Fig. 1

Structures of the Central Alps, modified after Steck (2008), Steck et al. (2013), Tektonische Karte der Schweiz (2005) and Cavargna-Sani et al. (2014). The Monte Rosa nappe is situated at the western border of the Lepontine tectonic half-window. CL Centovalli line, MFL Malenco-Forno-Lizun nappe, RKG Rote Kuh-Gampel fault, 2DK Seconda zona diorite-kinzigitica, ZH Zone Houillère; (1) Monte Leone basement, (2) Mesozoic and Paleogene sedimentary cover of the Monte Leone, Campo Tencia, Adula and other lower Penninic nappes, (3) Pizzo del Vallone nappe, (9) Brusson window, (10) Canavese Permian-Liassic sediments, (11) Scaredi unit (amphibolite facies grade Ivrea basement), (12) Chiavenna ophiolites, (13) Salarioli Carboniferous-Triassic sediments, (14) Tuftgrat Mesozoic cover of Stockhorn basement, (15) Teggiolo Mesozoic-Paleogene cover of Antigorio nappe, (16) Mesozoic cover of Portjengrat unit, (17) Cristallina Mesozoic cover of Sambuco basement, (18) Bosco unit, (19) Mesozoic-Paleogene Briançonnais cover, (20) Stalden-Berisal-Ruginenta basement, (29) Geisspfad peridotite, (30) Cima d'Agaro peridotite, (31) Moncucco peridotite, (32) Albogno peridotite, (33) Finero peridotite. Note on the Simano nappe: Recent work by the authors has demonstrated West of the Ticino river the subdivision of the classical Simano nappe into two tectonic units of different origin, called Verzasca and Campo Tencia. The prolongation of this separation East of the Ticino is still uncertain and for this reason we provisionally maintain the name Simano