The Mid-late Holocene Hydrological Environment Changes Recorded In The Section Of Tianluoshan Site In Zhejiang

The rising sea level caused by global warming and the changes in the extreme climate environment have brought enormous challenges to human production and life,and have been closely watched by the scientific community and the international community.In the context of the global climate environment,how humans adapt to changes in the environment is one of the problems that the scientific community needs to solve urgently.As the latest geological stage in the geological history period and modern times,the Holocene has nurtured many Neolithic cultures.It is an important period for the development of agricultural origin and the prosperity and development of human culture.It has also become an ideal period for studying the relationship between climate change and human development.Located in the Yangtze River Delta-Hangjiahu-Ningshao Plain in eastern China,it has nurtured many Neolithic cultures and is one of the origins of rice farming in China.Located in the Ningshao Plain on the south bank of Hangzhou Bay,it is very representative of agricultural origin and climate change,while the Yuyao Basin in the eastern part of the Ningshao Plain is a small east-west mountain depression,due to the northern Cinan Mountains and The barrier function of the Zhoushan Islands in the east is in a relatively closed sedimentary environment,which can be protected from the tides and wind waves.The sedimentation is stable,the sediment preservation conditions are good,and the stratum is complete and continuous,which is conducive to the research.At the same time,the place is bred as the Hemudu culture known as "the light of the ancient civilization of China".The Tianluoshan ruins are one of the typical representatives of Hemudu culture and have rich cultural relics.The Yuyao Basin area has become an ideal area for studying the relationship between environmental changes and prehistoric human activities since the Holocene.The predecessors systematically studied the environmental background and cultural origin of cultural sites in the Ningshao Plain,and also obtained a large number of research results,represented by Zheng Yunfei,Li Minglin and Wang Shuyun.Regarding the environmental background of the ruins culture,different scholars have different opinions and there is much controversy.The reason for the controversy may be that different scholars choose different sections in the same site for research,which is affected by the difference in micro-geomorphic evolution process in the Tianluoshan site.In view of the inadequacies in the research of the Ningshao Plain.This study selected two sections in the Tianluoshan Site,which are the partitions of the south wall between the T005 west wall(T005W)and the probes T207 and 307(T207-307S)obtained continuous stratigraphic profiles with thicknesses of 263 cm and 150 cm,respectively.Systematic lithologic stratigraphic description,accelerated mass spectrometry(AMS)14C dating,and high-resolution XRF(X-ray fluorescence spectroscopy)elemental scanning,a comprehensive analysis of diatoms and particle size.Combined with the research results of the natural borehole TLS1402 in the paddy field near the site,the comparative analysis was carried out.The results show that:1)7.0?6.3 cal ka BP,the coastline retreats eastward,and the whole cultural layer is characterized by the freshwater marsh wetland sedimentary environment,which only shows the deepening or shallowening of the water body to different degrees.It is presumed to be affected by climate precipitation,and the climate is humid at different stages.There is a certain difference between the degree of drought and prehistoric humans.There is no obvious sedimentary discontinuity between the cultural layers on the T207-307S section,mainly because the terrain is relatively high and is not directly affected by flooding.There is a lack of cultural layer on T005W,which may be the lower terrain of the probe,which is highly vulnerable to the direct erosion of the flood,resulting in discontinuity and loss of sediment;2)about 6.3?6.0 cal ka BP,the cultural layer recorded by section T005W The overlying stratum(2nd layer)is unconformity with the cultural layer and is a rapid deposition of about 4.2?4.0 cal ka BP.At this time,the area may be affected by floods caused by multiple storm surges,bringing a lot of seawater.Thereby a sedimentary environment characterized by salt water and brackish water is formed.However,it is worth noting that the second layer of the overlying strata is in unconformity with the cultural layer,and there is a large gap in the age,and there are sedimentary discontinuities,which are not enough to explain the reasons for cultural decline.