Paleoenvironmental Evolution And The Ancient Human Civilization In The Ningshao-hangjiahu Plain Since Last Deglacial

Ningshao Plain and Hangjiahu Plain are located desperately in the south and north bank of the Hangzhou Bay,downstream of the Yangtze River.Ningshao Plain is a transmeridional long and narrow coastal plain facing the East China Sea directly,and suffered a strong sea-land interaction,multiple transgression-regression cycles and dry-wet climate alternate changes occurred in this region,where the sea level,the coastline and the river system changed rapidly during the Holocene.As one of the three sub-culture areas belonging to the Yangtze River culture area,it developed Hemudu Culture known as the "light of the Chinese ancient civilization" in the Holocene Optimum;also it was one of the important birthplaces of rice agriculture.Ningshao Plain,therefore,is an ideal area for studying the climate change and the origin of agriculture since the last deglaciation period.The past global change research focuses on the relationship between Neolithic human activities and natural environment in the region of the Yangtze River delta-Hangjiahu Plain-Ningshao Plain,there are a few controversial issues:Whether a high sea level once existed during mid-Holocene in the East China?Whether the disappearance of the Neolithic cultures associated with extreme climatic events?Why rice farming began in here?Around the key scientific problems,this thesis attempts to restore a Holocene view of Hemudu area in the Ningshao Plain from the different space-time dimensions,including climate,environment and culture.A series of cores whose bottom layers reached to the first hard clay layer were arranged in the Hangjiahu-Ningshao area,HMD 13 Core from Hemudu Site area as the main study object of the thesis,is one of these cores,and through lithological analysis we considered that they were composed of the Holocene marine and lacustrine facies sedimentary strata;By AMS-14C dating,an accurate age framework was built;Comprehensive analysis of a variety of ancient climate proxies,including magnetic susceptibility,grain size,clay minerals,elements data by XRF Core Scanner,organic carbon and nitrogen ratio and organic carbon isotope,biomarker,etc.,combined with the micro-fossil analysis(sporopollen,diatoms)done by the project team members,a high-resolution sequence of paleoclimatic and paleoenvironmental evolution was established;Based on the work above,we can extract the response records of the global climatic events,regional sedimentary events of sea-land interaction and local extreme climatic events since Holocene.Climatic environment of different scale:the amplitude of climatic fluctuations during Holocene in the Ningshao Plain was unlikely to be enough to fundamentally change the ecological condition and vegetation,which showed that ten thousand-scale global climatic evolution has limited influence on the ancient cultures there;while the rapid cooling events and rapid transgressions of thousand-hundred scale are greatly influenced,it is more regional despite still globle.The geomorphic and hydrological environments are regional;sea-land interaction plays a leading role:a comprehensive analysis of the drillings in the study area,by the lithological data and dating data,element geochemistry(Ca,Mn),elevation and age of sites,was used to build up the regional sea level change history.From the last deglaciation period to 6.5 ka BP,the rapid sea level rise continued,appeared several times of short slowly rising or stagnation;about 6.5 ka BP appeared a long time stagnation;since then till 5 ka BP,slowly rose;around 5 ka BP the sea level was regressive,after that it rose to today's altitude.In the Holocene Optimum it did not correspond with the high sea level in the study area.For human's settlements and the origin and development of agriculture,the local environment is particularly important,including the ecological environment and extreme environment:on the basis of accurate dating data,through micropaleontological,sedimentological and geochemistrial evidences it indicated the storm surge(8.0 ka BP,4.2 ka BP)and flood(6.5 ka BP,6.2 ka BP)and other extreme weather events of the hundred-ten years-scale.Based on the numerous previous research achievements of Neolithic sites scattered in the middle and lower reaches of the Yangtze River region,a sequence of Hemudu Culture was clarified.Systematically in this paper,the hydrological,geomorphological,and ecological environment evolution and ancient culture response were explained;in particular the spatial and temporal pattern of the settlement transition and agricultural development under the extreme environment condition was concerned.In 7 ka BP the sea water which has invaded to north of Zhejiang-Fujian hills began to fade,and so Hemudu area was first exposed to become land on the Ningshao Plain,Yaojiang river valley has become the first inhabited region;in 7-5.9 ka BP the Hangzhou Bay was cut off by a deep river bay completely,in 5.8?5.2 ka BP because of the stagnation of the sea level,the deposition rate increased,the gulf became narrow,and then the one-way cultural penetration from north to south occurred;in 5 ka BP,the Qiantang River Estuary separated from the Yangtze Estuary basically,and the main body of the Hangzhou Bay formed,which induced that the Yaojiang River diverted to east,and the Hemudu site exposed to face the sea water intrusion,humans had to escape backwards to the south hills.Ancient cultures tend to develop from independent micro habitats to more syncretic and wider habitats.Agriculture is an excellent fruit from the coupling of natural environment and human civilization.Although independent agricultural development is closely related to the growth of the human civilization degree,a wide range agricultural activities must inevitably suffer the influence of a large scale natural factor that the climate factor,as to how much influence the proportion of,still need further environmental archaeology research.