Portjengrat-Decke
Rappresentazione e statuto
- Colore CMYK
- N/A
- Colore RGB
- R: 241 G: 239 B: 237
- Rango
- falda
- Uso
- Unità in uso.
- Status
- valido
Nomenclatura
- Deutsch
- Portjengrat-Decke
- Français
- Nappe du Portjengrat
- Italiano
- Falda del Portjengrat
- English
- Portjengrat Nappe
- Origine del nome
- Varianti storiche
-
pli du Portjengrat (Argand 1911b), oberer nördlicher Lappen (der Monte Rosadecke) = Pli du Portjengrat = Portjengratlappen (Eichenberger 1926), Portjengrat-Lappen (Blumenthal 1952, Müller 1983), lembo del Portjengrat (Dal Piaz et al. 1992a), unité du Portjengrat = zone du Portjengrat (Carrupt & Schlup 1998), Portjengrat Nappe (TK500, Gouffon et al. 2024)
Descrizione
- Descrizione
-
... replissée dans la nappe d'Antrona.
Referenze
- Revisione
-
(2024) :
Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern
p.66: The Portjengrat Nappe, exposed east of Saas Fee, occupies a special position as a buffer zone between the Siviez-Mischabel and Monte Rosa nappes on the one side and between the Zermatt - Saas Fee and Antrona nappes on the other side. It consists mainly of a crystalline basement resembling that of the Siviez-Mischabel and Monte Rosa nappes, overlain by a very thin Mesozoic sedimentary cover. Both basement and cover are crosscut by mafic veins, such as in the adjacent “Furgg Zone” (§ 6.2.2.6). The Portjengrat Nappe was related either to the Monte Rosa Nappe (e.g., Argand 1911), which underwent the same Alpine high-pressure metamorphism, or to the Siviez-Mischabel Nappe (e. g., Bearth 1939), with which it is in apparent tectonic continuity but which exhibits Alpine metamorphism only under greenschist-facies conditions. Steck et al. (2015) categorize it as an independent tectonic unit. The Portjengrat Nappe is separated from the Monte Rosa Nappe by the “Furgg Zone”, considered here as the sedimentary cover of the Monte Rosa Nappe (§ 6.2.2.6). The contact with the Siviez-Mischabel Nappe is difficult to map in the field, because no metasediments are observed between the gneisses of each of these two units; Steck et al. (2015) trace it along a shear zone.