Tectonic Control on Basin-Fill Architecture in a Detachment-Convergent Transfer Zone: The Pearl River Mouth Basin Example

The western Baiyun area in the northern South China Sea, particularly within the central Pearl River Mouth Basin (Zhu‐II Depression), hosts a complex detachment system. This study elucidates the tectonic control of a detachment-convergent transfer zone on the spatiotemporal evolution of the sedimentary basin system during the Eocene rifting. Integration of borehole and high-resolution 3D seismic data reveals that magmatic activity and reactivated pre-existing faults governed initial basin subsidence and the early development of high-angle normal faults in the upper crust. A fundamental shift occurred around ∼43 Ma (late Wenchang stage), when deformation transitioned to lower-crustal ductile thinning. This drove the formation of ductile‐crust domes, the rotation of faults into low-angle detachments, and ultimately, the establishment of the detachment-convergent transfer zone. This structural reorganization directly controlled basin geometry, transforming it from isolated, narrow, and deep lacustrine depocenters into a unified, wide, and shallow basin. Consequently, the sedimentary system evolved from fan delta‐braided river delta assemblages to braided river
delta‐beach bar systems. Constraining this tectonically dictated basin-fill architecture provides critical insights for predicting potential reservoirs in deep-water continental margins.