Phénomènes karstiques en milieux non carbonatés. Etudes de cavités et problématique de leur développement au Niger Occidental

The study of several caves in siliceous formations belonging to the Precambrian basement and its Cenozoic sedimentary cover brings to the fore the importante of an underground drainage network in relation with crustal fracturation. This network guides the waler transfer from the land surface to the depth and generates géomorphologic phenomena similar to those in calcareous areas. The study of caves in a siliceous environmemts shows the importance of solution phenomena in their formation and also in that of West Niger landscapes. Therfore, a general model of topographic evolution îs proposed.