The Fault Assembly Characteristics on the Northern South China Sea Continental Margin and its Implications on the South China Sea Spreading

Being the largest marginal sea on the southeastern continental margin, the South China Sea is controlled by the subduction and convergence of the Pacific, Eurasian and Indo-Australian plates, and has a complex formation mechanism and evolutionary history. At the beginning of the Cretaceous, a series of NE-NEE-trending extensional shear lithospheric faults developed in the south and north of the South China Sea Basin. During the Oligocene, most of the faults inherited the old fault activities. Ever since the late Miocene, the Philippine Sea Plate continued to subduct westward, and a large number of near-EW-NEE-trending extensional normal faults and NWW-NW-trending shear basement faults occurred in the northern continental margin of the South China Sea. Intersecting of the two-phase faults represents the interaction between plates at different times. However, issues concerning the vertical tectonic activities, factors controlling the distribution of sediments, and their relationships with the movement of the surrounding plates remain elusive. Most importantly, the formation process of these fault systems and the opening mode of the South China Sea basin are issues worthy of deep digging. Aiming at the NE and EW trending fault systems in the continental margin of the northern South China Sea, this paper selects the Pearl River Mouth Basin where the NEE- and NW- trending fault systems are most developed, and uses the gravity and magnetic anomalies, sedimentary strata and seismic reflection profiles to systematically analyze the structural characteristics and activity history of the faults. The results show that a series of NEE-trending fault zones (such as the Littoral Fault Zone) in the northern continental margin of the South China Sea are likely to be the main faults controlling depressions in the Pearl River Mouth Basin, and the faults www.d experienced the early low-angle detachment, and the second phase high angle normal fault and the right-lateral strike-slip since the third Oligocene period. They correspond to three tectonic stages: rifting stage, post-rifting depression stage and fault block activity, reflecting the subduction and convergence rates of the plates around the South China Sea Basin, which demonstrates that this group of faults played an important role in the opening of the South China Sea during the change of subduction direction. © 2022 Science Press. All rights reserved.