Growth and linkage of a complex oblique-slip fault zone in the Pearl River Mouth Basin, northern South China Sea

Abstract Oblique-slip faults are ubiquitous in sedimentary basins, but have been largely neglected relative to their dip-slip counterparts. Case studies of oblique-slip faults are very limited. In this study, we used 3D seismic data, tied to well control, to investigate the geometry, kinematic characteristics, growth and linkage, and tempo-spatial evolution of a complex oblique-slip growth fault zone in the Pearl River Mouth Basin (PRMB) of the northern continental margin, South China Sea (SCS). The E-W-oriented 30.5-km-long fault zone consists of two superimposed oblique-slip fault systems. The lower fault system is an integrated zig-zag fault consisting of three ENE-WSW- to E-W-striking, right-stepping, sinistral en-echelon fault segments, which were hard-linked by two NW-SE-trending fault segments; while the upper fault system is composed of nine WNW-ESE-striking, left-stepping, dextral en-echelon component faults, which had overlapping fault tips and were partly hard-linked by breaching of the relay zones. The lower and upper fault systems were activated in the Eocene and the Oligocene to Pliocene, which respectively correspond to the syn-rift and post-rift stages in the PRMB. The fault throws (up to 288 m) and activity rates (up to 34.5 m/Ma) of the upper fault system are overall much less than those of its lower counterpart. Reactivation of the lower syn-rift fault system shows clear influence on the development of post-rift en-echelon fault segments. A four-stage evolution model of the oblique-slip fault zone was presented.