Deformation Characteristics And Formation Mechanism Of Mud Shale Diapir Structure In Niger Delta

Niger Delta is located in the western margin of the African continent.It is a sedimentary basin of the Cenozoic delta superimposed on the passive continental marginal rift.Rio Del Rey basin,the secondary basin on its northeastern margin,is part of its territory in Cameroon.The stratigraphic and tectonic features are very consistent with the Niger Delta Basin.According to the lithology,the basin has three formation units: Akata formation,Agbada formation and Benin formation.Mud is the main diabase of the Akata formation.During the process of delta accumulating,Akata Formation and the overlying stratum formed a complex and variable mud structure due to the influence of the sedimentation and the gravity(sliding and spreading)of the continental margin.Based on the three-dimensional seismic area of Rio Del Rey Basin and regional sections of Niger Delta Basin,this paper provides a detailed explanation of representative seismic sections of multiple trans-basins,compiles regional balanced evolution profiles,and analyzes typical tectonic styles.Rio Del Rey basin is divided into the trailing edge extensional zone,the mudstone diapir zone,the leading edge extrusion zone,and the volcanic uplift zone.Then,according to the interpretation of seismic data and the results of balanced profile recovery,different boundary conditions were designed to control experimental variables such as mudstone thickness,slope angle and overlying stratum thickness.It is analyzed that the formation and evolution of the mud diapir structure in Rio Del Rey basin is the result of the interaction of the upper sedimentation,gravity(sliding and expansion),and is influenced by the thickness of the mudstone layer,the thickness of the overlying stratum,the slope and dip of the basement and tectonic stress.