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中国沙漠 ›› 2023, Vol. 43 ›› Issue (3): 69-85.DOI: 10.7522/j.issn.1000-694X.2022.00136

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腾格里沙漠两万年以来典型沉积物钾长石和石英光释光测年对比研究

王颖(), 弋双文(), 徐志伟, 张昊辰, 李徐生   

  1. 南京大学 地理与海洋科学学院,江苏 南京 210000
  • 收稿日期:2022-08-31 修回日期:2022-11-10 出版日期:2023-05-20 发布日期:2023-05-31
  • 通讯作者: 弋双文
  • 作者简介:弋双文(E-mail: ysw7563@nju.edu.cn
    王颖(2000—),女,江苏盐城人,硕士研究生,研究方向为光释光年代学。E-mail: mg21270024@smail.nju.edu.cn
  • 基金资助:
    国家自然科学基金项目(42122001);中国科学院“西部之光”交叉团队项目;中央高校基本科研业务费项目(0209-14380091)

Quartz OSL and K-feldspar pIRIR dating of typical sediments over the past 20 000 years from the Tengger Desert, northern China

Ying Wang(), Shuangwen Yi(), Zhiwei Xu, Haochen Zhang, Xusheng Li   

  1. School of Geography and Ocean Sciences,Nanjing University,Nanjing 210000,China
  • Received:2022-08-31 Revised:2022-11-10 Online:2023-05-20 Published:2023-05-31
  • Contact: Shuangwen Yi

摘要:

沙漠内部保存的晚第四纪沉积序列,是重建过去气候环境变化的重要材料。近年来,不同测年方法被用于测定风成、湖相等各类沉积物的年龄,特别是光释光测年技术在沙漠地区的应用越来越多。然而,对不同光释光测年技术能否获得相对年轻样品的可靠年龄等问题,仍存在一些不确定性。本研究在腾格里沙漠不同点位采集了沉积物样品,开展了石英单片再生剂量法(SAR-OSL)和钾长石红外后释光法(pIRIR150)对比测试,尤其是针对钾长石pIRIR150进行了剂量恢复实验、衰退系数(g-值)以及残余剂量测定,进而探究钾长石pIRIR150技术在该地区沉积物测年中的适用性与可靠性。结果表明:钾长石pIRIR150释光信号总体晒退良好,30 h晒退后的残余剂量仅为0.07~0.27 Gy,并且在60 Gy的剂量范围内(对应研究区约两万年以内的样品),剂量恢复比率基本为1。经g-值校正后的钾长石pIRIR150年代结果总体上出现高估,而未校正的年代则与石英SAR-OSL年代结果具有较好的一致性,表明研究区沉积物样品的g-值校正可能存在一定的不确定性。在建立年代控制的基础上,本文发现不同点位重建的局地地貌格局变化具有强烈的异质性,但在冰期-间冰期尺度上,与大范围的气候环境格局变化基本一致。在末次盛冰期及冰消期,沙丘活跃,植被退化,湖泊和绿洲面积相对缩小;而在早中全新世,沙丘流动性减弱,植被增多,湖泊和绿洲面积相对扩大。过去几百年以来,不同点位的沙丘也经历了多次活化与固定的转换,这与局地的环境变化和其他扰动等因素有关。

关键词: 光释光测年, pIRIR150, 地貌格局重建, 风沙环境变化, 腾格里沙漠

Abstract:

Sedimentary records of the late Quaternary preserved in the deserts are important archives to reconstruct the paleoclimate and paleoenvironmental change. In recent years, different dating methods have been used to establish chronologies of aeolian and lacustrine sediments in the deserts, especially the Optically Stimulated Luminescence (OSL) dating technology. However, it still has some uncertainties whether the luminescence dating techniques could provide reliable ages for relatively young samples. In this study, several sediments were collected from different sites in the Tengger Desert, and their ages were measured by quartz SAR-OSL and K-feldspar pIRIR150 dating methods. A set of tests, such as the dose recovery, fading and residual tests, were carried out to explore the applicability and reliability of the K-feldspar pIRIR150 dating protocol in this area. The results suggest that the K-feldspar samples were well bleached before deposition. Residual doses of pIRIR signals are between 0.07-0.27 Gy and the dose recovery ratio is basically equal to 1 within the dose range of 60 Gy (equal to about 20,000 years). The corrected K-feldspar pIRIR150 ages are generally overestimated, while the uncorrected pIRIR150 ages are in good agreement with the quartz SAR-OSL ages, indicating the uncertainties of g-value correction. Based on the quartz SAR-OSL and K-feldspar pIRIR150 ages, it is found that the geomorphological evolution at different sites in the study area show strong heterogeneity at local scales, while at glacial-interglacial time scales, their changes are broadly consistent with regional climatic changes. During the Last Glacial Maximum and Deglacial period, the dunes were mostly active and vegetation was degraded, and the areas of lakes and oases were relatively decreased. In contrast, dune activity was restricted and vegetation coverage was increased during the Early and Middle Holocene, and the lakes and oases were relatively expanded. During the past few hundreds of years, different sites in the Tengger Desert have probably undergone multiple phases of dune activation and stabilization, which may be related to not only regional environmental changes but also local disturbances.

Key words: OSL dating, K-feldspar pIRIR150 dating, geomorphological reconstruction, aeolian environmental change, Tengger Desert

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