Abstract: The coherence technique can objectively describe the plane distribution of the fault system developed in a special period. This paper introduces how the coherence technique is used to analyze the faulting characteristics within the 3D study area at the south margin of the Baiyun sag, the Pearl River Mouth Basin, in order to further understand the structural features of the Baiyun sag. The analysis results indicate that the Lower Oligocene Enping Formation top (T₇⁰) is a regional unconformity, below which NE faulting activity was dominant and stopped in the Early Oligocene, and above which NW fault activity was dominant and kept active from the Eocene to the Miocene. The faulting stage of the Baiyun sag ended in the early Oligocene, and then the depression characteristics was kept for a long term. The faulting and structural evolution within the study area reveals that the Lower Oligocene Enping Formation top (T₇⁰) is the fault-depression transition interface in the Baiyun sag, which is significant for sedimentary evolution and hydrocarbon accumulation within the deepwater area in the sag.

Key words: faulting characteristics, coherence analysis, the south margin of the Baiyun sag, fault-depression transition