ENVIRONMENTAL EVOLUTION AND TIDAL SAND SHEET SEDIMENTATION IN LATE QUATERNARY IN THE EAST BOHAI SEA

According to analysis of lithology, biology and chronology, hole CD5 can be identified to have two marine beds and two continental beds from top to bottom. The two transgressive periods were from 39 to 22 kaBP and from 9 kaBP to the preseal day. Tidal delta of the Bohai Sea around hole CD5 has had rapid sedimentation since 3600-2400 kaBP and formed tidal sand sheet 4.8 m in thickness. Through analyzing more than 10 holes in the east Bohai Sea, the environmental evolution of ridal sand sheet from Holocene was clear and the sand sheet experienced three evolution stages(9-8 kaBP,8-3.6 kaBP,3.6-2.4 kaBP), and now it is relatively stable.