The sedimentary characteristics and sediment transport in the tidal depositional system of the Eastern Bohai Sea

The Laotieshan Channel is one of the major channels in the north of the Bohai Strait, China. A tidal depositional system shaped by strong currents has developed in the eastern Bohai Sea, consisting of the Laotieshan Channel, the Liaodong Shoal and the Bozhong Shoal. Based on the grain-size characteristics, distribution of heavy minerals and numerical simulation results, the sediment distributions of different geomorphic units were analysed, and the trend of sediment transport is discussed. The results show that coarse-grained sediment is mainly distributed in the Laotieshan Channel, and the typical sediment type is muddy sandy gravel, whereas fine-grained sediment mainly covers the Liaodong Shoal and the Bozhong Shoal. Moreover, the sediments in sand ridges have a finer grain size than those in troughs. The sediment of the Bozhong Shoal mainly consists of muddy sand. The sediments of ridges, in contrast, are sand and silty sand; those of troughs are sandy silt and silty sand. The distribution of typical heavy minerals is similar to that of total heavy minerals and areas with relatively high content occur in the sand ridge area and the sand sheet area. The Laotieshan Channel is eroded and the sediment is transported to the Liaodong Shoal and the Bozhong Shoal. The sediment continues to be transported northwest in the Bozhong Shoal, while in the Liaodong Shoal it is transported approximately along the long axes of sand ridges. The sediment transport trends in the tidal depositional system are adapted to the hydrodynamic environment, and the tidal geomorphological system of the Liaodong Shoal will remain stable at the century scale.