Preprints
https://doi.org/10.5194/se-2021-92
https://doi.org/10.5194/se-2021-92

  19 Jul 2021

19 Jul 2021

Review status: this preprint is currently under review for the journal SE.

Impact of basement thrust fault on low-angle normal fault and rift basin evolution: a case study in the Enping sag, Pearl River Mouth Basin

Chao Deng1, Rixiang Zhu2,1, Jianhui Han3, Yu Shu4, Yuxiang Wu4, Kefeng Hou5, and Wei Long3 Chao Deng et al.
  • 1State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China
  • 2Beitucheng West Road, Institute of Geology and Geophysics, Chinese Academy of Sciences, Chaoyang District, Beijing, 100029, China
  • 3College of Energy, Chengdu University of Technology, Chengdu, Sichuan 610059, China
  • 4Shenzhen Branch Company of CNOOC, Shenzhen, China
  • 5Changqing Oil Field, PetroChina Company Limited, CNPC, Xi’an, 710021, China

Abstract. Reactivation of pre-existing structures and their influence on subsequent rift evolution have been extensively analysed in previous researches on rifts that experienced multiple phases of rifting, where pre-existing structures were deemed to affect nucleation, density, strike direction and displacement of newly-formed normal faults during later rifting stage. However, previous studies paid less attention to the extensional structures superimposing on an earlier compressional background, leading to a lack of understanding, e.g., reactivation and growth pattern of pre-existing thrust fault as low-angle normal fault, and impact of pre-existing thrust fault on newly-formed high-angle faults and subsequent rift structure. This study investigating the spatial relationship between intrabasement thrust and rift-related faults in the Enping sag, northern South China Sea, indicates that the rift system is built on the previously deformed basement with pervasive thrusting structures, and that the low-angle major fault of the study area results from reactivation of intrabasement thrust fault. In addition, reactivated basement thrust fault can affect the nucleation and dip of nearby new faults, cause new faults to nucleate at or merge into it in vertical, and finally generate typical fault interactions, i.e., merging, abutting and crosscutting faults. This work not only provides insights into understanding growth pattern of rift-related faults interacting with reactivated low-angle faults, but also has broader implications on how basement thrust faults influence rift structure, normal fault evolution and syn-rift stratigraphy.

Chao Deng et al.

Status: open (until 31 Aug 2021)

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Chao Deng et al.

Chao Deng et al.

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Short summary
This study uses seismic reflection data to interpret the geometric relationship and evolution of intrabasement and rift-related structures in the Enping sag, the northern South China Sea. Our observations suggest primary control of pre-existing thrust fault on formation of low-angle normal fault, with possible help of low-friction materials, and significant role of pre-existing basement thrust fault on fault geometry, paleotopography and syn-rift stratigraphy of rift basin.