Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (3): 356-380.DOI: 10.13745/j.esf.sf.2021.6.30

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Neoproterozoic glaciations in Yecheng area, southwestern margin of the Tarim Basin

LI Wangpeng1(), LI Huili1, WANG Yi1, LIU Shaofeng2, ZHANG Zhongpei1, YANG Weili1, CAI Xiyao1, QIAN Tao3, LI Xiaojian4   

  1. 1. Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China
    2. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
    3. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
    4. School of Earth Sciences, East China University of Technology, Nanchang 330013, China
  • Received:2021-03-22 Revised:2021-06-30 Online:2022-05-25 Published:2022-04-28

Abstract:

The Neoproterozoic glacial events record significant geological information of the Snowball Earth. In the Tarim Basin Neoproterozoic outcrops are well developed along the basin margin, making it an ideal research base for studying Neoproterozoic glaciations. The age of the Neoproterozoic diamictite along the northeastern margin of the basin is constrained from a series of well developed Neoproterozoic volcanic rocks in the Quruqtagh area; however, such constraints are lacking for other basin margin areas due to infrequent reporting of chronology data, which leads to disagreements when comparing glacial events. This project selects the minimally studied Neoproterozoic diamictite along the southwestern margin of the Tarim Basin to perform a multidisciplinary, comprehensive analysis of the mineral's petrology, isotopic chronology and lithogeochemistry of the deposit so as to determine its glacial deposition characteristics and deposition time as well as to better understand the paleoclimatic weathering conditions. The Nanhua Bolong and Sinian Yutang Formations with low CIA (chemical index of alteration) values represent two distinct episodes of Neoproterozoic glaciations. Detrital zircon U-Pb chronology of the glacial deposits and adjacent beds indicate the starting time of the Bolong glaciation is later than (710±13) Ma and corresponds to the global Sturtian glaciation, and the starting time of the Yutang glaciation is no earlier than (656±18) Ma while its termination time can be constrained by the age of the top boundary of the Nanhuan System (635 Ma) or the detrital zircon U-Pb age of the overlying Sinian System Kulkark Formation (634±9) Ma, which corresponds to the global Marinoan glaciation.

Key words: diamictite, isotopic geochronology, snowball Earth, Neoproterozoic, Tarim Basin

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