strati.ch - Lithostratigraphic Lexicon of Switzerland

Representation and status

Historical Variants: Ophiolithzug Val Maroz-Malenco (Staub 1921), Zone von Châtillon-Malenco (Staub 1942b), Malenker Ophiolith-Decken (Staub 1946), Zone Disgrazia-Val Malenco (Roesli 1946), Forno-Decke, Monte-del-Forno-Serie (Ferrario & Montrasio 1976), Monte-del-Forno-Komplex (Peretti 1985), Falda ofiolitica Malenco-Forno (Sciesa 1991), Malenco-Forno-Lizun-Einheit (Spillmann 1993), Malenco-Forno-Lizun units (Manatschal 1995), Malenco-Forno-Lizun-Decke (Spillmann & Trommsdorff 2007), Malenco-Forno-Lizun Nappe (TK500 / Gouffon et al. 2024), cf. Trommsdorff et al. 1993

Description: Reliktischer exhumierter subkontinentaler Mantel, ozeanischer Basalt und Sedimente.

Tectonic unit (resp. main category)

Kind of protolith

Definition: Staub R. (1921) : Geologische Karte der Val Bregaglia (Bergell ; 1:50'000). Geologische Spezialkarte 90

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

p.78: Three units with distinct lithological assemblages of oceanic origin, situated in adjacent areas, form the Malenco-Forno-Lizun Nappe. The Malenco unit (Montrasio et al. 2005) consists of large volumes of serpentinite that represent exhumed subcontinental mantle formerly exposed at the ocean floor, and, in a small area adjacent to the Margna Nappe, a transition into continental lower crust in Permian granulite facies, associated with a Permian gabbroic intrusion (Müntener & Hermann 1996). Further north, the Forno unit consists of metabasalts and metagabbros of oceanic origin covered by metasedimentary rocks of Jurassic to Early Cretaceous age, which are in direct contact with the roof of the Bregaglia Intrusion (Puschnig 1998, Froitzheim et al. 1996 a). The Lizun unit, located around the Piz Lizun, northwest of the Engadine Fault and sinistrally offset from the Forno unit (Schmid & Froitzheim 1993), exposes same rocks of oceanic origin as in this latter unit (Liniger & Nievergelt 1990). The Malenco-Forno-Lizun Nappe, together with the Platta Nappe, is located in the hangingwall of the Turba Normal Fault (Nievergelt et al. 1996).

Important Publications: Trommsdorff V., Piccardo G. B., Montrasio A. (1993) : From magmatism through metamorphism to sea floor emplacement of subcontinental Adria lithosphere during pre-Alpine rifting (Malenco, Italy). Schweiz. mineral. petrogr. Mitt. 73, 191-203