~10.98 %), K (0.94~3.29%), Ti (0.04~0.37%), Ni (1.97~38.18 mg/kg), Co (1.28~14.31 mg/kg), Cs (0.78~10.47 mg/kg), and total REEs (39.11~173.80 mg/kg) were also similar with that of Mz (r > 0.70). Generally, contents of geochemical element were lower in coarse-grained sediments on the Hupo Bank and southern continental margin and relatively higher in fine-grained sediments on the KSSM and Hupo Basin. On the contrary, Ba (126.58~476.35 mg/kg) showed opposite pattern, high Ba contents were observed in coarse-grained sediments on the Hupo Bank and southern continental margin while, lower contents showed in fine-grained sediments. Surface sediments of the eastern continental margin of Korea could be divided into four types based on characteristics of geochemical element: Type I sediments were obtained from on the Hupo Bank and outer shelf/shelf break of the southern continental margin and might be composed with relic sediments formed during the Miocene and/or Last Glacial Maximum. Type II sediments were obtained from outer shelf of the southern continental margin especially beside of the Korea Trough and believed to be coarse-grained sediments deposited during the glacial age derived through the Korean Trough. Type III sediments which covered on the KSSM were mostly composed with fine-grained sediments. KSSM was deposited during the Last Glacial Maximum and consist of mixtures of sediments discharged from Chinese rivers and Nakdong River. Type IV sediments were mostly covered on the Hupo Basin. Sediments on the Hupo Basin were deposited during the Quaternary but sediment provenance should be differ from KSSM and it might be originated from small streams near the Hupo Basin.