Sedimentary Environment Evolution Of Liaodong Bay During The Late Quaternary

The Liaodong Bay located in northern of the Bohai Sea is a typical semi-closed epicontinental sea. It had submerged by the sea for many times since the late Quaternary, which formed interactive marine & terrestrial stratigraphy. There are plenty of informations of sea level change, depositional environment evolution, sediments and climate change etc in sedimentary stratigraphy, as the research object of which, it can rebuild depositional environment and process and reveal the evolution trend of depositional environment.Based on the core LDD-7 and 3255 km high-resolution shallow seismic profiles recently acquired in Liaodong Bay, the article makes a detail division of sedimentary structure and studies sedimentary characteristics and environment evolution since the late Quaternary.Three seismic units are defined from shallow seismic profiles:units SU1, SU2 and SU3, in which unit SU2 is divided into two sub layers SU2-1 and SU2-2. Using the contrast between seismic profiles and core LD01(water depths 14m) and core C05 (water depths 30m), unit SU1, SU2 and SU3 are respectively Holocene marine sedimentary strata, Pleistocene continental strata and Pleistocene marine sedimentary strata, of which are happened during MIS1,MIS2 and MIS3.Core LDD7 is located in the central Liaodong Bay, of which water depth of sampling is 30.5m and drilling footage is 50.1m. On the analyses of lithology, sedimentary tectonic, AMS 14C age and micro-paleontology combination characteristic, with contrast to the shallow seismic profile, the core LDD7 is divided into 4 depositional units, which are named U1, U2, U3 and U4 from up to down, of which environmental changes are to be interpreted happened during MIS1, MIS2, MIS3 and MIS4. U3 is divided into 4 sub unit which are U3-1, U3-2, U3-3 and U3-4.The sedimentary environment of Liaodong Bay since late Pleistocene was rebuilded through the analysis of shallow seismic profiles and drilling core. Since the’ last glacial period(MIS4), the climate in study area changed alternately, while the sea level changed along with the climate variation, then Xianxian transgression and Huanghua transgression happened. U3 and U1 marine sedimentary stratas are deposited.The sedimentary environment evolution experienced fluvio-lacustrine-interactive marine & terrestrial deposit-lacustrine facies/flood plain-shallow sea during late Pleistocene.