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干旱区地理 ›› 2022, Vol. 45 ›› Issue (6): 1773-1783.doi: 10.12118/j.issn.1000-6060.2022.051

• 地表过程研究 • 上一篇    下一篇

巴丹吉林沙漠晚更新世沉积物矿物学特征及其指示意义

张新毅1(),范小露1(),田明中2   

  1. 1.阜阳师范大学历史文化与旅游学院地理系,安徽 阜阳 236037
    2.中国地质大学(北京)地球科学与资源学院,北京 100083
  • 收稿日期:2022-02-12 修回日期:2022-04-21 出版日期:2022-11-25 发布日期:2023-02-01
  • 通讯作者: 范小露(1987-),女,博士,副教授,硕导,主要从事第四纪气候演化与气象灾害研究. E-mail: atsunnyshore@126.com
  • 作者简介:张新毅(1989-),男,硕士,工程师,主要从事沉积学及灾害地质学研究. E-mail: xinyiz0117@163.com
  • 基金资助:
    安徽省哲学社会科学规划项目(AHSKQ2021D213);安徽省高校科学研究项目重点项目(SK2020A0311);安徽省高校科学研究项目重点项目(SK2021A0416);阜阳师范大学青年人才基金重点项目(rcxm201907)

Mineralogical characteristics and its significance of late Pleistocene sediments in the Badain Jaran Desert

ZHANG Xinyi1(),FAN Xiaolu1(),TIAN Mingzhong2   

  1. 1. School of History Culture and Tourism, Fuyang Normal University, Fuyang 236037, Anhui, China
    2. School of the Earth Science and Resources, China University of Geoscience, Beijing 100083, China
  • Received:2022-02-12 Revised:2022-04-21 Online:2022-11-25 Published:2023-02-01
  • Contact: Xiaolu FAN

摘要:

巴丹吉林沙漠是研究亚洲内陆干旱化等古环境问题的重要窗口。以沙漠东南缘巴润宝日陶勒盖剖面为研究对象,通过详细的薄片矿物学、X射线衍射半定量及粒度等方法指标,综合分析沉积物的结构成熟度和成分成熟度等矿物学特征,恢复该地区在晚更新世沉积环境变化。结果表明:(1) 66.8 ka之前沉积的矿物碎屑分选性好、磨圆较好,稳定矿物含量高;66.8 ka之后,矿物分选性差、磨圆差,稳定矿物含量均下降,粘土矿物增加。(2) 66.8 ka之前沉积物以中砂为主,66.8 ka之后以细砂为主。研究表明巴丹吉林沙漠东南缘66.8 ka前后存在一次沉积环境突变,由风沙沉积转变为湖相沉积,可能代表了一次典型的东亚夏季风增强事件,推测与低纬西太平洋温度升高相关。对于巴丹吉林沙漠东南缘沉积物矿物学的相关认知有助于理解沙漠中沉积环境的转换过程及其驱动因子,并为重建沙漠千年尺度的古环境与古气候演变提供数据参考。

关键词: 晚更新世, 矿物特征, 沉积环境, 巴丹吉林沙漠

Abstract:

The Badain Jaran Desert, Inner Mongolia, China is an important window to study the aridity and other paleoenvironmental problems in Asia. Taking the Barunbori Tolgoi section in the southeastern margin of the desert as the research object, mineralogical characteristics of sediments, such as structural and compositional maturity, were thoroughly analyzed. Through detailed sample mineralogy under a microscope, semi-quantitative X-ray diffraction (XRD) test, and grain size analysis, the sedimentary environment in this area during the late Pleistocene was reconstructed. Microscopic characteristics of sediments indicate that the mineral debris deposited before 66.8 ka had good sorting, high roundness, and high stable mineral contents, indicating high structural and compositional maturity. After 66.8 ka, the mineral debris exhibited poor sorting, low roundness, and low stable mineral contents, whereas the number of clay minerals increased, indicating lower structural and compositional maturity. The XRD results show that the sediments before 66.8 ka were dominated by felsic minerals with a percentage of 95%-100%. After 66.8 ka, the number of clay minerals gradually increased, indicating that the environment was relatively warm and humid. The appearance of carbonate and evaporite minerals in the later period indicated that the lake water developed toward the direction of salinity. The grain size analysis results show that the sediments before 66.8 ka are dominated by medium sand, with an average content of 65.33%. After 66.8 ka, the sand becomes fine, with the content ranging from 56.32% to 61.51%. The mineral-sorting coefficient corresponding to the standard deviation of grain size data shows that the sorting coefficient of the sediments before 66.8 ka is 0.40-0.67, indicating good sorting. After 66.8 ka, the sediment-sorting coefficients ranged from 0.55 to 1.03, indicating poor sorting. The results show that there was a sudden sedimentary environment change from aeolian sediments to lacustrine sediments around 66.8 ka in the southeastern margin of the Badain Jaran Desert, indicating a significant increase in the lake area and water level. According to the macroscopic geomorphological characteristics and measured data in the field, the elevation of the two salt lakes on the west side of the Barunbori Tolgoi section is approximately 1275 m, whereas the elevation of the platform on the top of the section is 1294 m, which means that the water level rose at least 19 m during this period. The lacustrine platform was gradually deposited on the underlying dunes during the long lake period. The sedimentary environment change may represent a typical East Asian summer monsoon intensification event, which is speculated to be related to the warming of the low-latitude western Pacific Ocean.

Key words: late Pleistocene, mineral characteristics, depositional environment, Badain Jaran Desert