Grain-Size Distribution of Surface Sediments of Two Typical Headland Bay Beaches on Western Liaodong Bay, Bohai Sea and Simply Analysis of Hydrodynamic Conditions

Key words: 
• headland-bay beaches /
• grain-size parameter /
• coastal geomorphology /
• hydrodynamic conditions /
• Liaodong Bay

Abstract: Morphology, sediment components and grain-size parameters revealed the depositional environment of coastal zone, especially the beach unit. Measurements had carried out in Longwan Beach and the First Beach of Xingcheng City, Huludao City, Liaoning Province from July 2010 to December 2011. That is to say, four researches had been taken in every summer and winter, which included the observations and analysis of both beach elevations and sedimentary grain size characteristics. It was shown that ①by using 1985 Yellow Sea Elevation -0.6m and -4.7 m as boundaries, the two beaches in the study area might be, respectively, divided into three geomorphic units named beach unit, underwater slope unit and continental shelf unit. ②The sedimentary settings of Longwan Beach were stable, while the beach unit and underwater slope unit in the First Beach of Xingcheng City were alluvial, which might be caused by the engineering of beach nourishment. ③The two beaches might be divided into four sedimentary zones through the transverse variations of sediment components and grain size parameters. The changing trends of median diameter didn’t show transverse decreasing trend, while the variation rules of other gain size parameters were complicated in different sedimentary areas, indicating that the hydrodynamic conditions of each sedimentary zone were different. ④Compared to the First Beach of Xingcheng City, the sediments sampled in the sedimentary area I on Longwan Beach were thicker and worse sorted. the underwater slope unit of Longwan Beach was formed in a weak dynamic condition while the continental shelf unit of the First Beach of Xingcheng City was dominated by strong tidal currents.