Paleo-geomorphology And Sedimentary Systems Of The Xiyang Tidal Channel On The Central Jiangsu Coast At The Late Pleistocene,southwestern Yellow Sea

The terrigenous sediments of the Yellow Sea continental shelf are influenced by the Yangtze and Yellow rivers,which contain abundant information on the regional environmental evolution.The paleo-geomorphology and its relationship with sedimentary sequence have not been clarified for the Xiyang tidal channel and adjacent areas on the central Jiangsu Coast.Based on the systematic interpretation of 380 km shallow seismic profiles obtained from the study area and the data of core analysis,the shallow seismic sequence and sedimentary environment of the Xiyang tidal channel were investigated.The main results are as follows.(1)The shallow seismic profiles obtained from the Xiyang tidal channel indicate that there is an unconformable seismic reflection interface,33?49 m underneath the seafloor.The strata underlying that seismic reflection interface are characterized by strong amplitude,medium frequency and good continuity.The strata overlying it are complex,with cutting-filling characteristic reflection in the south and east of study area,characterized by medium amplitude,high frequency and good continuity sub-parallel layers in the north of study area.(2)A comparison between the shallow seismic profiles and the data from core analysis shows that the interface identified corresponds to the top surface of the "nearshore facies" layer within the core,which belongs to the regional erosion surface.The seismic unit overlying the strong reflection interface corresponds to the "nearshore-shallow marine facies" layer at the core position,and the seismic facies unit underlying the strong reflection includes the "coastal marsh","flood plain" and "partially continental" facies layers in the borehole.(3)The spatial interpolation of the elevation of this interface and the underneath groove seismic structures reveal that several ancient channels extended to the sea in a northeast direction and converged to the low-lying area in the north of the study area.The interface represents the eroding surface of transgression during the Last Deglaciation,and its substrate represents a flood plain environment at the last stage of late Pleistocene,with ancient rivers or ancient tidal channels.Further study on the interface will help understand the evolution of the sedimentary systems since the MIS3 stage in the southwestern Yellow Sea region.