地震地质 ›› 2023, Vol. 45 ›› Issue (5): 1041-1056.DOI: 10.3969/j.issn.0253-4967.2023.05.001

• 研究论文 • 上一篇    下一篇

早更新世地层ESR法测年可靠性研究——以靖远剖面为例

魏传义1)(), 尹功明1), 王旭龙2), 王度2,3), 姬昊1), 刘春茹1), 李新秀1)   

  1. 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
  • 收稿日期:2022-11-07 修回日期:2023-04-01 出版日期:2023-11-23 发布日期:2023-11-23
  • 作者简介:

    魏传义, 男, 1990年生, 2019年于中国地质大学(武汉)获第四纪地质学博士学位, 副研究员, 主要从事第四纪年代学与地表过程研究, E-mail:

  • 基金资助:
    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); 中国地震局地质研究所基本科研业务专项(IGCEA2226); 第2次青藏高原综合科学考察研究(2019QZKK0901)

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

WEI Chuan-yi1)(), YIN Gong-ming1), WANG Xu-long2), WANG Duo2,3), JI Hao1), LIU Chun-ru1), LI Xin-xiu1)   

  1. 1) State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
    2) State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
    3) College of Earth Sciences, Guilin University of Technology, Guilin 541000, China
  • Received:2022-11-07 Revised:2023-04-01 Online:2023-11-23 Published:2023-11-23

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11 000Gy附加剂量范围内ESR信号未饱和, Al心在13 000Gy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。

关键词: 早更新世, 砾石层, 石英, ESR法测年, Al心, Ti-Li心

Abstract:

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 14C dating, lacking of tephra for K-Ar dating, and strict restrictions for 26Al/10Be 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 26Al/10Be 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 11 000Gy and 130 00Gy additional gamma ray dose, respectively; combined with the long thermal lifetimes of the quartz Ti-Li center(8×106a)and Al center(7.4×109a), 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 goodness is greater than 0.98.

(3)The average ESR dating results of quartz Ti-Li center and Al center of Jingyuan gravel layer is~(1.67±0.15)Ma and~(1.65±0.69)Ma, respectively, which is consistent with the previously well-known age within the error range.

To better understand the lower dating limit of the quartz ESR dating method, based on the previous analysis of the ESR signal thermal stabilities, we discuss the maximum saturation of the ESR signals and ESR signals' sensitivity. Combined with the fitting goodness evaluation of various fitting functions, we propose that the quartz Ti-Li center and Al center ESR dating method could provide reliable chronological constrains on the sand lens of early Pleistocene gravel layer. The results of our study not only provide a solid theorical foundation for the application of quartz ESR dating method for late Pliocene and early Pleistocene fluvial sediments, but also demonstrate a typical practice example of the ESR method on dating late Cenozoic sediments.

Key words: early Pleistocene, gravel layer, quartz, ESR dating, Al center, Ti-Li center