Grain size distribution of sediment of core YRD-1101 in the western margin of the modern Bohai Sea since the latest Pleistocene and its environmental change

Three stages of sedimentary environment evolution since MIS 5 were recognized based on the data of grain size analysis, AMS¹⁴C dating, OSL dating, sedimentary characteristics, benthic foraminifera and ostracoda identification in the upper part of core YRD-1101 drilled in the modern Yellow River Delta, and comparison with surrounding boreholes. Three stages of sedimentary evolution are identified. (1)Interactive deposition of rivers and marine facies were formed during the Late Pleistocene-Early Holocene. Among them, the transgressive sediments in the MIS5c phase were formed in a medium hydrodynamic conditions, the transgressive sediments in the MIS3 phase were formed in a weak hydrodynamic environment, and the river sediments in the MIS2 phase were formed in a strong hydrodynamic environment. (2) The nearshore and shallow sea deposits during the Holocene formed in a strong and stable environment. (3) Modern Yellow River Delta sediments deposited since 1855 A.D. were formed in weak to medium sedimentary dynamic environments. Sea-level changes and neotectonic subsidence have been the major factors controlling the sedimentary evolution on the western margin of the modern Bohai Sea since MIS 5. In addition, the sediments were transported to the study area from Yellow River, which had a significant influence on transgression intensity.