Early–Middle Holocene marine–terrestrial changes in the southeastern Lixiahe Plain, East China: Land-forming mechanisms, regional significance, and implications for Neolithic cultural origins

The southeastern Lixiahe Plain (SELP) is the site of the only identified Neolithic human settlements in the eastern Northern Jiangsu Plain, East China, and it also represents the junction of the Lixiahe Plain (LP), the Northern Jiangsu coastal Plain, and the Yangtze River Delta northern flank Plain. Based on previous studies and lithology, marine micropaleontological analysis, and the results of AMS 14C dating of three sets of strata from the Neolithic “ruins area”, we discussed the timings and mechanisms and the regional significance of the Early–Middle Holocene marine–terrestrial transitions in the SELP as well as the origins of its Neolithic culture. A rare phenomenon is identified in the study: Under the background of the rapid sea-level rise in the Early Holocene, the eastern part of the area accreted from the marine environment to a coastal tidal flat at approximately 8000 a BP (8900 cal a BP). This accretion was due to the obstruction of the palaeogeomorphic uplift belts to the east and south of the LP and the convergence and accumulation of sediments caused by the radiating tidal current field in the South Yellow Sea. The western part transformed into a swamp environment at approximately 5500 a BP (6300 cal a BP) due to the formation of the Yangtze River north coastal sand bank during the Early to Middle Holocene. As the first new land formed in the study area during the Holocene, the marine–terrestrial changes of the SELP formed the boundaries of the spatial evolution of the three plains, thus limiting their respective evolution range. As the archaeological evidence necessary to build a complete evidence chain is lacking, palaeogeography and traffic problems limit our current understanding on the Neolithic cultural origins in the SELP, which may be the future direction of research efforts.