Falda del Monte Leone

Representation and status

Historical Variants: nappe III = nappe du Monte Leone (Argand 1911), Monte Leonedecke (Bosshard 1925), Monte Leone-Ofenhornteildecke (Grütter 1929), Monte-Leone-Decke = Decke III (Bader 1934), M. Leone-Gneissmasse = Monte Leone-Zone (Wieland 1966), falda del Monte Leone (Dal Piaz et al. 1992a), nappe du Monte Leone (Jeanbourquin & Burri 1989, Carrupt & Schlup 1998), nappe n°3 = Monte Leone nappe (Carrupt 2003), Monte Leone nappe (Steck et al. 2013), Falda di ricoprimento del Monte Leone (Della Torre & Maggini 2015), Monte Leone Nappe (Berger et al. 2017, Gouffon et al. 2024)

Description: Falda del Lepontico occidentale, con basamento paleozoico ortogneissico (caratterizzato da una grande variazione di litotipi) e copertura autoctona mesozoica, ben sviluppato nella parte frontale (Serie del Holzerspitz).

Subordinate units

Age at top

Note about top

sicher bis Jura, ev. noch bis Paläogen

Age at base

Geographical extent: Lepontinische Alpen: Simplon-Tessin-Dom bis südöstlich von Visp (Gantertal) [kommt auf den GA25-Blättern 034_Basodino, 061_Simplon, 093_Brig, 145_Bosco/Gurin, 153_Raron, sowie XXX_Binntal und XXX_Helsenhorn vor].

Type locality

Paleogeography

Valaisan Basin

Tectonic unit (resp. main category)

Definition: Argand Emile (1911) : Les nappes de recouvrement des Alpes Pennines et leurs prolongements structuraux. Mat. Carte géol. Suisse (N.F.) 31/1, 30 pages

Definition: Gouffon Yves (Editor) (2024) : Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern

p.48: The Monte Leone Nappe is the highest of the Lepontic units in the Toce Culmination. It is involved in the large synformal Berisal Backfold and further east, after following the Rhône-Simplon Fault, in the Alpe Bosa-Wandfluhhorn double fold (e.g., Steck et al. 2001). This nappe consists mainly of a crystalline basement made of various orthogneisses (Ordovician and Permo-Carboniferous) and paragneisses, covered by a relatively reduced Triassic–Cretaceous(–Paleogene?) sedimentary series. A particularity of this nappe is the presence of a large ultramafic body (Geisspfad) within the gneisses.