The Landscape Evolution And Its Influence On Liangzhu Culture In The Liangzhu Since The Last Glacial Maximum

The large river delta areas are vital food-producing areas and population centers.However,as low-lying littoral regions,they are highly vulnerable to even minor sealevel changes,mainly because most deltas actively subside and their sediment supply has been curtailed.Moreover,warming climate and accelerating sea-level rise have become a consensus,which would intensify coastal erosion,saltwater penetrations,floods,and storm tides.It is essential to understand the relationship between the past landscape evolution and ancient human adaptation during the Holocene to predict landscape evolution in these areas to future climate change and sea-level rise.During the early Holocene,the Yangtze delta,Hangzhou-Jiaxing-Huzhou(Hangjiahu)delta,and Ningbo-Shaoxing(Ningshao)delta occurred transgression due to the rapid rise of sea level.During the middle Holocene,marine regression occurred in those areas as the sediment supply rate exceeded the sea-level rise rate during the period of deceleration in the rate of sea-level change.Subsequently,the Majiabang culture,Songze culture,Liangzhu culture,Qianshanyang culture,Guangfulin culture,and Maqiao cultures appeared one after another in the above areas.The archaeological ruins of Liangzhu City(approximately 5300?4300 cal yr BP),located on the southwestern edge of the Yangtze Delta,were listed on the UNESCO World Heritage register in 2019.Therefore,the Yangtze delta,especially the core area of the Liangzhu culture——Liangzhu cite area,is an ideal area for studying the relationship between landscape evolution and ancient human adaptation in the Neolithic period.Based on the above information,this research carried out drilling and sampling in the core area of Liangzhu culture——Liangzhu Ancient City,and obtained core LZ1601.Besides,drilling(core LZ1501)was also carried out in the natural depositional area outside Liangzhu Ancient City.Both cores have penetrated the Holocene strata to reach the paleosol layer(hard clay layer)belonging to the Pleistocene strata.1.The detailed landscape evolution since the last glacial maximum at the Liangzhu area.From the last glacial maximum to the early Holocene(before ca.9400 cal yr BP),the Yangtze delta(including Liangzhu area),Ningshao delta,and the extensive continental shelf of the Yellow Sea and the East China Sea areas are exposed surface.A paleosol,known as the First Hard Clay layer with a thickness of several meters,was widely developed in the Yangtze delta(including Liangzhu area),Ningshao delta,and the extensive continental shelf of the Yellow Sea and the East China Sea areas.Loose sediments of sand and gravel covered the slope of the low mountains.In the early to middle Holocene(ca.9400?7600 cal yr BP),the Liangzhu area was rapidly submerged by a marine transgression from east to west at ca.9400?7900 cal yr BP.Marine regression occurred eastward from the Liangzhu area at approximately7900?7600 cal yr BP as the sediment supply rate exceeded the relative sea level rise rate during the period of deceleration in the rate of relative sea level change.The mid-late Holocene(after ca.7600 cal yr BP),seawater sediment,the thickness of several meters with strong hydrodynamic characteristics,was developed at the Liangzhu area soon after the initiation of land formation(7600?6600 cal yr BP).Similar deposits formed at almost the same time(approximately 7400 cal yr BP)have been observed at Kuahuqiao,located to the southeast of Liangzhu and separated by the Qiantang River.After a detailed geological and sedimentological analysis,as well as comparing the corrected stratigraphic elevation range of seawater sediment at this stage with the relative sea-level elevation range of the Yangtze delta at that time,the results showed that the formation of the deposits might be caused by an overbank flooding event deposit,rather than direct marine inundation.The Liangzhu City area was dominated by freshwater and was vulnerable to mountain floods and saltwater intrusion until ca.5100 cal yr BP.After that,the Liangzhu area gradually dried out as the coastal plain developed farther eastward,and the establishment of the 5100-year-old hydraulic enterprise system(provided multiple functions,such as flood control,transportation,and irrigation),combined with the superior geographical location of the Liangzhu area surrounded by hills.Therefore,the geomorphic environment of the Liangzhu area is very suitable for human activities and settlements,and the Liangzhu area has quickly become the core area of Liangzhu culture.2.Reconstruction of the vegetation and climate information.From last glacial maximum to around 9400 cal yr BP,the vegetation coverage is low,and the climate is cold and dry.From 9400 to 6600 cal yr BP,the Liangzhu area was warm and wet,the vegetation coverage is high,and the forest vegetation is mainly with oak forest and Pinus forest.6600?4200 cal yr BP,the temperature declined,and the forest vegetation was significantly reduced due to human activities' influence.3.The geomorphic evolution controlled the spatial and temporal distribution of Neolithic sites in Hangjiahu-Ningshao plain(including the Liangzhu area).Research on the spatial-temporal relationship between the geomorphic environment and Neolithic sites in Hangjiahu-Ningshao plain(including Liangzhu area)shows a stable geomorphic environment is a key factor for the development and evolution of Neolithic sites during the Holocene.On the one hand,the regression during the middle Holocene provided a material basis for Neolithic sites' development.On the other hand,the stable land environment directly determines the number and scale of Neolithic sites' development.For example,in the Liangzhu area,although the regression occurred at around 7600 cal yr BP,a stable terrestrial environment did not appear until approximately 5100 cal yr BP.Therefore,the Neolithic sites in this area belong to the middle and late Liangzhu culture.