Sedimentary Characteristics and Environmental Evolution of the Late Quaternary Incised-Valley Fills in the Nantong Area of Jiangsu Province, China

Key words: 
• Late Quaternary stratum /
• sedimentary characteristics /
• sequence boundary /
• incised valley /
• Nantong area of Jiangsu province

Abstract: This paper studies the sedimentary characteristics, stratigraphic sequence, sequence boundary and environmental evolution of the Late Quaternary incised-valley fills in the Nantong area, Jiangsu Province, based on the detailed analyses of core lithology, paleontology, ¹⁴C dating, and so on. The results show that there are three episodes of incised valley developed in the study area resulting in the formation of distinct sedimentary sequences, which correlate to the early stage, the middle stage, and late stage of late Quaternary, respectively, and showing three episodic sea-level change "low sea level-transgression-high sea level-regression". The early two systems are incomplete due to the late strong incision and erosion, and are characterized by the superposition of fluvial sediments; while the last postglacial sequence is relatively complete with five sedimentary facies generated, i.e., the fluvial channel, floodplain, estuary, shallow marine, and delta. The basal erosional surface of the lastglacial incised valley fill, which was formed during the Last Glacial Maximum due to fluvial incision, can be correlated with the surface of stiff clay on the interfluves, indicating a significant chronostratigraphic nature.