地学前缘 ›› 2023, Vol. 30 ›› Issue (3): 441-451.DOI: 10.13745/j.esf.sf.2022.9.9

• 非主题来稿选登 • 上一篇    下一篇

西澳大利亚新元古代Browne组—Hussar组旋回地层学研究

杨昆昆(), 李海燕*(), 赵汉卿, 褚润健, 刘光泓, 吴怀春, 张世红   

  1. 中国地质大学(北京) 生物地质与环境地质国家重点实验室, 北京 100083
  • 收稿日期:2022-05-10 修回日期:2022-08-16 出版日期:2023-05-25 发布日期:2023-04-27
  • 通讯作者: *李海燕(1979—),女,博士,副研究员,主要从事旋回地层学和古地磁学的研究和教学工作。E-mail: hai2216@cugb.edu.cn
  • 作者简介:杨昆昆(1994—),男,博士研究生,构造地质学专业。E-mail: ykktmac@cugb.edu.cn
  • 基金资助:
    国家自然科学基金项目(41830215);国家自然科学基金项目(41802028)

Cyclostratigraphic study of the Neoproterozoic Browne-Hussar formations in western Australia

YANG Kunkun(), LI Haiyan*(), ZHAO Hanqing, CHU Runjian, LIU Guanghong, WU Huaichun, ZHANG Shihong   

  1. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), Beijing 100083, China
  • Received:2022-05-10 Revised:2022-08-16 Online:2023-05-25 Published:2023-04-27

摘要:

旋回地层学研究目前主要集中在显生宙,对于占据地球历史绝大部分时期的前寒武纪,相关研究较为薄弱。西澳大利亚的Officer盆地具有新元古代中期(约800 Ma)良好的地层沉积记录。Lancer 1井位于Officer盆地的西部,岩心底部包含新元古代Browne组—Hussar组约750 m的连续沉积地层,岩性以砂岩和泥岩互层为主,偶见白云岩夹层,是开展前寒武纪旋回地层学研究的理想材料。本文以自然伽马测井数据作为古气候替代性指标,通过频谱分析等方法进行了旋回地层学分析,结果表明Hussar组940~1 200 m泥岩段的伽马测井数据记录了完整的米兰科维奇旋回,长偏心率、短偏心率、斜率和岁差控制的地层旋回厚度分别为34、8~10、1.8~2.7和1.2~1.4 m。以构建的长偏心率周期(405 ka)标准曲线对该泥岩段进行天文年代校准,建立了浮动天文年代标尺,估计了约800 Ma的长偏心率、短偏心率、斜率和岁差周期分别为405、127、27~34和15.2~18.1 ka。此外,根据斜率周期(27±0.7) ka计算出当时的地月距离为(362 935±1 495) km,日长为(20.56±0.2) h。这一研究将填补新元古代早—中期(约800 Ma 时期)旋回地层学研究的空白,为前寒武纪地月系统演化提供数据支持。

关键词: 新元古代, Browne组—Hussar组, 旋回地层学, 米兰科维奇旋回

Abstract:

Current cyclostratigraphic researches mainly focus on the Phanerozoic strata whilst the Precambrian era—the longest span of geological time in Earth’s history—is less studied. The Officer Basin in western Australia possesses well-preserved mid-Neoproterozoic (~800 Ma) successions. The Lancer 1 well, located in the western Officer Basin, has recovered ~750 m of continuous sedimentary strata of the Neoproterozoic Browne-Hussar formations, mainly interbeded with sandstone and mudstone and occasional dolomite, showing great promise for the cyclostratigraphic analysis. In this study, the gamma-ray logging data of the Browne-Hussar formations are used as paleoclimate proxy. Spectral analysis shows that the wavelength ratios of the cycles in the 940-1 200 m mudstone interval of the Hussar Formation correspond to the hierarchies of the Milankovitch cycles, where sedimentary cycles, defined as 34 m, 8-10 m, 1.8-2.7 m or 1.2-1.4 m thick cycles, can be interpreted to correspond respectively to the Milankovitch long-eccentricity, short-eccentricity, obliquity and precession cycles. After calibrating to the 405-ka long-eccentricity cycle, a floating astronomical timescale is established for the mudstone interval of the Hussar Formation and the periods of the four Milankovitch cycles are estimated to be 405 ka, 127 ka, 27-34 ka and 15.2-18.1 ka, respectively. Based on the obliquity period of (27±0.7) ka, the Earth-Moon distance and the length of day (LOD) are calculated to be (362 935±1 495) km and (20.56±0.2) h, respectively. These results represent the first report on climate cycles in the Early-Neoproterozoic (~800 Ma) in response to orbital forcing, which provides a key reference to elucidating the evolution of the Earth-Moon system.

Key words: Neoproterozoic, Browne-Hussar formations, cyclostratigraphy, Milankovitch cycles

中图分类号: