Ötztal-Deckenkomplex

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

Nomenclature

Deutsch

Ötztal-Deckenkomplex

Français

Complexe de nappes de l'Ötztal

Italiano

Complesso di falde dell'Ötztal

English

Ötztal Nappe Complex

Origine du nom

Ötztal (Österreich)

Variantes historiques

Ötzthaler Masse (Stotter 1858), Oetztalerdecke (Eggenberger 1925), Ötztaliden (Medwenitsch 1962), Ötztal-Decke (Cadisch et al. 1968, Gruber et al. 2010), Ötztal-Scholle (Trümpy 1972), Oetztal nappe (Furrer et al. 1985), Ötztal-Einheit (Dössegger 1987), Ötztal Nappe Complex (TK500 / Gouffon et al. 2024)

Description

Description

Oberostalpines kristallines Deckenkomplex. Östliches Äquivalent der Silvretta-Decke.

Furrer et al. 1985: "This large body of basement rocks is overthrust along the gently E-dipping Schlinig thrust on the S-charl sediments and on intermediate slices. Towards the E, in Vinschgau (Italy), the separation between Oetztal, Sesvenna and Campo crystallines has not yet been mapped in detail. Klippen of Oetztal rocks occur in Val Müstair and around Umbrail pass; the general movement direction seems to be E-W. The Permian and Triassic rocks of the Jaggl, E of Reschen pass, are considered to represent a window of S-charl sediments under Oetztal crystallines."

Hiérarchie et succession

Unités hiérarchiquement subordonnées

• Matsch-Decke
• Ötztal-Decke

Géographie

Extension géographique

SE der Engadin-Störung

Région-type

Tirol (Österreich)

Paléogéographie et tectonique

Termes génériques

• Ötztal

Type de protolithe

• tectonique

Références

Révision

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

p.98: In the area of the Tectonic Map of Switzerland, only the western part of the Ötztal Nappe Complex is present. It consists of two lithologically and tectonically distinct units: the Ötztal Nappe forms the main part, and the smaller, overlying Matsch Nappe occurs in the Vinschgau area within the southern area of the nappe complex (Schmid & Haas 1989, Habler et al. 2009). The Ötztal Nappe consists mainly of polymetamorphic paragneisses with minor orthogneisses and amphibolites. At its western front, here lacking an Alpine metamorphic overprint, it overthrusts the S-charl-Sesvenna Nappe along the Schlinig Thrust, a discrete fault formed under brittle conditions. Froitzheim et al. (1997) claimed extensional overprint during the Late Cretaceous Ducan-Ela phase of what was originally a thrust contact, whereas Stutz & Walter (1983) see only compression, and Schmid & Haas (1989) interpret the extension leading to spectacular domino structures beneath the Schlinig Thrust as a secondary structure of the Ötztal Nappe overthrust. Southeast of Mals, the base of the Ötztal Nappe Complex is no longer a basal thrust fault, but changes to a broad shear zone (Vinschgau Shear Zone, § 8.2.6), due to the eastward increasing grade of metamorphism reaching higher greenschist-facies conditions (Schmid & Haas 1989). The Vinschgau Shear Zone consists mainly of rocks of the Campo Nappe Complex, but in its upper part the occurrence and thickness of the Variscan basement belonging to the Ötztal Nappe Complex cannot be defined, because of the close lithological similarities between the basements of the two nappe complexes in the immediate vicinity of the shear zone. The Ötztal Nappe Complex was thrust towards the WNW over the S-charl-Sesvenna Nappe far beyond the present-day location of the Schlinig Thrust and the Vinschgau Shear Zone, as indicated by isolated klippen of Ötztal basement overlying the S-charl-Sesvenna Nappe and the presence of Ötztal basement as part of the Umbrail-Chavalatsch Slices. Peak temperatures of Cretaceous metamorphism, associated with the top-WNW thrusting of the Ötztal Nappe Complex, were reached around 90 Ma ago (Thöni 1981).

The Matsch Nappe differs from the underlying Ötztal Nappe in that it is built up of a characteristic polymetamorphic (Variscan, Permian and Alpine) association of interlayered metapelites, amphibolites and pegmatites (Habler et al. 2009). Manifestations of Permian metamorphism, associated with the intrusion of pegmatites, are absent in the Ötztal Nappe, and hence thrusting of the Matsch Nappe over the Ötztal Nappe must be of early Alpine age, predating emplacement and metamorphism within the Ötztal Nappe Complex at around 90 Ma.