Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (4): 19-42.DOI: 10.13745/j.esf.sf.2022.10.18

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The paleotectonic and paleogeography reconstructions of the Tarim Basin in the Neoproterozoic and prediction of favorable deep source rock areas

HE Bizhu1,2(), JIAO Cunli3, LIU Ruohan1,4, CAO Zicheng5, CAI Zhihui1, LAN Mingjie5, YUN Xiaorui1,3, ZHU Ding5, JIANG Zhongzheng5, YANG Yujie5, LI Zhenyu1,6   

  1. 1. Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
    2. Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
    3. Exploration and Production Research Institute of SINOPEC, Beijing 100083, China
    4. PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China
    5. Institute of Northwestern Petroleum Subsidiary of SINOPEC, ürümqi 830011, China
    6. China University of Geosciences (Beijing), Beijing 100083, China
  • Received:2022-08-20 Revised:2022-09-29 Online:2023-07-25 Published:2023-07-07

Abstract:

The tectono-sedimentary development of the Neoproterozoic of the Tarim Basin is important for understanding the basin initiation process and for the regional ultra-deep/deep oil and gas exploration. Due to the deep burial and data scarcity, it is extremely difficult to research the deep buried areas of the basin, and data interpretation can be ambiguous. This study, based on comprehensive analyses of drilling data and newly reprocessed seismic reflection data collected across the basin, reveals that the Tarim Basin experienced at least three tectonic cycles during the Neoproterozoic and developed three super stratigraphic sequences and 7-9 stratigraphic sequences. The distribution of sedimentary facies of the Neoproterozoic in the basin and its margin vary greatly, constrained obviously by Neoproterozoic rift depressions. The basin developed shelf facies, glacier facies, basin facies, carbonate platform facies, tidal-flat facies, fan-delta facies, littoral and shallow sea facies, alluvial-fluvial facies, and igneous rock facies. Results on the structural architecture and spatial distribution of unconformities during the Cryogenian-Early Cambrian reveal that the tectono-sedimentary frameworks of the basin margin and deep buried area are formed in an extensional environment. The main unconformity types include angular unconformity with low-angle and monocline structures, progressive syntectonic angular unconformity, fault-controlled unconformity, and paraconformity, and they are observed in every rift depressions and at different locations. The paleotectonic and paleogeography of the basin before the deposition of the Ediacaran and the Cambrian are reconstructed based on sequence stratigraphy, Neoproterozoic fault activity, unconformity architecture, seismic stratigraphy, and wave impedance inversion property data, which show that the distribution of various sedimentary facies zones is related to the developments of rift depressions and subsidence centers and the differences of structural deformations. In response to the subduction-related outgrowth and the breakup of Rodinia, and the assembly of Gondwana, the Tarim Basin experienced three evolutionary cycles in the Neoproterozoic: initiation of deep rift depressions (900-760 Ma), development of deep rift depressions (~750-630 Ma), and rapid extensions and declining of rift depressions (630-520 Ma). Correspondingly, the Tarim block underwent subduction-related back-arc extension, continental rift, and passive continental margin transformations during the Neoproterozoic. The Ediacaran to Cambrian transition is an important period where the Tarim block transformed from continental-rift/rift-depression basins into a unified cratonic basin. This is evidenced by the unconformity between the Cambrian and the Ediacaran or pre-Ediacaran across the basin and covered by the Lower Cambrian further. Here, a new method is developed to reconstruct paleotectonic and paleogeographic history of deep buried basins based on structural and multi-attribute analyses. Besides, the favorable development areas of Lower Cambrian-Upper Cryogenian source rocks are predicted according to structural and sedimentary facies constrains, which has great significance for the evaluation of deep oil and gas resource potential in the basin.

Key words: sequence stratigraphy, structural architectures of unconformities, paleotectonics and paleogeography, multiphase transformation, Neoproterozoic, Tarim Basin

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