Rossa-Orthogneis

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Representation 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
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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