Consequences of preexisting faults on rifting patterns: Insights from multichannel seismic data of the Shunde rift, Northern South China Sea

Abstract

Preexisting faults as the products of previous tectonic events are common in the passive continental margins. Recent studies have proposed the existence and significance of the preexisting faults in the Northern South China Sea (NSCS). Here, we present newly acquired 3D high-resolution seismic data across the Shunde Rift that allow us to observe a series of preexisting faults within the basement. The results suggest that the Shunde Rift is characterized by the presence of at least two sets of preexisting faults: a NE trending fault set and an E-W trending fault set. Considering the tectonic events that have occurred since the Mesozoic, we propose that the formation of E-W-trending faults can be attributed to the Late Triassic to Early Jurassic collision between Indochina and South China. Subsequently, NE trending faults developed due to northwestward subduction of the paleo-Pacific plate during Mid Jurassic to Late Cretaceous. Some of preexisting faults display reactivity during the early Cenozoic and exert primary control over the geometry and evolution processes of the Shunde Rift. The inherited faults primarily trend in a NE direction, significantly thinning the upper crust and forming a core complex type extension structure. This suggests that the NE trending preexisting faults may play a more important role in Cenozoic rifting of NSCS compared with E-W preexisting faults.