Sedimentary evolution of the passive continental margin of the north sub-basin, Senegel Basin and its controlling factors

The north sub-basin of the Senegel Basin is a rift and passive continental margin superimposed basin along the Atlantic coast of Northwest Africa. It is characterized by multiple types of continental slopes, well-developed carbonate sediments and relatively underdeveloped salt structures. Based on the seismic and drilling data of the southern area of the sub-basin, this paper analyzed the paleogeomorphic evolution of the continental slope and the sedimentary filling history during the development period as a passive continental margin basin. Main controlling factors for the geological characteristics of the sub-basin are discussed in the paper. The study reveals that during Cretaceous, the continental slope of the study area had experienced several phases of evolution, from the platform margin slope, to the syndepositional fault slope, and to the broad and gentle sedimentary slope, corresponding to the tectono-sedimentary evolution stages: the carbonate platform construction stage of early Cretaceous, the Albian-Santonian stages while the clastic deposits area be separated into internal and external areas by fault slope, and the Campanian-Maastrichtian stages dominated by a gentle slope covered by clastic deposits. Sediment distributions in different stages show different depositional patterns. Global sea level changes and relatively insufficient supply of terrigenous clastic are important factors for the sediment filling features of the passive continental margin basin in the study area. Regional tectonic activities have a direct impact over the evolution of landform, the occurrence of unconformity and the movement of provenance back and forth in the study area. The paleoclimate and provenance conditions have indirect influences on the type, scale and sediment depositional pattern in the basin.