Rapid post-rift tectonic subsidence events in the Pearl River Mouth Basin, northern South China Sea margin

In order to study the subsidence characteristics, temporal-spatial variation, and their controlling factors of the Pearl River Mouth Basin, we have calculated and mapped 34 wells' subsidence via 1-D backstripping method, from which 12 typical wells have been selected as a sample to compare. Three typical profiles also have been chosen to compile subsidence evolution profiles by 2-D backstripping method. All wells were synthesized as the holistic subsidence of the whole basin. The results indicate that the holistic subsidence of the basin can be divided into three episodes: The first one was Eocene with the mean total subsidence rate of 85 m/Ma; the second episode was from Oligocene to Middle Miocene with the mean total subsidence rate of 146 m/Ma; and the third episode was from Late Miocene up to present, and its mean total subsidence rate was 104 m/Ma. It is a common phenomenon that variation of subsidence and evolution existing in different units during the same period as well as different periods in the same unit. According to the distribution of subsidence rate in the plane, the basin can be divided into three zones from east to west and several belts in the same zone from north to south for each period. The variant change of subsidence evolution is related to the phase of basin evolution and structural characteristics. The holistic subsidence of the whole basin is controlled by basin dynamics, and the temporal-spatial variation of subsidence is affected by both basin dynamics and structural framework.

“…Correlation between sedimentary facies and palebathymetry in the PRMB (modified after L. Chen et al, ; M. He et al, )…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cenozoic subsidence history of the Pearl River Mouth Basin, northern South China Sea

Liu

et al. 2019

“…The SCS is the largest and deepest marginal sea in the western Pacific Ocean. The PRMB, Qiongdongnan Basin, Yinggehai Basin, Beibuwan Basin, and Taixinan Basin located on the northern continental margin of the SCS are Cenozoic sedimentary basins upon Mesozoic basement consisting of granites, sedimentary rocks, and metamorphic rocks (An et al, ; Cheng et al, ; Li et al, ; Sun, Wu, Cartwright, & Dong, ; Zang et al, ; Hui et al, ; He et al, ; Figure ). The PRMB is a NE–SW‐trending sedimentary basin located in the centre of the northern SCS margin and covers about 175,000 km 2 (Figure ).…”

Section: Geological Frameworkmentioning

confidence: 99%

“…The Xijiang Sag is a large offshore oil‐bearing Cenozoic sedimentary basin in the north‐west part of the PRMB (Ding et al, ; Huang, Peng, & Liu, ). The study area has undergone multiple rifting phases during the Palaeocene to the early Oligocene (He et al, ; Tang et al, ), which are associated with the rifting processes in the Chinese south‐east continental margin (Franke et al, ; Zhong et al, ; Zhu, Li, Sun, & Li, ). The rift stage of the PRMB can be divided into two phases of successive extension with different directions (Cullen, Reemst, Henstra, Gozzard, & Ray, ; Hu et al, ; Li et al, ; Li, Lei, Zheng, Duan, & Yan, ; Li & Rao, ; Ru, ; Wu, Hu, & Zhong, ; Zhou et al, ; Zhu et al, ), which resulted in the Wenchang and Enping formations.…”

Section: Introductionmentioning

confidence: 99%

“…phases during the Palaeocene to the early Oligocene (He et al, 2017;Tang et al, 2017), which are associated with the rifting processes in the Chinese south-east continental margin (Franke et al, 2014;Zhong et al, 2014;Zhu, Li, Sun, & Li, 2016). The rift stage of the PRMB can be divided into two phases of successive extension with different directions (Cullen, Reemst, Henstra, Gozzard, & Ray, 2010;Hu et al, 2016;Li et al, 2014;Li, Lei, Zheng, Duan, & Yan, 2015;Li & Rao, 1994;Ru, 1988;Wu, Hu, & Zhong, 2015;Zhou et al, 1995;Zhu et al, 2015), which resulted in the Wenchang and Enping formations.…”

mentioning

confidence: 99%

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Fault interaction and evolution during two‐phase rifting in the Xijiang Sag, Pearl River Mouth Basin, northern South China Sea

