Aeolian Sediment And Environmental Evolution Since Last Deglaciation Period In The West Bank Of Qinghai Lake Revealed By A High Resolution OSL Dating

With the implementation of the global change research program in the past,inversion of the paleoenvironment has become an important way to predict future climate change.Compared with the climatic conditions in the last glacial period,the Holocene climatic conditions are similar to the present,and it is possible to reappear in the future.It can provide a theoretical basis for predicting the future environmental conditions and proposing human adaptation strategies that to study the evolution of the Holocene environment,to understand the evolution of the past environment and to drive mechanism.Qinghai Lake,as the largest brackish lake in China,is located in the northeastern margin of the Qinghai-Tibet Plateau and situated in a climatic junction where the ASM and the westerlies interact strongly.Thus,the area is climatically sensitive for climate change and become ideally located for paleoenvironment evolution studies.The extensive development of aeolian sediments has its advantages in reconstructing the paleoenvironment.It is shown that the sample collection is simple and easy,and the environmental indicators such as grain size and other physical proxies have clear environmental meaning,and the dating reliability is high.Using the high-density optical luminescence dating can detect the continuity of the profile,can build the Millennium scale high-resolution chronology framework.Therefore,it is possible to reveal the characteristics of environmental evolution of Qinghai Lake Basin by using multi-section,high-density optical luminescence dating,which will provide a scientific basis for the sustainable development of the region.In view of the previous work on the western part of Qinghai Lake is less,we select ND profile and SNH section in the west bank of Qinghai Lake as the research object.The former is mainly composed of aeolian sand,and the letter is mainly composed of loess.We have dated the aeolian,loess and the paleosol deposit by optically stimulated luminescence(OSL)method,combined with stratigraphy and continuous environmental proxies(grain size,magnetic susceptibility,chromacity)of the sections at ND and SNH.We reconstruct the regional environmental evolution of the west bank of Qinghai Lake since the last deglaciation.On the basis of the absolute dating and variations of these climatic proxy indicators,the results show that: 1)High-density OSL dating can establish a reliable chronology framework for aeolian deposition.A reliable chronological framework of aeolian sediments since the last deglaciation is established using high resolution OSL dating,with 27 OSL ages and 1 AMS 14 C age.2)We reconstruct the process of environmental evolution in the west bank of Qinghai Lake since the deglaciation: From 12.3 to 8.4 ka BP,the paleolclimate was charactered by continuous drought,strong aeolian activity,aeolian sand accumulation.During the middle Holocene,the climate was warm and wet,the paleosol was developed.The warmest and wettest time of the middle Holocene in the Qinghai Lake area is around 5.4 ka BP.Since the late Holocene,the climate fluctuates frequently and tends to deteriorate.The profile records a cold event of 4.0 ka BP,2 ka BP and 1.3 ka BP regional effective moisture increased.3)The environmental evolution information recorded by the aeolian sediments is coupled with the existing high lake level records: low lake level appeared in early Holocene when the climate was drought,in the middle Holocene warm and wet period,the lake level reached highest,since the late Holocene,the effective moisture gradually decreased,the water level of Qinghai Lake declined.4)Through the regional comparison study,we find that the paleoclimate evolution records of the lake area,which is based on the aeolian sediments from the ND profile and SNH section,has a good comparability with the northeastern Tibetan-Plateau or global climate events.