Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (5): 161-175.DOI: 10.13745/j.esf.sf.2021.9.24

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Fault response to the Huizhou Movement in the Pearl River Mouth Basin: Insights from a case study of the Eastern Yangjiang Sag

ZHANG Xiangtao1(), PENG Guangrong1, WANG Guangzeng2,3,*(), LIU Xinying2, ZHAO Li4, YANG Yue2, ZHAN Huawang2, YU Haiyang2, MA Xiaoqian2, LI Sanzhong2,3   

  1. 1. Shenzhen Branch, CNOOC China Limited, Shenzhen 518000, China
    2. Key Lab of Submarine Geosciences and Prospecting Techniques, MOE and College of Marine Geosciences, Ocean University of China, Qingdao 266100, China
    3. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266100, China
    4. College of Resources and Environment, Shandong Agriculture University, Tai'an 271018, China
  • Received:2021-04-26 Revised:2021-05-13 Online:2022-09-25 Published:2022-08-24
  • Contact: WANG Guangzeng

Abstract:

The Huizhou Movement is a newly-defined tectonic movement occurring to the Pearl River Mouth Basin during the transition period between the early and late Wenchang rifting stages. This movement is well-responded in the Zhu Ⅰ Depression of the basin, however, its impact and response characteristics in other depressions of the basin are not known. Taking the fault system of the Eastern Yangjiang Sag, Zhu Ⅲ Depression as an example, this paper first studies the geometry and kinematic characteristics of the fault system, then summarizes its response characteristics to the Huizhou Movement in terms of its preferential orientation, assemblage style, and activity and activity migration patterns. It was found that mainly NE-NEE- and EW-NWW-trending faults of different scales develop in the Paleogene strata of the Eastern Yangjiang Sag, and their formation and evolution are mainly dominated by the pre-existing fabrics/weaknesses and regional tectonic movements. The pre-existing fabrics/weaknesses determine the preferential position, array style and general orientation of the main fault belts, imparting a favorable structural condition for the formation of various later structures along the fault belts. In the Eastern Yangjiang Sag, it is the reactivation of the pre-Cenozoic left-stepping echelon array branches of the NW-trending Yangjiang-Yitong'ansha Fault Zone that leads to the formation of a series of small strike-slip pull-apart basins along the Yangjiang-Yitong'ansha Fault Zone during its sinistral motion after the Huizhou Movement. Regional tectonic movements result in structural transformation of basin's dominant fault system including both main and secondary faults. For instance, although the Paleogene fault system of the Eastern Yangjiang Sag retains the general characteristics of the pre-existing pre-Cenozoic fabrics, such as fault position, array style and orientation, its dominant fault system, like in the Zhu Ⅰ Depression, transforms from the NE-NEE-trending extensional faults in the early Wencheng deposition stage to the sub-parallel E-W-NWW-trending transtentional faults in the late Wenchang deposition stage in response to the Huizhou Movement, and fault activities also migrate from south to north and from east to west, accordingly. The consistent response of the fault system to the Huizhou Movement in the Pearl River Mouth Basin indicates the Huizhou Movement is a wide-spread tectonic movement occurring to the north margin of the South China Sea. Therefore parallel studies of fault response characteristics in different depressions of the Pearl River Mouth Basin can provide a tectonic basis for inter-depression/inter-sag comparison of the Wenchang Formation developed in isolation across the whole basin, and facilitate oil and gas exploration in the Eastern Yangjiang Sag.

Key words: Huizhou Movement, fault system, Wenchang Formation, Eastern Yangjiang Sag, Pearl River Mouth Basin

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