早更新世地层ESR法测年可靠性研究——以靖远剖面为例  

RELIABILITY EVALUATION OF QUARTZ ESR DATING METHOD ON EARLY PLEISTOCENE SEDIMENT:A CASE STUDY OF JINGYUAN SECTION

作　　者：魏传义[1] 尹功明[1] 王旭龙[2] 王度 姬昊 刘春茹[1] 李新秀 WEI Chuan-yi;YIN Gong-ming;WANG Xu-long;WANG Duo;JI Hao;LIU Chun-ru;LI Xin-xiu(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences,Xi′an 710061,China;College of Earth Sciences,Guilin University of Technology,Guilin 541000,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [2]中国科学院地球环境研究所,黄土与第四纪地质国家重点实验室,西安710061 [3]桂林理工大学,地球科学学院,桂林541000

出　　处：《地震地质》2023年第5期1041-1056,共16页Seismology and Geology

基　　金：国家自然科学基金(42002203);中国地震局地质研究所基本科研业务专项(IGCEA2208,IGCEA2226);第2次青藏高原综合科学考察研究(2019QZKK0901)共同资助。

摘　　要：第四纪碎屑沉积物是新构造运动和第四纪地质环境变化的重要信息载体。对第四纪碎屑沉积物,尤其是对距今200ka以上不含火山灰的粗颗粒样品(如砾石堆积)进行测年,一直是第四纪年代学研究中的重点和难点问题,石英ESR测年法是能够直接测定这类样品的测年方法之一。但是,将石英ESR法测年应用于早更新世沉积物(特别是粗颗粒沉积)结果的可靠性国内外至今鲜有报道,是目前亟待解决的年代学问题之一。文中基于石英ESR法测年原理和前人的研究成果,以已知年龄的下更新统靖远砾石层为研究对象,探讨了早更新世砾石堆积石英ESR法测年的可靠性。结果显示:1)靖远砾石层石英Ti-Li心在11000Gy附加剂量范围内ESR信号未饱和,Al心在13000Gy附加剂量范围内ESR信号未饱和;2)单饱和指数函数和“指数+线性”函数可分别为Ti-Li心和Al心提供更优的等效剂量拟合结果,且拟合效果均优于0.98;3)靖远砾石层石英Ti-Li心和Al心的平均ESR测年结果分别为(1.67±0.15)Ma和(1.65±0.69)Ma,与已知的宇生核素测年结果(约为(1.73±0.13)Ma)和岩石地层结果在误差范围内是一致的。综上所述,石英Ti-Li心和Al心ESR法测年均可为早更新世含砂质透镜体的砾石层堆积提供可靠的年代学数据。As the most recent period of the geological record,the Quaternary climate change,tectonics and river drainage evolution have been well recorded by Quaternary sediment.Establishing the timing of these geological changes,and of their effects on the earth s environment,is a key element in Quaternary research.Because of dating range limit of quartz OSL dating and^(14)C dating,lacking of tephra for K-Ar dating,and strict restrictions for^(26)Al/^(10)Be cosmogenic nuclide dating,the samples older than 200ka were critical but difficult in Quaternary dating,while electron spin resonance(ESR)dating method could provide absolute age for late Pliocene and Pleistocene samples.Previous studies show that quartz Al center and Ti-Li center are the most suitable signals for sediment ESR dating,and have been successfully applied into middle-late Pleistocene sediment dating.However,the application of those two centers ESR chronology into early Pleistocene or pre-Quaternary sediment remains confusion.In this study,early Pleistocene Jingyuan gravel layer sediment deposited at Yellow river were collected for ESR dating.The results of comprehensive comparative analysis of high resolution magneto-stratigraphy and deep-sea oxygen isotope curve of loess-paleosol sequences and high credible^(26)Al/^(10)Be cosmogenic nuclide dating age make the Jingyuan gravel layer as the ideal material to evaluate the dating range,especially lower dating range,of the quartz Ti-Li center and Al center,respectively.The results show that:(1)The quartz Ti-Li center and Al center signal intensity of Jingyuan gravel layer was not saturated within 11000Gy and 13000Gy additional gamma ray dose,respectively;combined with the long thermal lifetimes of the quartz Ti-Li center(8×10^(6)a)and Al center(7.4×10^(9)a),guarantee the ESR dating range for million years.(2)The single saturation exponential function and“EXP+LIN”functions could provide more accuracy fitting result of equivalent dose of quartz Ti-Li center and Al center,respectively,and the fitting goodnes

关 键 词：早更新世 砾石层 石英 ESR法测年 Al心 Ti-Li心 

分 类 号：P597[天文地球—地球化学]