Stratigraphy and paleoenvironmental changes in the Yangtze Delta during the Late Quaternary |
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| Institution: | 1. Shanghai Institute of Geological Survey, Shanghai 200072, China;2. State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China;1. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China;2. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;1. School of Geography and Ocean Science, Ministry of Education Key Laboratory for Coast and Island Development, Nanjing University, Nanjing, China;2. State Key Laboratory of Estuarine and Coastal Research, School of Marine Sciences East China Normal University, Shanghai 200062, China;3. CSDMS Integration Facility, INSTAAR, University of Colorado, Boulder, CO 80309-0545, USA;4. Qingdao Institute of Marine Geology, Qingdao 266071, China;5. Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China;1. College of Marine Geoscience, Ocean University of China, Qingdao, China;2. National Deep Sea Center, State Oceanic Administration, Qingdao, China;3. The First Institute of Oceanography, State Oceanic Administration, Qingdao, China;4. Department of Marine Science and Technology, Federal University of Technology, Akure, Nigeria |
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| Abstract: | The Yangtze Delta area may be subdivided into paleo-valley and paleointerfluves of the last glaciation. The postglacial transgressive sedimentary cycle (PTSC) on the front zones of the paleointerfluves is composed of marsh-nearshore and barrier-lagoon, shallow marine and nearshore-tidal flat units, with a basement in stiff clay. The PTSC in back zones of the paleointerfluves consists of lacustrine-marsh deposits. The PTSC in the incised valley contains river channel, floodplain-estuary, estuarine-shallow marine and deltaic units, with an erosional surface at its bottom. The stiff clay and the erosional surface constitute the PTSC lower boundary.The stiff clay, consisting of a paleosol, experienced deposition alternating with pedogenesis during the falling of sea-level during δ18O stage 3; ongoing pedogenesis in the sea-level lowstand of δ18O stage 2; and early diagenesis after paleointerfluve inundation by the sea-level rise of δ18O stage 1. The climate during the paleosol formation was temperate with more than 500-mm a?1 rainfall and frequently fluctuating groundwater.The Yangtze River incised its course during falling sea level of stage 3, and a huge incised valley was formed during the sea-level lowstand (stage 2). The filling of the incised valley took place during the postglacial sea-level rise, and delta formation occurred at a late stage of PTSC development. |
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