Paleoenvironmental Evolution in the Inner Shelf of the East China Sea Since the Last Deglaciation
XU Fang-jian1,2 LI An-chun1 XIAO Shang-bin3WAN Shi-ming1 LIU Jian-guo4 ZHANG Yong-chao5(1. Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao Shandong 266071;2. Graduate University of Chinese Academy of Sciences, Beijing 100049; 3. College of Civil & Hydroelectric Engineering, China Three Gorges University, Yichang Hubei 443002; 4. Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301;5. Research Institute for Exploration & Development, Petrochina Jidong Oilfield, Tangshan Hebei 063004)
Based upon analysis of lithology, grain-size and AMS14C dating for Core EC2005, located in the mud area off the Zhejiang-Fujian coast in the inner shelf of the East China Sea, the paleoenvironmental evolution can be ascertained. The hydrodynamic conditions and sedimentary environment changed greatly which could have been an integrated result of the varieties of lacustrine water depth, sea-level and climatic changes. From the bottom 60.20 m to 41.00 m (17.3～13.1 ka BP), a lacustrine delta developed, which can be divided into three facies: prodelta, delta front and delta plain. The delta sediments are deduced to mainly from the local drainage area. The sea water arrived at the study area at 13.1 ka BP and a 41 m thick sediment formed from then on, which can be divided into three facies: foreshore, nearshore and shallow sea. The facies evolution was well corresponding to the sea level changes, the hydrodynamic conditions changed greatly also during this period. From 12.3 ka BP, the study area was influenced by Zhejiang-Fujian Coastal Current (ZFCC), and Yangtze-derived materials had been transported southward from that time. Since 7.3 ka BP, the sedimentary environment is dominated by the ZFCC, and the homogeneous mud sedimentation began to form. The worldwide climatic events such as the Younger Dryas episode and the 8.2 ka event were well recorded in the core.