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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. [ABSTRACT FROM AUTHOR]

Under the influence of glacial-interglacial climate change and regional tectonic activities in the Quaternary, the sedimentary environments of the Bohai Sea changed greatly, providing significant information on transgression-regression events, East Asian monsoon changes and regional tectonic activities. This study analyzed the sedimentological characteristics of the BH1302 core (water depth of 12.3 m, length of 70.2 m) in the southern Bohai Sea based on grain size, foraminiferal assemblages, carbon and oxygen isotopes in foraminiferal shells and element geochemistry, and established a chronological framework based on AMS 14C, optically stimulated luminescence dating and Oxcal age-depth model using Bayesian modeling. The results showed that three interglacial transgressions and one interstadial transgression were revealed in BH1302 since the late Quaternary, corresponding to marine isotope stages (MIS) 7, 5, 3 and 1, and three subinterglacial transgressions were further identified during MIS 7. The sedimentary environments of Laizhou Bay transitioned from an estuary environment dominated by rivers to a neritic environment dominated by marine conditions because of subsidence of the Miaodao uplift in late MIS 7.1. Three subinterstadial transgressions occurred in both MIS5 with two subinterstadial in MIS 3, and the highstand sea level of MIS 3 reached approximately −18 ∼ −21 m. Under the influence of sea level fluctuations and the East Asian monsoon, the sedimentary environments of MIS 1 can be divided into a low salinity tidal-flat environment (12.0–7.0 kyr BP), a low salinity neritic environment (7.0–4.5 kyr BP) and a modern neritic environment (∼4.5 kyr BP). • The isotopes in the foraminifera shells have good indications to the impact of freshwater input on the neritic environments. • Except for 4 interglacial transgressions, the paper further identifies 3 sub-interglacial transgressions in the MIS7 period. [ABSTRACT FROM AUTHOR]