Neogene

Tectonics

Subduction

Fault (geology)

Seismology

Passive margin

Geology

Paleontology

Structural basin

Continental margin

Rift

Eurasian Plate

Cenozoic

Earth-Science Reviews

The East Asian continental margin straddles the boundary between the Pacific Subduction Domain to the east and the Tethyan Collision Domain to the west. The spatial and temporal interaction between these two dynamic domains induced a dextral trans-tensional stress field, generating nearly 75% of the globe's marginal seas and continental margin rifts during the Cenozoic. Among these, the South China Sea (SCS) and its northern margin are located in the core of the Pacific Subduction Domain and the Tethyan Collision Domain. The evolution of the SCS and its northern margin are of prime interest because of their spectacular magnetic lineations and strong rifting. In spite of the several investigations carried out on the Cenozoic marginal seas and rift basins, their formation mechanisms remain equivocal. Here we perform a comprehensive analysis of seismic profiles and fault architecture data with a view to understand the Cenozoic tectonic evolution of the northern margin of the SCS. Based on detailed structural analysis of the geometry and kinematics, we demonstrate that the NE- and ENE-striking faults assembled to horsetail- or feather-shaped structures in plan view, which display flower-like structures in seismic profiles. Two stages of faulting along NE-trending faults are identified along the northern margin of the SCS. The earlier oblique extension occurred during the Paleocene to the early Middle Eocene (~44–42 Ma), accompanied by strong rifting and formation of some left-step en echelon-like faults. The later trans-tensional faulting developed during the late Middle Eocene to the Early Miocene (~21 Ma), resulting in the formation of the dextral right-step trans-tensional fault system. Two stages of faulting were linked to the joint effect among the Indo-Eurasian collision to the west, the subduction of the Pacific Plate to the east and the slab pull of the proto-SCS to the south. Our study provides important insights into the dynamics and tectonics controlling the opening of the South China Sea. During the Late Eocene to the Oligocene, the dextral trans-extensional faulting along the right-step strike-slip fault system caused the opening of the Northwest Sub-basin, the East Sub-basin and the Northeast Sub-basin. However, during the Early Miocene, the sinistral strike slipping of the Ailao Shan-Red River (ASRR) shear zone and the slab-pull force of the proto-SCS resulted in the opening of the Southwest Sub-basin and the change of the spreading direction of the East Sub-basin.

Structural and kinematic analysis of Cenozoic rift basins in South China Sea: A synthesis