The Holocene Regression And Land-formation Process And Its Influence On Human Activities In Dongyuan Site And Kaizhuang Site Of The North Jiangsu Province

The Holocene sea-land changes directly shaped the modern coastal landform and the environment for modern human survival and development.The development of human civilization and the scope of human activities in the Neolithic age have also been restricted by the changes of coastline.Therefore,looking for the information of sea-level change and human activities and exploring the impact of Holocene sea-land changes on human activities in the Neolithic Age in the archaeological sites including the Holocene marine facies and Neolithic culture is of great theoretical significance to reveal the interaction mechanism between Holocene sea-level change and Neolithic human activities.It can also provide effective scientific basis and theoretical guidance for the sustainable economic and social development of coastal areas and the formulation of strategies and plans to adapt to modern and future sea-level changes.In this study,based on the detailed analyses of AMS ¹⁴C dating,marine microfossils,grain size,environmental magneitsm and redox sensitive elements,we found the Holocene marine sedimentary in the layer of Dongyuan Site and Kaizhuang Site and reconstructed the evolution history of its sedimentary environment.On this basis,combined with previous research results,the evolution history of regional stratigraphy and sedimentary environment is compared,and the evolution history of early and middle Holocene paleogeographic environment in Lixiahe area is restored.Based on the time-space distribution and cultural connotation of archaeological sites in the eastern Jianghuai Region,this paper discusses the influence of land and sea changes on the development of human civilization in the Neolithic age.The results show:(1)The AMS ¹⁴C datings in the 2nd and 3rd lithologic section of Core DY-2013 in the Dongyuan Site show that the deposition occurred in the early and middle Holocene.In the 3rd lithologic section,the lithology implies a reducing environment.The large change of sedimentation rate indicates that the sedimentary environment in this stage has changed greatly.The grain size characteristics show that the sediment dynamics suddenly became larger in the latter stage.The magnetic properties show that Fe-sulphides are the main magnetic mineral due to the reductive diagenesis.The changes in concentration,coercivity and grain size with the depth of the magnetic particles represent the terrigenous residual magnetic particles after different degrees of dissolution.Coarser grained paramagnetic minerals dominate the magnetic properties,and the emergence of high-coercivity magnetic minerals in the upper part express the change in the depositional pattern.The V/(V+Ni)ratios reveal a stable anaerobic environment,and the water stratification is not strong.The results of multi-proxy from the 3rd lithologic unit in Core DY-2013 indicate a coastal shallow water environment and tempestite deposits in its later stage.The neighbourhood of Core DY-2013 has changed from shallow water to tidal flat in 5700-9200cal.a BP,the process of regression and land formation indicates the formation of Xigang underwater sandbar.And the Funing area experienced a sedimentary environment evolution from shallow sea to tidal flats(coastal dunes)in the early to middle Holocene.(2)The AMS ¹⁴C datings in the 2nd and 3rd lithologic section of Core KZ-2013 in the Kaizhuang Site show that the deposition occurred in the early and middle Holocene.In the 4th lithologic section,the lithology implies a reducing environment.The large change of sedimentation rate indicates that the sedimentary environment in this stage has changed greatly.The marine micropaleontology indicates the evolution of the sedimentary environment from an intertidal zone to a supratidal zone.The grain size characteristics show an evolution of the dynamic condition in depositional environment first decreases and then increases and from single to complex from.The magnetic properties show that Fe-sulphides are the main magnetic minerals due to the reductive diagenesis.The magnetic characteristics with depth represent a change of sedimentary environment,the magnetic particles derived from the original terrigenous clastic weathered clay and a shallowing trend of water depth.The V/(V+Ni)ratios reveal a stable anaerobic environment and weak water stratification,with higher oxygen content and a shallowing trend of water depth.The results of multi-proxy from the 4th lithologic unit in Core KZ-2013 indicate a sedimentary environment evolution from intertidal zone to supratidal zone in 10300?5200 cal.a BP.According to the comparison of regional sedimentary evolution history,Core KZ-2013 is part of the north shore sand embankment of the Yangtze River formed in the early and middle Holocene,the process of regression and land formation indicates the formation of the north shore sand embankment of the Yangtze River.Kaizhuang site is located on the north shore sand embankment of the Yangtze River formed in the middle Holocene.(3)The process of regression and land formation of Dongyuan Site and Kaizhuang Site indicate the formation and connection in the middle Holocene of Xigang underwater sandbar,the south shore sand embankment of the Huaihe River and the north shore sand embankment of the Yangtze River,which around Lixiahe Area.This provides more space and convenient conditions for the survival and production activities of the ancestors,and promotes the development of human civilization in the Neolithic age.At the same time,combined with the changes of paleogeographic environment and the time-space distribution and cultural connotation of archaeological sites in Lixiahe area,it can be seen that under the conditions of sea invasion and lagoon and other natural factors,there is still cultural communication between the South and north sides of Lixiahe depression.This shows that Xigang sandbar,the only land channel connecting the north and the south of the Lixiahe Region during the middle Holocene,has become the only channel to promote the spread and exchange of Haidai civilization in the north and Taihu civilization in the southin the eastern Jianghuai Region during the late Neolithic age.