The Middle Penninic subdomain comprises tectonic units located between the Lower Penninic subduction surface and the major thrust of the Upper Penninic. Paleogeographically, these units are derived from the Briançonnais Terrane. They are formed of a polycyclic crystalline basement, cut by Late Cambrian (ca. 500 Ma) and Permian (ca. 270 Ma) granitic intrusions, by Permo-Carboniferous sediments that filled narrow basins and a characteristic Mesozoic – Paleogene sedimentary cover (much of it detached at the level of the Triassic evaporites to form some of the nappes in the Prealps).