The Roisan-Cignana Shear Zone consists of slices of Mesozoic sediments and crystalline basement in a mylonitic matrix derived from the adjacent Dent Blanche Nappe (Arolla Unit) and of the Mont Mary Nappe (Lower and Upper units). The high-pressure mineral assemblages along the contact between these tectonic slices indicates that their emplacement occurred in an early deformation stage, before or during the subduction.

Microquartzites rubanés à niveaux manganésifères, ferrugineux et phosphatés, présents localement dans la zone de Roisan.

Marbres, marbres dolomitiques, dolomies fines et sombres, dolomies blanchâtres plus grossières et litées, fins niveaux de quartzites, brèches.