ABSTRACT
The grain size analysis of 21 surface sediment samples collected in 2019 in the offshore area of Tianjin shows that the surface layer of the seafloor in the study area is mainly clay silt deposits. Based on the cluster analysis of the surface sediment grain size parameters, and combined with the hydrodynamic conditions, the study area could be classified into three depositional environments: group I has large average grain size, high sand content, simple and strong hydrodynamic conditions. According to the location of the sampling point and the size of the grain, it can be divided into the intertidal environment(I-a), which is strongly influenced by rivers but weakly influenced by coastal currents, and intertidal-shallow marine environment (I-b), which is strongly influenced by currents but weakly influenced by rivers; Group II has the largest grain size which is mainly coarse powder silt, with strong hydrodynamic force and complex material sources. It can be speculated that it's a shallow marine sedimentary environment influenced by both rivers and currents; Group III has the finer grains, the transport mode is mainly with suspension, the hydrodynamic environment is stable and weak, indicating a single hydrodynamic force, so that it can be speculated that it's an intertidal-shallow marine sedimentary environment influenced by the seasonal intra-bay circulation.
