| The Shuidonggou Locality 2 is one site with the largest quantities of artifacts excavated and the thickest sedimentary sequence exposed in the Shuidonggou Site group.In the past decades of years,archaeologists had carried out several large-scale excavations on this site,with many interesting scientific research results published.However,at present,the accurate ages of its cultural layers remain unclear and the paleoenvironmental changes studies on this sites are still ambiguous.In this study,the sediment sequence of SDG2 site was re-divided,and the sedimentary facies of the stratumare also re-studied on basis of grain sizeanalysis and field observation.35 optical stimulated luminescence(OSL)samples were systematically measured to acquire the accurate age frame.Firstly,the equivalent dose of the samples was measured using the single-aliquot regenerative dose(SAR)method.Secondly,U,Th and K contents and saturated water content of each samples were measured for Dose Rate calculation,and thenand the OSL ages was caculated.Based on the high-resolution OSL age data,the palaeoenvironmental changes of the site were dicussed in this study.Our conclusions are as follows:1.The sediment sequence of SDG2 site is divided into 18 layers from top to bottom,Layers 18 and 17(14.3-15.3 m)are fluvial deposits,Layer 16(13.6-14.3 m)are marsh deposits,Layers of 15-12(9.5-13.6 m)are lacustrine deposits,and Layers2-12(0.2-9.5 m)are aeolian deposits.The top layer of this site(0-0.2m)is disturbed eolian deposits.2.Preheat & Plateau experiment and dose recovery experiments were carried out firstly on the presentative samples.The results show that a preheat temperature at260° C with a cutheat at 220 °C was applied for the De determination of all samples.The single-aliquot regenerative-dose(SAR)protocol was used to determine the De value.The OSL signals of the first 0.3 s integral after early background subtraction from the following 1.7 s were used for growth curve construction.The dose rate of all samples was determined by neutron activation analysis(NAA)to measure the concentrations of uranium(U),thorium(Th)and potassium(K).The measured watercontent of samples above 12 m in depth and an assigned water content of 20% for samples below 12 m were used for dose reate calculation.Finally,dose rates were calculated using the conversion factors of Guérin and colleagues.By using the OSL age data and grain-size data,we reconstructed the paleoenvironmental change in this areas and found it rather comparable with paleoclimatic records from the Hulu Cave.In addition,we also found that for the completely bleached samples,the ages obtained from different particle size ranges are rather consistent.3.Therefore,in this study,we got the accurate high-resolution age data of of the 7cultural layer SDG2 site: CL1,20.3±1?21.95±1.73 ka BP;CL2,25.39±2.23?25.74±1.85 ka BP;CL3,25.09±1.88?27.8±1.4ka BP;CL4,28.02±2.5ka BP;CL5,27.16±2.11?29.2±2.1ka BP;CL6,31.22±2.56?44.09±3.45 ka BP;CL7,44.09±3.45?51.3±5.55 ka BP.Combining with the previous studies on artifacts,we can conclude that the human occupation in this site has been uncontiuous during the past 50 ka.4.Our results show that a pleolake was developed during MIS3a(44-25 ka BP)and which is vanished until MIS2(25-11 ka BP).The high precipitation caused by warm-humid climate during the MIS 3,as recorded by the records from the Tibetan Plateau and adjacent areas,may attribute the formation of the paleolake at this site,which provided the suitable living conditions for the Shuidonggou man. |
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