Single-particle Optical Luminescence Dating Of Glacial Sediments In The Yuzhu Peak Area Of Kunlun Mountains

The study of the temporal and spatial evolution history,activity law and mechanism of quaternary glaciers can better predict the evolution trend of glaciers in the future,provide scientific basis for water resources utilization and ecological environment protection,and provide key information support for modern glacier management and utilization.The determination of the age of glaciation is fundamental to the study of quaternary glaciers,and the establishment of an accurate chronology framework is the key and difficult point in the study of Quaternary glaciers,as well as the basis for the reconstruction of the temporal and spatial evolution of glaciers.The comprehensive application of various dating techniques is the key to obtain a reliable chronology framework of quaternary glaciers.Many research results show that optically Stimulated luminescence（OSL）is an ideal method for dating quaternary sediments.Glacier sedimentary environment is considered to be the most challenging environment for the application of OSL due to incomplete precipitation of sediments.In this study,the Yuzhu peak area of Kunlun Mountain in the northeast of The Tibetan Plateau was selected as the research site,and the applicability of optically dating for different types of glacial sediments was studied by using single-particle optically technology,in order to investigate the zeroing degree and luminescence characteristics of single-particle optically signals for different types of glacial sediments.In this paper,the equivalent dose（D_e）measurements of coarse grains（180-250μm）of quartz and potash feldspar from 16 different types of glacial sediments have been carried out by using single-particle OSL dating method.Based on the median age model and the minimum age model,the study of single-grain potash feldspar was compared with the previous single-piece and ¹⁰Be age results.Based on the above research,the applicability of single grain quartz and potassium feldspar in glacial sediments was preliminarily discussed.In addition,the environmental dose rate is a very important part of photoluminescence dating,which affects the accuracy of the results of photoluminescence dating.In order to test whether RGS-19A NaIγspectrometer is suitable for environmental dose-rate determination of optically stimulated luminescence dating of different types of sediments,36 samples were selected for study.The RGS-19A NaIγspectrometer was calibrated by using U,Th and K standard samples provided by Ris?Nutech of Denmark.Based on the above research contents,the main conclusions of this study are as follows:（1）Based on a series of experimental results of luminescence signal characteristics（heat transfer,growth curve,decline curve,preheating plateau,cycle ratio）,residual dose and dose recovery,the single-particle method is suitable for the luminescence dating of glacial sediments in the Kunlun Yuzhu peak region in the northeast of the Tibetan Plateau.（2）The photoluminescence sensitivity of quartz mineral particles in this area is low,the photoluminescence signal is dim,and the luminescence efficiency is low,so it is difficult to be used for the test of single particle equivalent dose.Compared with single quartz,the average proportion of measured potassium feldspar particles accepted by the screening criteria is about 30%,the average OD value of the samples is 67%,and the range is 37%-98%,indicating that most of the samples have the problem of incomplete sun degradation.The results of single particle potassium feldspar measurement in modern glacial and glacial sediments show that the inherent residual dose is～70Gy and～5Gy.（3）The median model dating results of four single grain k feldspar samples（YZN101/102/111/112）collected on the first moraine dam nearest the modern glacier developed on the Northern Slope of Yuzhu Glacier are similar to those of single quartz（14.3±1.0 ka to 18.5±2.0 within the error range Ka）,the minimum age model of the four samples is～3ka,which is consistent with the previous observation that the moraine dam was developed in the New Glacial age based on geomorphology assessment,which further demonstrates the reliability of p IRIR age results of single-grain potash feldspar.The application of p IRIR luminescence dating method of single-grain potash feldspar to the dating results of glacial sediments in Yuzhu peak shows that single-grain luminescence dating method has good applicability to the dating of glacial sediments.To a certain extent,accurate chronological results of moraine dam development can be obtained,which has good potential for future application.（4）The environmental dose rates of different types of sediments in the late Quaternary were measured by NaIγspectroscopy.The results showed that for most of the samples,NaIγspectroscopy was consistent with ICP-MS and NAA measurements within the error range（±1σ）,and the average dose rate ratio was 1.13±0.03（n=36）.For samples with uniform lithology,NaIγspectrometer,ICP-MS and NAA can obtain accurate results.The NaIγspectrometer can provide more accurate measurements for samples with heterogeneous lithology,such as mixed accumulations of glacier and river sediments.Therefore,Ris?NaIγspectrometer can be widely used for environmental dose-rate measurement of different types of sediment by optically stimulated luminescence.