Sedimentary transformation and source-to-sink response to the Eocene rifting-detachment in the western Baiyun Sag, Pearl River Mouth Basin

Jun LIU; Guangrong PENG; Jinyun ZHENG; Song CAI; Dingwei ZHU; Ziyi WANG

doi:10.11743/ogg20230306

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Publishing Language: Chinese

Sedimentary transformation and source-to-sink response to the Eocene rifting-detachment in the western Baiyun Sag, Pearl River Mouth Basin

Jun LIU^{¹^,²}(), Guangrong PENG^{¹^,²}, Jinyun ZHENG^{¹^,²}, Song CAI^{¹^,²}, Dingwei ZHU^{¹^,²}, Ziyi WANG^{¹^,²}

Shenzhen Branch of CNOOC, Shenzhen, Guangdong 518000, China

Deepwater Development Ltd. , CNOOC, Shenzhen, Guangdong 518000, China

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Abstract

During the Eocene rifting period, the Pearl River Mouth Basin (PRMB) was in an alternating pattern of uplift and depression. The transition of tectonic activity from brittle rifting to ductile detachment in the deep water area of the continental margin is mostly manifested as the change of sag from deep to shallow and the migration of depositional center. However, the lack of discussion on the sedimentary responses in the depression has restricted the prediction of the distribution of sedimentary bodies formed in the process of transition. The study serves to restore the sedimentary palaeogeomorphology during the Eocene rifting and detachment periods based on the drilling and 3D seismic data of full coverage in the western Baiyun Sag, PRMB. The results are shown as follows. First, during the rifting period, the lacustrine basins were narrow and deep, generally with multiple depositional centers developed, while during the detachment period, the lacustrine basins were wide and gentle, with water converging toward the detachment center. Second, combined with well-tied seismic interpretation of depositional framework and seismic calibration of depositional configuration, it is believed that minor-axis provenances existed in the western Baiyun Sag due to the control of pre-existing fault blocks, leading to the development of fan delta, semi-deep lake and braided river delta (fan/braid) depositional systems during the rifting period; while during the detachment period, as a result of ductile uplifting, the overall terrain slope got lowered (＜10°), the water body got shallowed and the range of high-energy water body expanded. Major-axis provenances appeared in the uplifted zone, and braided river delta-beach bar (beach/fan) depositional systems were widely developed within the structural lows. Third, the coupling of drainage zoning parameters in Panyu low uplift area reveals that the sediment supply efficiency of beach/fan sedimentary systems was high, with an increasing proportion of sand in the sediments, and the sedimentary system developed in the major-axix direction of the ductile uplift zone can form a favorable source-reservoir configuration.

Keywords

rifting-detachment transformation sedimentary landform restoration source-to-sink system Eocene Baiyun Sag Pearl River Mouth Basin (PRMB)

CLC number: TE121.2 Document code: A Article ID: 0253-9985(2023)03-0600-13

References

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REN Jianye, PANG Xiong, LEI Chao, et al. Ocean and continent transition in passive continental margins and analysis of lithospheric extension and breakup process: Implication for research of the deepwater basins in the continental margins of South China Sea[J]. Earth Science Frontiers, 2015, 22(1): 102-114.