AGE AND SETTING OF THE CENOZOIC VOLCANISM IN THE TEFIDET GRABEN (RIFTSYSTEM OF EASTERN NIGER)

In the Oligocene to the Pliocene-Pleistocene, an important volcanism o ccurred in the Tefidet Graben, which belongs to the Early Cretaceous T enerean Rift System (Niger). Nephelinitic lavals are located along nor th-south fractures related to major structural lineaments of the crust al basement. Basanitic lavas have been erupted from N 115-degrees-150- degrees trending fractures parallel to the normal faults of the Cretac eous Graben. Once can note a synchronous initiation of a new volcanic activity in the West Africa around 35 Ma, which could be explained by a reorientation of the stress field.