石英Al心和Ti-Li心电子自旋共振信号测年结果对比:以腾格里沙漠白碱湖地区BJ14钻孔中沉积物为例  

Comparison of the electron spin resonance(ESR) dating results between Al signals and Ti-Li signals in quartz grains: a case from sediments of BJ14 core drilled from the Baijian Lake in the Tengger Desert

作　　者：李振军 牟雪松 范育新 LI Zhenjun;MOU Xuesong;FAN Yuxin(Key Laboratory of Mineral Resources in Western China(Gansu Province),School of Earth Sciences,Lanzhou University,Lanzhou 730000,China;Key Laboratory of Western China’s Environmental Systems(Ministry of Education),Lanzhou University,Lanzhou 730000,China)

机构地区：[1]兰州大学地质科学与矿产资源学院,甘肃省西部矿产资源重点实验室,兰州730000 [2]兰州大学西部环境教育部重点实验室,兰州730000

出　　处：《地球环境学报》2018年第6期589-598,共10页Journal of Earth Environment

基　　金：国家自然科学基金项目(41772169);中央高校基本科研业务费项目(Lzujbky-2018-it21)

摘　　要：早—中更新世沉积年代的确定是第四纪研究领域亟待解决的难题,电子自旋共振(ESR)测年法为该时段沉积物定年提供了可能。但已有的研究发现:石英Ti心和Al心ESR信号完全衰退"回零"或达到较稳定"残留"所需时间较长,因而其可信性备受质疑。本研究选取腾格里沙漠白碱湖地区BJ14钻孔中5个不同深度的沉积物,分别基于其中石英Ti心和Al心信号进行了ESR定年。测年结果显示:(1)2个样品基于Al心ESR信号与基于Ti-Li心ESR信号的测年结果在年龄误差范围内一致,其它3个样品Al心ESR测年结果较Ti-Li心测年结果偏老200 — 500 ka;(2)与该孔的古地磁测年结果对比表明,石英Ti-Li心ESR测年结果相对可靠。上述研究结果表明石英Ti-Li心的ESR测年结果至少能提供中更新世更为可信的沉积年龄。Background,aim,and scope The determination of the depositional age of Early to Middle Pleistocene is an urgent problem for Quaternary studies,the ESR dating method provides the possibility for the dating of sediments during this period.However,previous works have found that it takes a long time for the signal associated with the titanium(Ti)and aluminum(Al)defects in detrital quartz grains to be reduced to zero or to constant residual value by sunlight exposure,which may cause the phenomenon that the ESR signals of quartz grains is incomplete bleaching prior to sediment deposition.On the other hand,when using ESR signal of quartz for dating,it is difficult to accurately determine whether the ESR signal has been reset to its constant residual value or to zero,moreover,the constant residual value of ESR signal for Al center is difficult to be estimated accurately.Therefore,the reliability by this method remains to be questioned.In this paper,we attempt to identify the best agreement between other age criteria established by paleomagnetic dating study with observed age and to determine whether ESR dating is reliable.Materials and methods Here we carried out ESR analyses on five samples with different depths from the BJ14 core drilled from the Baijian Lake in the present Tengger Desert based on Ti-Li signal and Al signal in detrital quartz grains.Results Our results show that:(1)this method yields agreement between the Al signal and Ti-Li signal ages for 2 samples,while Al signal ages were 200-500 ka older than Ti-Li signal ages for other 3 samples;(2)the dates obtained by this method based on Ti-Li signal are generally consistent with paleomagnetic dating results from BJ14 core and therefore appear to be reliable.Discussion The fact that the Al signal age is older than Ti-Li signal age is probably related to the previous recognition given Al center signal slower bleaching kinetics in comparison with the Ti center.In desert environment,the process of migration or accumulation for aeolian sand is rapid,for which ESR s

关 键 词：ESR测年 Al心 Ti-Li心 腾格里沙漠 

分 类 号：P597.3[天文地球—地球化学] P512.2[天文地球—地质学]