Rossa-Orthogneis
Back to Adula NappeRepresentation and status
- Color CMYK
- (0%,35%,29%,4%)
- Color RGB
- R: 245 G: 160 B: 175
- Rank
- lithostratigraphic Formation
- Validity
- Unit is in Use
- Status
- local name (informal)
Nomenclature
- Deutsch
- Rossa-Orthogneis
- Français
- Orthogneiss de Rossa
- Italiano
- Ortogneiss di Rossa
- English
- Rossa Orthogneiss
- Origin of the Name
-
Rossa (GR)
- Historical Variants
-
Rossa Orthogneiss (Cavargna-Sani 2013 p.35)
Age
- Age at top
-
- Late Ordovician
- Age at base
-
- Late Ordovician
- Dating Method
-
459.3 +3.4/-1.7 Ma, 455.7 +2.6/-2.7 Ma (Cavargna-Sani 2013)
References
- Definition
-
(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.