The Châtillon-St-Vincent Slices are Upper Penninic tectonic units situated between the Zermatt-Saas Fee Nappe and the Tsaté Nappe. They comprise eclogitic continental basement rocks similar to that of the structurally higher Dent Blanche and Sesia nappes. They are likely derived from extensional allochthons, formed during the Jurassic opening of the Piemonte-Liguria Ocean in a more distal position than the Cervinia Terrane from which the Salassic nappes originate.