Luminescence Dating Of The Paleolithic Sites In The Hanjiang River Valley During Late Pleistocene

Late Pleistocene is an important period,in which human activities are active,and the origin of modern human and the change of Paleolithic technology took place.Qinling Mountain Range,which is rich in human and Paleolithic remains,is an important channel for human migration.The Hanjiang River Valley,where Paleolithic culture is rich and diverse,is one of the areas where human and Paleolithic sites were discovered earlier and extensively studied.During Early and Middle Pleistocene,Paleolithic assemblages were dominated by the southern cobble-tool industry,and the small flake-tool industry mainly appeared in Late Pleistocene.There are also blade technology here.In addition,a large number of flint remains have been found in the area.Abundant Paleolithic cultural remains and diversified Paleolithic industrial combination are of great significance for the study of Paleolithic technology and the cultural exchanges between the South and the north.The dependable ages of the Paleolithic sites,which are the basic premise of hominins research,can provide a chronological support for the study of human activities and evolution,the development of Paleolithic technology and the origin of modern human in this region.In this study,the standard quartz single-aliquot regenerative dose（SAR）-based optically stimulated luminescence（SAR-OSL）and Thermally transferred optically stimulated luminescence（TT-OSL）methods were used for dating the Late Pleistocene samples from different profile of 13 Paleolithic sites from Hanjiang River Valley.Through the comparison of OSL and TT-OSL signals,the equivalent dose（D_e）residuals of TT-OSL signals of the samples from the JGS site were corrected.Finally,the age ranges of each Paleolithic cultural layers were determined via the dating results.Combined with magnetic susceptibility,dating data and Paleolithic characteristics,the main conclusions are as follows:（1）10 Paleolithic sites in Hanzhong,Ankang and Yunxian Basins in the middle and upper reaches of the Hanjiang River are located on the second terrace of the Hanjiang River Valley,and dominated by cobble-tool industry.The OSL signals of the samples were basically saturated,and all samples were dated by TT-OSL method.The results show that the human activities of the 10 Paleolithic sites mainly occurred between 200–50 ka,corresponding to three stages of L₂,S₁ and L₁.（2）The Paleolithic sites of Huoshiwa（HSW）and Houshanpo（HSP）,located in Danjiangkou Reservoir Area of Hanjiang River Valley,are mainly dated by OSL method.And the natural signals of the samples reached saturation at appropriately 130Gy.The OSL signals of the cultural layer samples reached saturation,so the ages given could be minimum.According to dating results,the age of the culture layer of the HSW site is>50 ka,and that of the HSP site is>70 ka.Both sites are belong to the small flake-tool industry,with flint as the main raw material,which indicates that humans in Hanjiang River Valley began to use flint to process small flakes and repair small tools earlier than 50–70 ka.（3）The Jigongshan（JGS）Paleolithic site in the lower reaches of Hanjiang River Valley has two different cultural layers,namely,the upper（flake-tool industry）and lower（cobble-tool industry）cultural layers.Through the comparative analysis of OSL and TT-OSL signals for young samples,it is concluded that there is a residual dose of about 41.5 Gy in TT-OSL signal.Results showed that the age of the upper culture layer is approximately 23±2–38±3 ka,whereas that of the lower culture layer is approximately 115±9–149±9 ka.And we propose that the main part of the upper culture layer corresponds to the late MIS 3 to the early MIS 2 stages during the glacial period in L₁ unit in the Chinese loess sequence,whereas the lower culture layer corresponds to the late MIS 6 and the early MIS 5 stages during both glacial and interglacial periods in the upper L₂ and the lower S₁ units.A cultural gap of nearly 100 ka was observed between these two cultural layers;this gap is larger than what was expected.（4）In Late Pleistocene,human activities in the Hanjiang River Valley were mainly occurred in the interglacial stage of S₁（MIS 5）,and were more frequent in the stage of200–50 ka,while the human activities after 50 ka were relatively less.The Hanjiang River Valley has always been an important area for human activities and a key area for the study of human migration and evolution as well as the origin of modern human during Late Pleistocene.During Late Pleistocene,there may be a development context of cobble-tool industry,flake-tool industry and blade technology in the Han River Valley,with the trend of miniaturization,and the preference for stone tools has changed from heavy tools to light ones.Our study on the OSL age provides an accurate time axis for the development of Paleolithic industry in Hanjiang River Valley.However,based on the existing age data and the analysis of Paleolithic cultural remains,we can only establish a preliminary context of development,which can not accurately reflect the key nodes of the Paleolithic cultural transition,and need further study.