In western Switzerland, the Upper Penninic subdomain contains mainly magmatic and sedimentary rock units of oceanic origin. Some thin continental margin sedimentary series and small continental crust slices are intercalated within these units. All of these units were driven into a subduction zone under the Salassic nappes, some exposed to high-pressure metamorphic conditions, others remaining under lower pressure conditions.

The Upper Penninic subdomain of eastern Switzerland (Graubünden) is represented by oceanic rock associations: mostly sedimentary in the case of the Avers Nappe, largely magmatic in the Platta and Malenco-Forno-Lizun nappes and mainly with the character of a mélange zone for the Arosa Zone.