The geological basement is made up of purplish phyllites of the Upper Salmian (Cambrian). This group of fagnes has a very large diversity of plant groups: floating peat bogs with narthecium (Narthecium ossifragum) and filiform grass (Carex lasiocarpa), peat bogs with sphagnum cottongrass (Eriophorum vaginatum), bog acid with cloverleaf water (Menyanthes trifoliata) and comaret (Comarum palustre), dry heaths with nard (Nardus stricta) and arnica (Arnica montana), wet heaths with ericaceous, etc.