Study Of Microlithic Human Activities And Environmental Background In Qinghai Lake And Eling Lake Areas Of Qinghai-Tibetan Plateau

The prehistoric human activities on the Qinghai-Tibetan Plateau attracted numerous scholars'attention,due to its hypoxia and cold environmental conditions.At present,research on the Microlithic human activities and environmental evolution on the Qinghai-Tibetan Plateau is mainly concentrated on the lower-altitude areas?<4000 m?in the northeastern plateau.The process of prehistoric human's adaptation to extreme environments at higher altitudes and the interrelationships of these prehistoric humans with the hunter-gatherers in the lower altitude regions during early to middle Holocene are remains unclear,which impede the comprehensive understanding of prehistoric human activities on the Qinghai-Tibetan Plateau.In this study,we have carried out archeological investigation to the Copper Wire site?TX-3-1?and the Eling Lake site?ELH-3?.Optically stimulated luminescence?OSL?and AMS¹⁴C dating samples were collected for age determination from the TX-3-1and ELH-3 stratigraphic profile,respectively.Combining the reconstructed Environmental Index?EI?of Qinghai Lake,and environmental proxies including charcoal,pollen,fungal spores,grain size and magnetic susceptibility analysis from the ELH-3 stratigraphic profile,we have obtained some conclusions as follow.?1?There are 9 hearths were found in TX-3-1 site,the AMS¹⁴C dating results of charcoal in hearths and burnt soils are range between 12144¹1089 cal.a BP Characteristics of the hearths and stone artifacts indicate that the site was a seasonal,long-lived central camp used by hunter-gatherers.In this study,6 environmental proxies recorded in sediment cores of Qinghai Lake are selected from reconstruct the environmental indexes?EI?of Qinghai Lake basin during the early Holocene,the EI shows a fluctuating upward trend,and suggesting an improvement of environmental conditions,which is the primary driving force for the early foragers colonized at the Qinghai Lake basin.?2?The OSL dating results and distribution of stones artifacts from ELH-3stratigraphic profile revealed that prehistoric human activities were frequently occurred in the Eling Lake area during the middle Holocene,and the prehistoric humans were follow the pattern of“high-low elevation”seasonal migration.The concentration of charcoal particles were increased significantly in the period of 4.2³.2 ka BP,which suggest the intensification of human activities in the Eling Lake area during this period.Meanwhile,during this stage the pollen content of Aster-type and Artemisia have increased significantly and grain size of the sediment is relatively small.,which indicate the alpine steppe developed in the Eling Lake area under a relatively mild climatic conditions.The concentration of coprophilous fungal spore increased at 1.2¹.0 ka BP,which indicate the increase of regional pastrolism.With the transition of subsistence stratigy from hunting-gathering to nomadic economy,the deterioration of the climate is no longer prevent the ancient peoples penatrate into hinterland of the higher altitude regions of Qinghai-Tibetan Plateau.?3?Since the Last Deglaciation to early Holocene,the improvement of the natural environment promoted prehistoric humans to march into the Qinghai Lake Basin at an altitude of about 3000 m.The TX-3-1 site is the imprint of prehistoric human activity in low altitude areas after the improvement of climatic conditions.After the Holocene Optimum Period,microlithic hunters began to expand to the plateau hinterland above 4000m,and the human activity at the ELH-3 significantly intensified in the period of 4.2³.2 ka BP;During late Holocene,the subsistence stratigy of the ancient human transformed from hunting-gathering to nomadic pastoralism,which promoted peoples to overcome the climate deterioration on the Qinghai-Tibetan Plateau.