Silvretta-Decke

Représentation et statut

Couleur CMYK

N/A

Couleur RGB

R: 241 G: 239 B: 237

Rang

nappe

Usage

Ce terme est en usage.

Status

valide

Discussion du statut

Nomenclature

Deutsch

Silvretta-Decke

Français

Nappe de la Silvretta

Italiano

Falda della Silvretta

English

Silvretta Nappe

Origine du nom

Silvretta-Gebirgsgruppe (GR)

Variantes historiques

Silvretta-Masse (Stotter 1858), Silvrettamasse (Koch 1875, Koch 1876a, Koch 1877a/b), Silvrettadecke (Staub & Cadisch 1921, Ott 1922), oberostalpine Decke = Silvretta-Decke (Alb. Heim 1922), Silvrettiden (Medwenitsch 1962), Silvretta-Scholle = Silvretta-Schubmasse (Trümpy 1972), Silvretta-Masse = Silvrettadecke (Kräyenbühl 1984), Silvretta-Einheit (Dössegger 1987), Silvretta nappe (Maggetti & Flisch 1993), Silvretta thrust sheet (Biino 1996), Silvretta-Decke (Gruber et al. 2010, Furrer et al. 2015), Silvretta Nappe (TK500 / Gouffon et al. 2024)

Remarques nomenclatoriales

die Silvretta

Description

Description

Oberostalpine Decke mit polymetamorphes Altkristallin (inkl. variszisch steilgestellten Schlingen), postvariszische Diabasgänge, sowie permo-mesozoische Sedimentbedeckung im SE (Ducan- und Landwassergebiet).

Furrer et al. 1985: "This is another large thrust mass of basement rocks, similar in many respects to the Oetztal nappe. Triassic sediments are preserved only near its western margin, where they occur in SW-NE trending synclines; the NW ("normal") flank of these is often cut by lags. These (early?) Alpine folds as well as the Variscan and pre-Variscan basement structures are truncated by the basal thrust, implying important E-W movements. The base of the nappe is further deformed by E-W trending synforms and antiforms."

Épaisseur

Maximal 5 km dicke Platte.

Hiérarchie et succession

Unités hiérarchiquement subordonnées

• Ducan-Synklinal
• Landwasser-Synklinal
• «Phyllitgneiszone»
• Kristallines Grundgebirge der Silvretta-Decke

Limite supérieure

Ötztal-Decke, Nördliche Kalkalpen (mit Landecker Phyllitgneiszone am Übergang)

Limite inférieure

Arosa-Decke bzw. Flysch der Tasna-Decke (Bollin 1989), Subsilvrettide Schollen, Err-Bernina-Deckenkomplexe, Ela-Decke, Engadiner Störung

Géographie

Extension géographique

Verwall- und Samnaungruppe.

Paléogéographie et tectonique

Paléogéographie

marge continentale adriatique :

southern continental margin / platform

Termes génériques

• Silvretta

Type de protolithe

• tectonique

Métamorphisme

polycyclique (alpin, varisque et plus ancien)

Faciès métamorphique

• faciès à schistes verts (épizone)
• faciès à amphibolites

Remarque sur le facies

prävariszische Metamorphose (Maggetti & Galetti 1988, Frank et al. 1978), variszische (360-350 Ma) Amphibolit-fazielle Metamophose, gefolgt von einer späteren (310-300 Ma) Grünschiefer-faziellen Metamorphose (Flisch 1987)

Références

Révision

Gouffon Yves (Editor) (2024) : Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern

p.92: The Silvretta Nappe is the northernmost Upper Austroalpine basement-cover nappe extending over a large area located between the southern rim of the Northern Calcareous Alps in the north and the Engadine Fault in the south. Most of its area is occupied by high-grade metamorphic basement that was multiply deformed since the Precambrian, ending with an amphibolite-facies Variscan tectono-metamorphic event in the Carboniferous (Magetti & Flisch 1993). A top-N Alpine thrust of secondary importance separates this high-grade basement from a narrow belt of low-grade basement referred to as the “Phyllitgneiszone” (including the Landeck Quartzphyllites) that is nowadays also considered to be a part of the Silvretta Nappe (Gruber et al. 2010). It has a lower grade of pre-Alpine metamorphism and has been intensely sheared during the Alpine orogeny (Rockenschaub 1990).
The Triassic cover of the Silvretta Nappe is preserved in two SW– NE striking synclines located at the western edge of the Silvretta Nappe, known as the Landwasser and Ducan synclines (Froitzheim et al. 1994). They formed during top-NW thrusting in the Cretaceous, and then were overprinted by normal faulting still in the latest Cretaceous. This was followed by top-N thrusting of the entire Silvretta Nappe over the Penninic units during Cenozoic times. Only very small lenses of Permo-Carboniferous and Early Triassic slivers (“Puschlin Zone”) are preserved within the Landeck Quarzphyllites (Gruber et al. 2010).