1. Interactions between pre-existing structures and rift faults: Implications for basin geometry in the northern South China Sea.
- Author
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Wei Guan, Lei Huang, Chiyang Liu, Guangrong Peng, Han Li, Chao Liang, Lili Zhang, Hongbo Li, Zhe Wu, Xin Li, and Ruining Hu
- Subjects
SHEAR zones ,MESOZOIC Era ,CONTINENTAL margins ,OROGENIC belts ,SUBDUCTION ,CENOZOIC Era ,GEOMETRY ,THRUST faults (Geology) - Abstract
The northern South China Sea (SCS) margin evolved from the Mesozoic convergent to Cenozoic divergent continental margin, and thus, it developed on a heterogeneous crystalline basement with inherited Mesozoic structures. Pre-existing structures and their interactions with rift faults have historically not been described or interpreted in the intensely stretched Baiyun sub-basin. Large-scale 3D seismic reflection data allow us to identify four types of Mesozoic tectonic fabrics within the basement and explain their genesis: (1) Thin, isolated and north-dipping seismic reflections 1, interpreted as thrust faults representing orogenic processes. Tilted thick seismic reflections 2 are formed by reactivation of seismic reflections 1 during post-orogenic extension, which are all related to the NW-ward subduction of the palaeo-Pacific plate. (2) Thin, isolated and shallowly dipping seismic reflections 3 and low-amplitude, semi-transparent and chaotic seismic reflections 4 represent the low-angle thrust system and the associated nappe units, which are related to the shift from NW-to NNW-ward subduction of the paleo-Pacific plate. Subsequently, we investigate the structural interaction between Mesozoic intra-basement and Cenozoic rift structures. Syn-rift, post-rift and long-term faults are developed in Cenozoic strata, and quantitative statistical and qualitative analyses revealed two main types of structural interactions between them and underlying intra-basement structures: (1) Rift faults develop with inheritance of intra-basement structures, including fully and partially inherited faults. (2) Rift faults modify intra-basement structures, although they are controlled by intra-basement structures at an earlier stage. Finally, our results reveal the control of pre-existing structures on the geometry of the Baiyun sub-basin, especially the selective reactivation of NE-trending shear zones (SR2), which are influenced by the regional stress field and the width and dip of the shear zones. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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