The impact of Holocene interactions among climate, ocean current, and shear front factors on fine sediment dispersal in the central South Yellow Sea

Abstract

The South Yellow Sea (SYS) is strongly influenced by large amounts of sediment input from surrounding rivers, but the dispersal patterns of these sediments, especially how they accumulate in the central Yellow Sea mud (CYSM) region, have not been well illustrated. Here, we present a detailed temporal variation record of the clay mineral compositions from core YSC-10 of the northern SYS near the western margin of the CYSM, trying to investigate sediment provenance and to discuss transport processes occurring during the Holocene. The clay mineral assemblages of core YSC-10 mainly consist predominantly of illite (68 ± 3%), followed by chlorite (15 ± 2%) and kaolinite (10 ± 2%), with scarce amounts of smectite (6 ± 3%). Combined with published data, our results suggest that the fine sediments of core YSC-10 are most likely a mixing product of the Huanghe (Yellow River), Changjiang (Yangtze River) and Korean Peninsula small river sediments, with notable temporal changes. During 8.4–6.4 ka, the Huanghe sediments from the Bohai Sea flowed directly into the SYS and played major roles in the sedimentation therein. In addition, as the modern ocean circulation pattern was formed ∼6 ka, the ocean front developed along the Shandong Peninsula coastal area of the SYS, which would have prevented the dispersal of the Huanghe sediments to the CYSM. The Changjiang sediments delivered by the diluted water replaced those from the Huanghe as the main source of the CYSM during the period of 6.4–4.2 ka. After 4.2 ka, the coastal shear front weakened and moved seawards due to the weakening and eastward shift of the Yellow Sea Warm Current (YSWC) in winter and the weakening and shrinking of the Yellow Sea Cold Water Mass (YSCWM) in summer. The Huanghe sediments seem to have increased and fluctuated frequently to core YSC-10 since then. Our study thus highlights that the coastal shear front may have played an important role in the source-to-sink processes of the SYS.