Holocene geomorphological evolution and the Neolithic occupation in South Hangzhou Bay, China

Well-known for its intensive land-sea interactions and the brilliant Neolithic Cultures, the South Hangzhou Bay (SHB) of eastern China has been the focus of early agricultural rise in adaptation to coastal environmental change. In this study, geological records from sediment cores were integrated with archaeological findings in SHB to establish the linkage between coastal geomorphological processes and Neolithic occupation since the Holocene. It showed that the Holocene geomorphological evolution of SHB was inherited from the south wing of the Late Pleistocene Qiantang incised valley. During ca.10,000–7600 cal yr BP, the paleo-incised valley was inundated and infilled by marine transgressive deposits, forming an estuary. Then coastal progradation started and gradually formed the periphery of SHB. Noticeably, freshwater wetlands firstly occurred at the apex of SHB, enabling foragers to settle down and fostering the Kuahuqiao Culture and rice exploitation (7800–7400 cal yr BP). In the semi-closed Yaojiang Valley (YJV), east of SHB, alluvial plain developed after 7800–7600 cal yr BP with coastal progradation, providing a habitat to favor the early arrivals and later became the centre of the Hemudu Culture (7000–5000 cal yr BP). Meanwhile, the Neolithic sites sporadically occurred off the YJV due to the existing inundation. The coastal progradation slowed down ca.5000–2500 cal yr BP, in association with decreased sedimentation rates. In the last 2500 years, the Shaoxing Plain and the Cixi Plain of SHB showed rapid progradation resulting from increasing sediment input and intensive reclamation. The diverse geomorphological processes of SHB were modulated by the combination of Holocene sea-level changes, sediment input and the inherited local topography. The Neolithic migrations were in phase with landscape transformations and gradual formation of coastal plain since the Mid-Holocene, facilitating the Neolithic subsistence transition from hunting-gathering to rice farming and fostering the brilliant Neolithic cultural sequence in SHB.