Structural Difference and Control Mechanism of Early Cenozoic Depression in Yangjiang East Sag, Pearl River Mouth Basin

In order to explore the structural difference and control mechanism of Yangjiang east sag in Zhusan depression, the development characteristics of main faults in the sag are finely explained and their activity is analyzed by using three-dimensional seismic data, the distribution characteristics of magmatic diapir are identified and summarized, and the structural differences of different depressions in Yangjiang east sag in Early Cenozoic are systematically studied. The study shows that the special structural position of Yangjiang east sag influences the formation of the sag, and the structural transformation zone controls the differential development of each sag in the study area. Yangjiang No.24 depression in the west is a simple half graben structure with north fault and south overlap, while Enping No.19, No.20 and No.21 depressions in the middle and east is a compound half graben structure with north-south double faults. The deformation of lithospheric crust in the initial stage of rifting is different due to the different extension modes of subsag under the regional stress field. During the same rifting stage, the magma migrated to the lower pressure transition zone and accumulated to form magma chamber. The deep faults in the basement communicated with the deep crust and controlled the magma upwelling and emplacement. The thermal action of magma makes the crustal brittle deformation change into ductile deformation, so the sag near the Yangjiang-Yitong’ansha blind fault zone develops oblique slip fault and presents a compound half graben structure. The above analysis provides a theoretical basis for the prediction and exploration of source rocks in the study area. © 2024 China University of Geosciences. All rights reserved.