In Western Switzerland, the internal part of the Lower Penninic subdomain is only represented by the Sion-Courmayeur Nappe, which extends along the entire front of the Penninic domain. Paleogeographically it corresponds to the oceanic Valaisan Basin, which was then incorporated in the subduction zone below the Middle Penninic units.

In Eastern Switzerland, the internal part of the Lower Penninic subdomain is represented by metasedimentary, mostly shaly-calcareous units (so called “Bündnerschiefer”, incl. in the Prättigau Half-Window and the core of the Lower Engadine Window), deposited in the oceanic Valaisan Basin. Ophiolitic remnants are found at the base of some of the “Bündnerschiefer-type” nappes.