Gravity‐Driven Collapse of Continental Crust in the Northern South China Sea Margin

Gravity‐driven tectonics is a fundamental process in Earth's geological evolution; however, its role and governing mechanisms during syn‐extensional deformation at the crustal scale along passive continental margins remain poorly constrained. In this study, we use high‐resolution seismic reflection data to investigate coupled brittle and ductile deformation in the Xingning sub‐basin of the northern South China Sea. Our analysis documents deformation of the supradetachment basin, the Xingning detachment fault, and associated ductile deformations in the footwall. Key observations include: (1) the supradetachment basin comprises late Eocene syn‐rift strata that wedge toward the bounding detachment fault; (2) the NW‐striking Xingning detachment fault extends for ~90 km along strike and shows marked along‐strike variations in geometry, characterized by a ramp‐flat‐ramp segment in the southern and northern domains and a listric geometry in the central domain; (3) three footwall domes developed from 40 to 23 Ma; and (4) recumbent folds within the ductile crust beneath the Xingning detachment fault show two distinct hinge orientations, including NW‐trending hinges parallel to regional extension and NE‐trending hinges aligned with the slip direction of the Xingning detachment fault. The syn‐kinematic coupling between detachment faulting and ductile flow is interpreted to reflect gravity‐driven collapse along the flank of an elevated ductile dome, thermally weakened by magmatic underplating in the deep crust. These results provide clear evidence for gravity‐driven, syn‐extensional crustal‐scale deformation along a rifted continental margin in the northern South China Sea, highlighting the fundamental role of gravitational processes during continental rifting.