Rossa-Orthogneis

Retour à nappe de l'Adula

Représentation et statut

Couleur CMYK
(0%,35%,29%,4%)
Couleur RGB
R: 245 G: 160 B: 175
Rang
Formation lithostratigraphique
Usage
Ce terme est en usage.
Status
terme local (informel)

Nomenclature

Deutsch
Rossa-Orthogneis
Français
Orthogneiss de Rossa
Italiano
Ortogneiss di Rossa
English
Rossa Orthogneiss
Origine du nom

Rossa (GR)

Variantes historiques

Rossa Orthogneiss (Cavargna-Sani 2013 p.35)

Âge

Âge au sommet
  • Ordovicien tardif
Âge à la base
  • Ordovicien tardif
Méthode de datation

459.3 +3.4/-1.7 Ma, 455.7 +2.6/-2.7 Ma (Cavargna-Sani 2013)

Références

Définition
Cavargna-Sani Mattia (2013) : The Adula nappe: stratigraphy, structure and kinematics of an exhumed high-pressure nappe. Thèse de doctorat, Université de Lausanne, 153 p.

p.35: The Rossa Orthogneiss and the Garenstock Augengneiss are considered separately because they are not connected in outcrop. They both have the same Ordovician age (Chapter 3.5). The Rossa Orthogneiss texture is usually fine-grained and does not exhibit the characteristic augengneiss texture typical of the Garenstock gneiss. However, some K-feldspar phenocrysts can be locally observed. Mafic boudins are rarely present, and eclogites were not found. Descriptions of this formation can be found in Frischknecht (in Jenny et al. 1923) and Kündig (1926). Frischknecht proposes a distinction between orthogneisses based on biotite content. However, the biotite content is strongly related to metamorphic grade (Spear 1995) and therefore cannot be used in the formation definition.

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