Chen

et al. 2019

Fault geometries, various fault interactions, and fault evolution during the Palaeogene two‐phase rifting in the north‐west Xijiang Sag, Pearl River Mouth Basin, are examined using 2D and 3D seismic data. The study area is characterised as a half‐graben bounded by a NE‐striking SE‐dipping listric fault, and it has been proven to have undergone two phases of extension during the Palaeogene rifting stage. The study area comprises several fault sets with different strikes, mainly including NE‐striking and E‐W‐striking faults. Various styles of fault interactions have been examined in this study, which vary in different regions. Based on observations made in this study, we suggest that (1) major E‐W‐striking faults may either abut against or cross‐cut the boundary fault; (2) many thin‐skinned E‐W‐striking faults mainly develop in groups in the unruptured sub‐sag; and (3) most NE‐striking faults are continuously active in Rift Phase 2 on the slope. The NE‐striking faults initiated in Rift Phase 1, while most of the E–W‐striking faults formed in Rift Phase 2. Our results demonstrate that the major E‐W‐striking faults are prone to cross‐cutting the boundary fault surface during Rift Phase 2, which results in the transformation of two‐phase basin architectures. Compared to previous physical model results, we suggest that our natural fault characteristics support the model's conclusions and that the angle between the first‐ and second‐phase extension directions is an important factor that influences the styles of fault interaction and fault evolution during a two‐phase extension.

Structural characteristics and development model of fluid diapirs within the structural transition zone, northern South China Sea

Qin,

Liu,

Peng

et al. 2024

Self Cite

Fluid diapirs are widespread in the northern South China Sea (SCS), are significant indicators of the existence and distribution of hydrocarbons and natural gas hydrates and are of great petroleum geological significance. Based on high‐precision 3D seismic and drilling data, this paper analyses the tectonic features and genetic mechanism of a fluid diapir zone in the northern SCS and a development model of fluid diapirs is proposed herein. Studies have revealed that the northern SCS large‐scale fluid diapir zone is located within a concealed structural transition zone, which is consistent with the spatial distribution location and direction of a concealed structural transition zone and that the formation of a fluid diapir zone is strongly influenced by the structural transition zone. Fluid diapirs are large continuously spreading bright reflection zones in shallow surface layers and are downwards converging high‐variance ribbons in middle and shallow layers, all of which are spreading in a NW–NNW orientation on the plane. The profile shows a conical or mushroom‐shaped shape that converges from shallow to deep, with a height of approximately 7 km and is characterized by a compound gas chimney fuzzy zone. The main body of the concealed structural transition zone is a slope structure and is flanked by large‐scale NW–NNW‐oriented fault systems. Minor en echelon spreading NW–NNW‐oriented faults and fractures are developed within the structural transition zone and are soft linkages that match well with the distribution direction and location of the fluid diapirs. On the profile, the overall display is a composite flower‐like structure dispersed from deep to shallow, which belongs to a large strike‐slip fault zone with a tectonic transformation effect. A comprehensive analysis suggests that the formation and development of the structural transition zone are mainly controlled by pre‐existing structures in the basement and that minor faults, fractures and slope zones within the structural transition zone serve as dominant pathways for the migration of deep overpressure fluids and gas hydrates. Consequently, the concealed structural transition zone provides favourable conditions for fluid diapirs to develop. Moreover, the stratigraphic overpressure systems mainly caused by gas generation provided the main driving force for the formation of fluid diapirs. Obviously, the development location, distribution direction, formation and evolution of the northern SCS fluid diapirs are jointly controlled by internal minor faults and fractures of the Eocene‐Miocene structural transition zone and the overpressure of the rifting period after the Pliocene. The main development period of the northern SCS large‐scale fluid diapirs was the second phase of the Dongsha Movement. During the exploration of gas hydrates and hydrocarbons in the Pearl River Mouth Basin, it is essential to consider the mutually restricting relationships between fluid diapir structures and gas hydrates and hydrocarbons.