Erosional shelf ridges in the mid-eastern Yellow Sea

Abstract

In the mid-eastern Yellow Sea, closely spaced high-resolution seismic profiles and a 44-m-long sediment core (YSDP-104) were analyzed to reveal the internal structures and stratigraphy of the shelf ridges currently shaped by tidal currents. Three depositional sequences (sequences I, II and III in descending order) can be recognized. Sequence III, the substratum of the ridges, consists of coarse-grained sediments in the lower part (non-marine deposits) and tide-influenced muddy sediments in the upper part (probable transgressive to highstand systems tract). Sequence II represents internal ridge sediments, similar in character to sequence III, but is demarcated by an undulatory ridge topography. According to radiocarbon dating of marine muds, these sequences range in age from 47,000 to 28,000 years B.P., representing two cycles of short-term sea-level fluctuations during oxygen isotope stage 3. Sequence I consists mostly of late-Holocene transgressive sand veneer on the ridge surface. It also includes minor amounts of early-Holocene muddy sediments occasionally underlying the sand. Most of the ridges are presently undergoing erosion by tidal currents, forming widespread sand dunes on the entire surface.