Along-Strike Variation and Genetic Controls of the Yangjiang–Yitong Fault Zone in the Pearl River Mouth Basin, Northern South China Sea

The along-strike segmentation and evolutionary mechanisms of the Yangjiang–Yitong Fault Zone (YYFZ), a major basement-involved fault zone in the Pearl River Mouth Basin (PRMB), remain poorly constrained. We integrate high-resolution 3D seismic, borehole, and core data to investigate the geometric and kinematic differences between the northern and southern segments and their controls on sag development and magmatism. The results show that the Panyu Low Uplift separates the YYFZ into two transtensional segments. The southern segment comprises a large-scale, right-stepping en echelon fault system that acted as a major strike-slip transfer zone and promoted sag development, whereas the northern segment is characterized by small-scale, left-stepping faults that primarily limited depocenter development. The spatial and temporal coupling between fault activity and magmatism indicates northward, stepwise propagation and linkage of the fault system during the post-rift stage. We propose an evolutionary model in which inherited basement heterogeneity, successive changes in the regional stress regime, and differential reactivation jointly controlled the segmented structural architecture of the YYFZ. In the south, concentrated, high-strain shear zones were reactivated earlier and more strongly, promoting sag formation. By contrast, deformation in the north was more diffuse, and reactivation occurred later and was weaker, limiting depocenter development. This model highlights the role of basement heterogeneity in controlling fault segmentation and differential rift evolution along passive continental margins.