The Zermatt-Saas Fee Nappe is an Upper Penninic tectonic unit of the Western Alps consisting of rocks of Middle to Late Jurassic age derived from the Piemonte-Liguria Ocean. They are mostly large bodies of serpentinites, metagabbros and metabasalts in which pillow structures are locally well preserved. Oceanic sediments overlie these ophiolites, in particular metacherts (metaradiolarites). All of these rocks display relics of Early Eocene high-pressure metamorphism in eclogite facies.