Early mid-Holocene sea-level change and coastal environmental response on the southern Yangtze delta plain, China: Implications for the rise of Neolithic culture

We used a series of Holocene sediment cores with AMS ¹⁴C dated basal saltmarsh peat and supratidal sediment to reconstruct early mid-Holocene sea-level change on the southern Yangtze delta plain. We also synthesized results for ca 150 late Quaternary cores, as well as archeological data to reveal the unique interplay between coastal evolution and Neolithic cultural response. Relative sea level was ca -16.5 to -14.5 m from 8600 to 8500 cal BP and ca -6 to -4 m from 7400 to 7200 cal BP, reflecting the rate of eustatic sea-level rise but being ca 10 m higher possibly because of the effect of hydro-istostasy. Three late Pleistocene interfluve terraces, T3 to T1, were revealed at burial depths of <5 m, 5-15 m, and 20-30 m, respectively, lying between the paleo-incised mega-valleys of the Yangtze River in the north and the Qiantang River in the south, during the last glacial maximum. During the early mid-Holocene, the combined effect of rapid sea-level rise and the huge sediment accommodation space of the mouths of the two mega-rivers resulted in widespread inundation by brackish water and the shoreline retreated onto the highest terrace (T3). Although seaward migration of the Yangtze delta probably began at ca 7300 cal BP, saltmarsh and tidal flats dominated on the southern Yangtze delta plain until ca 6500 to 6000 cal BP when sea level became relatively stable and the shoreline prograded rapidly from T3 to the seaward boundary of T2. The concurrent formation of the freshwater-dominated Taihu Plain allowed Neolithic settlement and development of agriculture.