Structural Evolution and Sedimentary Response of a Detachment Convergent Transfer Zone in the Central Part of the Pearl River Mouth Basin, Northern South China Sea Rifted Margin

Abstract The western Baiyun area in the northern South China Sea, particularly within the center Pearl River Mouth Basin (Zhu‐2 Depression), hosts a detachment system with a single south‐dipping detachment fault and multiple north‐dipping counterparts. This study investigates the structural evolution and sedimentary responses of a detachment convergent transfer zone in this region. Integration of Eocene borehole data with recent high‐resolution 3D seismic data reveals that magmatic activity and pre‐existing fault systems controlled basin subsidence during the rifting phase (56–39 Ma). Early development of the convergent transfer zone was influenced by reactivation of pre‐existing basement faults, which generated high‐angle normal faults that accommodated brittle upper‐crustal extension. From ∼43 Ma (late Wenchang stage), the deformation style shifted to lower‐crustal ductile thinning, forming ductile‐crust domes and east‒west‐aligned rotated fault blocks. This phase also saw the rotation of earlier high‐angle normal faults into low‐angle detachment faults, culminating in the formation of the detachment convergent transfer zone. This structural reorganization amalgamated previously isolated, narrow, and deep lacustrine basins into a unified, wide, and shallow basin. Concurrently, the sedimentary system evolved from fan delta‐braided river delta assemblages to braided river delta‐beach bar systems. Constraining the spatiotemporal distribution of dynamic uplifts and associated beach‐bar deposits within this structural zone provides critical insights for predicting potential reservoirs in deep‐water continental margins.