| Since the last deglaciation,the climate has been warming,causing rapid melting of polar ice caps and mountain glaciers and leading to a significant rise in global sea levels and a notable change in the geomorphic patterns of estuarine and coastal areas.However,during the mid-Holocene,the rate of sea-level rise slowed down,and against the backdrop of increased monsoon precipitation,large amounts of terrestrial material were transported to the estuarine regions,forming the embryonic stage of modern deltaic and coastal plains.These newly formed lands possess abundant natural resources,attracting ancient humans to settle and develop a series of distinct Neolithic cultural sequences that have contributed significantly to the history of human development.Using the example of the southern wing of Hangzhou Bay in eastern China,the Holocene climate-sea level changes and strong land-sea interactions not only shaped the regional geomorphic environment but also promoted the formation of a Neolithic cultural sequence represented by the Shangshan-Kuahuqiao-Hemudu-Liangzhu cultures,providing an ideal case for studying the human-environment relationship in coastal zones.Previous studies have revealed the stratigraphic evolution framework and geomorphic development processes of the Holocene climate-sea level changes in the southern flank of Hangzhou Bay,providing important fundamental data and analysis for understanding the early human-environment relationship in this region.It is worth noting that some studies have indicated the widespread adoption of rice agriculture during the later period of Hemudu Culture,representing more advanced productivity and socioeconomic levels at that time.However,the subsequent decline of the Liangzhu Culture sites,in contrast to the unprecedented prosperity of the Liangzhu Culture in the Taihu Basin,remains unclear.To answer this question,this paper selected the Ningfeng Plain,where the land-sea interaction is the strongest during the Holocene,as the study area,and obtained three sediment cores（LJQ,DJT,YS）near the Lujiaqiao site in the southwest,Dongjiatiao site in the southeast,and Yushan site in the north,respectively,to conduct sedimentology,chronology,environmental magnetism,and microfossil analysis.Based on the AMS14C chronology framework established for the three locations and the analysis results of various environmental indicators from the drilling cores,the Holocene land-sea changes in the Ningfeng Plain were reconstructed and compared with the drilling and site profiles from other regions in the southern flank of Hangzhou Bay to further elucidate the geomorphic evolution processes.Combining with the archaeological data of Neolithic sites in the two wings of Hangzhou Bay,the response relationship between the Holocene paleoenvironmental changes in the Ningfeng Plain and the human activities of the Neolithic era was analyzed and discussed.We have drawn some conclusions as follow:（1）The Holocene environmental changes in the Ningfeng plain can be roughly divided into four stages（I-IV）.I:Early Holocene-9.6 cal kyr BP.The stiff mud at the bottom of core LJQ and DJT in the southern part of the plain indicate that the Ningfeng plain was not impacted by postglacial transgression until 9.6 cal kyr BP.The geomorphic environment was dominated by glacial incised valley and interfluve.II:9.6-7.2 cal kyr BP.The lithological characteristics and foraminifera of the core LJQ and DJT indicate that during the Early to Middle Holocene,with the rapid rise of sea-level,sea water entered the Ningfeng Plain from east to west,and gradually invaded the hinterland of the Ningfeng plain westward during 9.6-8.1 cal kyr BP,then submerged the Yindongnan Plain and Yinxi Plain.According to the variation trend of foraminifera in the core LJQ,the transgression enhanced during 8.1-7.6 cal kyr BP and a coastal-littoral environment emerged,then it gradually transitioned to an estuary during 7.6-7.2cal kyr BP with the slowing down of the sea-level rise.III:7.2-5.5 cal kyr BP.During this period,the lithology of core LJQ and DJT changed significantly,with foraminifera and shell fragments disappearing from the boreholes,and the content of plant fragments and peat increasing,indicating that the hinterland of the Ningfeng Plain was no longer submerged by seawater after about 7.2 cal kyr BP.The indicators from the core LJQ and former studies demonstrated that a tidal brackish marsh formed during the regression around 7.2-5.5 cal kyr BP,the hydrological environment was turbulent under the influence of the sea-level change.IV:Since 5.5 cal kyr BP.The environmental indicators of the core LJQ and YS show that after 5.5 cal kyr BP,with the stability of sea level,the seawater gradually receded from the hinterland of the Ningfeng plain,and after around 3.7 cal kyr BP,it completely withdrew from the Ningfeng Plain.The regional hydrological environment was steady and the coastal plain gradually formed.（2）According to the archeological excavation records,the Neolithic sites first appeared in the hinterland of the Ningfeng plain during 6.5-6.0 cal kyr BP.Based on the environmental evolution process,we could infer that the instability of hydrological condition hindered the development of the Neolithic culture in the Ningfeng plain until5.5 cal kyr.A steady freshwater environment formed in the Ningfeng plain after 5.5 cal kyr BP,providing appropriate conditions for Neolithic human to settlement and farming,the number of the Neolithic sites increased significantly during this period.The stone plow,charred rice husk unearthed from the relics of the sites and an increase in Poaceae（≥38μm）also suggested an increased human activity.However,compared with the Liangzhu culture in the Taihu plain,north Hangzhou Bay,the Neolithic culture in south Hangzhou Bay was not proser after 5.5 cal kyr BP,but gradually diminished.Thus,we could infer that the main causes for this discrepancy may not lie in the environment,but in the society and culture.For example,the transfer of cultural centers led to human exodus,or the invasion of exotic culture. |
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