The Lagoons’ Fault impact on the genesis of bituminous sandstones of south-east of the Ivory Coast: Lithological and environmental aspect

The trace of the Lagoons’ Fault permitted to understand the distribution of bitumen in the onshore sedimentary basin in South-east of Ivory Coast. The bituminous formations met are made up mainly of bituminous sandstone which are sometimes associated with other bituminous formations (microconglomerats, sands, kaolins, glaucony, marly limestones and fossiliferous rocks). The bituminous sandstones are quartz wackes resulting from the consolidation of old quartzose sands by the bitumen. There are nano-vacuums between the grains quartz and the bitumen of these sandstones. This bitumen comes from the hydrocarbons which were formed in South of the Lagoons’ Fault in the surroundings of Eboinda. They were spread by diffusion through paleo-beaches and communicating paleo-channels before reaching the layout of the Lagoons’ Fault and its satellite faults. It is thanks to these faults and to other communicating paleo-channels that the bitumen could migrate to North of the Lagoons’ Fault between Samo and Grand-Bassam even beyond on a distance of at least 75 km. The bitumen is trapped in the form of lenses in fluviatile paleo-channels and paleo-beaches located between Eboinda and Grand-Bassam. The migration was done from East to West. The bituminous sandstones are in outcrop, subsurfaces and in the sublagoonals; that involves a contamination of soils, phreatic water table and lagoons surrounding.