strati.ch - Lexique lithostratigraphique de la Suisse

Représentation et statut

Variantes historiques: Monometamorphic Cover Complex (Pognante et al. 1987, Venturini et al. 1994), Bonze unit = Bonze metasediments (Babist et al. 2006)

Termes génériques

Type de protolithe

Métamorphisme: monocyclique-polyphasé
Remarque sur le métamorphisme: polyphase Alpine metamorphism (Babist et al. 2006)

Définition: Babist J., Handy M. R., Konrad-Schmolke M., Hammerschmidt K. (2006) : Precollisional, multistage exhumation of subducted continental crust: The Sesia Zone, western Alps. Tectonics 25

A thin, discontinuous strand of highly deformed Mesozoic metasediments and subordinate metabasite, the Bonze unit in Figure 2, separates the Bard and Mombarone nappes along most of their mutual contact. These sediments are very similar to Late Paleozoic to Jurassic sediments of the Canavese Zone exposed along the contact of the Mombarone nappe with the Ivrea Zone. The latter sediments represent the distal part of the Adriatic passive continental margin [e.g., Biino and Compagnoni, 1989; Ferrando et al., 2004]. Likewise, the Bonze unit contains lithologies (volcanoclastics, dolomitic marbles, manganiferous quartzites and calc-silicate schists; part of the GM subunit of Pognante et al. [1987] and Venturini et al. [1994, 1996]) that are diagnostic of a distal passive margin or a transitional continent-ocean setting, as discussed below). As described in section 3, both the Bonze and Canavese metasediments experienced greenschist-facies overprinting, in some places preceded by Alpine blueschist-facies metamorphism.