Late Pleistocene-Holocene sedimentary facies and depositional environment of the eastern Gunsan Basin, mid-eastern Yellow Sea: Sequence stratigraphy in response to postglacial sea-level rise

Abstract

The sedimentary characteristics and depositional history of the post-glacial sedimentation in the eastern Yellow Sea were investigated using high-resolution subbottom profiles and sediment core data. Six-piston cores were drilled, and a multi-proxy analysis also was carried out on the sediment sequence, including sedimentological, high-resolution geochemical (ITRAX-XRF scanning), and accelerator mass spectrometry (AMS) analysis. The results show that the shelf sequence consists of 4 sedimentary units formed since the LGM: deltaic sand deposit (SU1), estuarine mud deposit (SU2), tidal ridge (SU3), and deltaic mud deposit (SU4). During the last glacial maximum, the eastern Yellow Sea was entirely exposed, and pre-Holocene deposits were incised. The incised channels were filled with deltaic and estuarine deposits, separated by a significant hiatus from the overlying transgressive deposits. During the transgression, coastal erosion and tidal reworking formed transgressive lag deposits and tidal ridges in the nearshore area. As the rate of sea-level rise decreased, large amounts of mud derived from the Huanghe River were transported to the central Yellow Sea, forming thin deltaic mud patches during the highstand stage. These subdivided sedimentary units are well correlated with the geochemical logging data. Sediment grain size and terrigenous input-based proxies such as Si/Ti, Ti/Ca, Zr/Rb, and Ca/Fe show distinctly the most significant value at the interval of deltaic deposit and tidal sand ridge. However, these output proxies are poorer in the uppermost deltaic mud succession. The sedimentary stratigraphic analysis applying this geochemical elemental analysis can be used as a proxy to infer the paleoenvironment in complex depositional environments such as the Yellow Sea. This study will contribute to research to establish the accurate stratigraphy of late Quaternary deposits and the precise reconstructions of paleoclimatic and paleoceanography.