The Moncucco Nappe (Western Lepontic) occupies the core of the Vanzone Antiform in the Valle d’Ossola. It consists of a crystalline basement intruded by a Permian granite and is interpreted as the equivalent of the Monte Leone Nappe in the hangingwall of the Simplon Fault. Similar to that nappe, the Moncucco Nappe contains a large ultramafic body at its top.