New data obtained from the study of the Kenyan and Tanzanian coastal basins establish a rifting period at the end of the Karoo sedimentation (Upper Triassic/Lower Jurassic), in the northeastern margin of Gondwanaland. The rifting period was followed by an erosive phase and then transgression of a Tethyan sea during the Middle Jurassic. This leads to a modification of the stratigraphic succession of the region and gives new datas about the nature of separation and drifting of Gondwanaland, the genesis of the proto-Indian ocean and the paleoposition of Madagascar