Textures, provenances and structures of sediment in the inner shelf south of Shandong Peninsula, western South Yellow Sea

Abstract

Although many studies have been performed on the mud wedge in the distal part of the Yellow River subaqueous delta, little is known about the southwestern terminus of the Yellow River mud wedge in the inner shelf of the Southern Yellow Sea (SYS). We use ∼3000 km of high-resolution subbottom seismic profiles, 147 surficial sediment samples, as well as 30 fluvial sediment samples to study sediment textures, provenance and structures in the inner shelf in western SYS. Our results show that sediment in the inner shelf south of Shandong Peninsula can be categorized into multiple types, including sand, silt, sandy silt, muddy sand, mud, gravel mud and others. About 60% of the study area is covered by silt and sandy silt. Assuming a finer texture of sediment from Yellow River and a relatively coarser one for sediment from local small rivers, our results reveal at least two contrasting sediment sources. East of the Laoshantou Headland, on the southern coast of the peninsula, the sediment is mainly from the Yellow River. Holocene sediment deposition reaches about 15 m thickness in water depths of ∼10 m. The homogeneous surficial sediment pattern is mainly controlled by the Yellow Sea Coastal Current, the Yellow Sea Warm Current, as well as local currents. However, west of Laoshantou Headland, sediment from local small rivers draining the peninsula plays a more important role. Over there the Holocene mud wedge is no more than 5-m thick, and is re-worked by strong tides and longshore currents. The seaward extension of Laoshantou Headland the southern peninsula seems to act as an effective sediment trap, aiding the accumulation of sediment carried by longshore currents. This new study delineates the western boundary of Yellow River subaqueous delta and helps better quantify sediment budget in the Yellow Sea. It also shed light on the sedimentation interplay of large rivers with local small rivers on many epicontinental shelves and passive margins around the world.