The characteristics of topography and surface sediment distributionnear Heishi Island, Shandong Peninsula

The sea areas near Heishi Island are located in the east of Heini Bay, Weihai, Shandong Peninsular, East China. The sedimentary environment is complex and variable, and many factors control the distribution of surface sediments, forming a variety of developmental and evolutionary patterns. A comprehensive geological environment survey of the study area was carried out in Sep.–Nov., 2021 by using acoustic detection, surface sediment sampling, ocean current observation, laboratory sediment grain size testing, and comprehensive interpretation of data, based on which the characteristics of water depth topography, sub-bottom profile structure, and surface sediment distribution in the study area were analyzed and the controlling factors and causes of sediment distribution in the area were revealed from multiple perspectives. Results show that the water depth of the target area was between 3 m and 24 m, on average of about 14 m, shallower in the west and deeper in the east in a steep slope. With the increase of water depth, the slope gradually decreased, and the main landform type was underwater erosion bank slope. The acoustic reflection interface of seabed sub-bottom profile was clear and co be tracked globally. The siltation thickness was 0.5–2 m, and the thickness of sediment layer varied from east to west but relatively stable. The types of surface sediments varied, forming zones around the island, including silty sand, gravel, and muddy gravel away from the island. From west to east, the grain size of surface sediments decreased gradually and the sorting became better. It is concluded that the distribution of surface sediments in the study area is affected by regional topography and hydrodynamic conditions.