Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (3): 441-451.DOI: 10.13745/j.esf.sf.2022.9.9

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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

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

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