Structural Characteristics and Formation Mechanism of the Strike-Slip Fault System in Eastern Doseo Basin, Chad

Doseo Basin is an important petroliferous basin in Africa. Its formation and evolution are controlled by the long-term activities of Central African shear zone, which have played a significant role in oil and gas accumulation. Based on the latest 2D and 3D seismic data and drilling data, this study systematically describes the structural styles and distribution characteristics of the strike-slip fault system in the eastern Doseo Basin and analyzes the structural characteristics of typical strike-slip faults. Combined with the regional tectonic setting, the evolution stage and formation mechanism of the strike-slip fault system are further investigated. The results show that: (1) The strike-slip fault zone in the eastern Doseo Basin has developed multiple profile structural styles, such as negative flower structure and compound flower structure, and various planar structural styles, such as linear structure, en echelon structure, braided structure, horsetail structure, etc. What’s more, “Dolphin effect”, a unique spatial characteristic of strike-slip faults, has also been recognized in the study area. (2) Two of the planar structural combinations in the strike-slip fault zones have been identified in this study, which are en-echelon-overlapping-horsetail combination and linear-horsetail combination. The main strike-slip faults and branch faults show typical dextral strike-slip fault characteristics. (3) The strike-slip fault system in the eastern Doseo Basin is mainly shaped by 5 tectonic evolution stages. During Berriasian-Barremian in the Early Cretaceous, half graben structure was developed by NNW-SSE extensional stress; The NEE-SWW extensional stress of Aptian-Albian led to the formation of various transtensional structures, such as negative flower structure; During Cenomanian-Coniacian in the late Cretaceous, the basin experienced thermal subsidence; Santonian was characterized by near N-S compressional stress, which formed anticline/faulted anticline in the center of the “flower”; Faulted nose structure was further developed on the edge of the “flower” by NW-SE compressional stress during Eocene. They were arranged in rows in NE-SW direction, and provided good trap conditions for oil and gas accumulation.