zona di Gresso-Someo

Représentation et statut

Couleur CMYK

N/A

Couleur RGB

R: 200 G: 225 B: 250

Rang

zone tectonique

Usage

Ce terme est en usage.

Status

valide

Nomenclature

Deutsch

Gresso-Someo-Zone

Français

zone de Gresso-Someo

Italiano

zona di Gresso-Someo

English

Gresso-Someo zone

Origine du nom

Gresso (TI) e Someo (TI)

Variantes historiques

Someo-Mulde (Niggli et al. 1936), Zug von Gresso (Kobe 1954), Someo unit p.p. (Berger et al. 2005), Someo zone (Steck et al. 2013)

Remarques nomenclatoriales

non: Someo gneiss (Köppel et al. 1980) = Paragneis der Maggia-Decke

Description

Description

... an der Grenze zwischen Antigorio- und Maggia-Decke (bzw. Nordgrenze der Mergoscia-Zone nach Zawadynski 1952 und Dal Vesco 1953).

Épaisseur

Max. gegen 30 m südlich Gresso (Kobe 1954)

Hiérarchie et succession

Limite supérieure

Mergoscia-Decke

Limite inférieure

Maggia-Decke

Âge

Âge au sommet

• Mésozoïque

Âge à la base

• Mésozoïque

Méthode de datation

ehem. Trias?, eher Mittlerer und Oberer Jura ?

Géographie

Extension géographique

Lepontin: Someo, Brontallo, Gresso.

Références

Révision

Steck Albrecht, Della Torre F., Keller Franz, Pfeifer Hans-Rudolf, Hunziker Johannes, Masson Henri (2013) : Tectonics of the Lepontine Alps : ductile thrusting and folding in the deepest tetonic levels of the Central Alps. Swiss Journal of Geosciences, 106/3, 427-450

p.435: The term Someo zone is defined and restricted in this paper in accordance with Preiswerk et al. (1934) to a decimetre to some metres thick band of white calcite marble and associated quartzite, micaschist and amphibolite that marks the limit between the Mergoscia and Maggia units. It is not possible to attribute this zone to one of the two adjacent units. The Someo zone is composed north of Someo of an up to 4 m thick band of white calcite marble. At its border it is associated with centimetre to decimetre thick bands of quartzite, amphibolite and some garnet micaschist. Two bands of up to 60 cm thick white calcite marble are associated with garnet micaschist and decametric bands of amphibolite in the Maggia riverbed southeast of Brontallo (Fig. 2; Keller et al. 1980). Eclogite relicts are missing in the amphibolite layers of Someo and Brontallo. The new definition of the Someo unit by Berger et al. (2005), who associate in the Someo unit the marbles of Preiswerk’s Someo zone with the gneiss, schists, eclogitic amphibolites, ultramafites and marbles of our herein defined Mergoscia unit, is for this reason rejected and replaced by the original definition of Preiswerk et al. (1934). It is speculated that the white marble of the otherwise very different Fusio, Pertusio and Someo sedimentary sequences may belong to a same possibly Upper Jurassic marble horizon of the Sambuco–Maggia nappe.