Evolution of the boundary fault system and its influence on basin structure in the Baiyun Sag, Pearl River Mouth Basin

The Pearl River Mouth Basin has experienced multi-stage tectonic activity and developed complex fault systems since the Cenozoic. Limited by the available time-domain seismic data, previous studies have focused on the overall structure and evolution of the basin and much is still unknown about the boundary faults. We analysed the boundary fault system of the Baiyun Sag using 3D depth-migrated seismic reflection data, which provided new insights into the basin structure and migration of the depocentre. Several large boundary faults pass through the Tg basement in the Baiyun Sag. The activity of these faults has been affected by the rotation of the stress field in the region of extension and by magmatism in the basin. There are differences in the structure of the Baiyun Sag from west to east. The western basin is controlled by steeply dipping faults, whereas the eastern basin is controlled by wide, gentle, low-angle faults, resulting in a detachment basin. The four stages of basin evolution can be divided into: (1) an initial synrift stage; (2) a strong synrift stage; (3) a transition stage; and (4) a post-rift stage. The Baiyun Sag has been affected by changes in the intensity of fault activity and the depocentre has gradually migrated from south to north.