Study Of Prehistoric Human Activities And Its Environment Background Around Lake Donggi Cona During Mid-Holocene

Northeastern Tibetan Plateau?NETP?is an important corridor for prehistoric human to settlement of the inner Tibetan Plateau?TP?.It has the most densely distributed sites from Late Paleolithic to Neolithic.Understanding the relationship between prehistoric human activities and environmental evolution in this region is significant for reveal the adaptation mechanism of human beings to extreme environment of the TP.However,most of previous researches have been carried out on the lower altitude area?<4000 m a.s.l?of this region,while the archaeological investigations in the higher altitude area is relatively weak.DJCN 3-2-2 is a microlithic site located on the northern shore terraces of Lake Donggi Cona,NETP.A quantity of recently excavated stone artifacts and hearths?DJCN 3-2-2?on the northern shore terraces of the lake provide ideal materials for the study of the relationship between prehistoric human activities and environmental changes in the hinterland of TP.In this study,we carried out systematic typological analysis of stone artifacts discovered in site DJCN 3-2-2 and accelerator mass spectrometry?AMS?¹⁴C dating for charcoals from the hearths.Meanwhile,optically stimulated luminescence?OSL?dating were carried out for the DJCN 3-2-2stratigraphic profile,and environmental proxies including grain size,charcoal,magnetic susceptibility,fungal spore,and pollen from the stratigraphic profile were also analyzed.We try to reveal the time,characteristics and subsistence strategy of prehistoric human activities,as well as the environmental background of prehistoric huma's activities.Combining the archeological data in NETP,we have discussed the prehistoric cultural systems in different altitude and its evolution process during middle Holocene in the NETP.The primary conclusions are as follows:?1?A large number of stone artifacts and 10 hearths were found in DJCN 3-2-2,the AMS¹⁴C dating results of charcoal in hearths and burnt soils are between 5.4 and5.0 ka BP,which are consistent with result of OSL dating from charcoal layer in DJCN3-2-2 profile?5.5 ka BP?.A total of 256 pieces of stone artifacts were collected on the surface in the site,including 56 flakes,7 microblade cores,55 microblades,12blades,10 tool and 116 chunk and fragments.According to the systematic typological analysis of stone artifacts,we suggest that the site was a seasonal,long-term center camp used for stone artifacts processing,food processing and consumption,as well as daily necessities production.?2?Charcoal,magnetic susceptibility and fungal spores results reveal that human activities began at 5.8 ka BP and significantly intensified during 5.6-5.5 ka BP in the lake area,and then the activity intensity gradually weakened.Pollen analysis reveals that the vegetation was dominated by alpine grassland during 5-8-5.5 ka,which indicated a warm and humid climate condition.Previous researches show that the Lake Donggi Cona might have changed from saltwater to stable freshwater ones at 5.8ka BP due to earthquakes,which coincided well with the time of prehistoric human activities revealed in this study.Therefore,prehistoric human activities in the lake area were closely related to environmental changes.?3?The prehistoric culture recorded in DJCN 3-2-2 section should represent the last group of pure microlithic hunting-gathering humans in the NETP.Afterwards,under the impact of Neolithic culture in lower altitude of upper Yellow river valley,the microlithic hunting-gathering culture in Lake Donggi Cona area gradually transited to Neolithic culture.A typical example is the Zongri culture,which has distinct indigenous characteristics and strongly influenced by Majiayao culture,was formed in the Gonghe Basin that between the transitional zone of the Donggi Cona and upper Yellow river valley.This study provides new insight for understanding the behavioral patterns of prehistoric humans adapting to extreme environments,and for exploring the activities and evolutionary history of prehistoric humans in higher altitude area in the TP.