Laas-Decke
Back to Laas NappeRepresentation and status
- Color RGB
- R: 241 G: 239 B: 237
- Rank
- nappe
- Validity
- Unit is in Use
- Status
- valid
Nomenclature
- Deutsch
- Laas-Decke
- Français
- Nappe de Laas
- Italiano
- Falda di Laas
- English
- Laas Nappe
- Origin of the Name
-
Laas = Lasa (Italia), Val Venosta
- Historical Variants
-
Laaser Einheit (Mair et al. 2007), Laas Nappe (TK500 / Gouffon et al. 2024)
Description
- Description
-
Oberostalpine Decke ...
Palaenography and tectonic
- Tectonic unit (resp. main category)
- Kind of protolith
-
- tectonic
- Metamorphism
- metamorphic
References
- Definition
-
(2024) :
Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern
p.95: The Laas Nappe (“Laaser Einheit” of Mair et al. 2007) exposes a series of often subvertically northward inclined garnet and staurolite bearing paragneisses, marbles and amphibolites metamorphosed under amphibolite-facies conditions during the Variscan orogeny (Martin et al. 2009). Cretaceous metamorphic overprint varies from greenschist facies in the west to lower amphibolite facies in the east (Schmid & Haas 1989). This nappe occupies a much-debated and still unclear position in the Upper Austroalpine nappe pile. It is considered a part of the so-called “Ortler-Campo basement” by Mair et al. (2007), who suggest that there is no Alpine tectonic separation between the Ortler and Campo nappes. However, as described below, the Ortler Nappe overlies the Campo and the Laas nappes along the Zebrù Thrust (Conti et al. 1994, Conti 1997) and thus occupies a tectonically higher position. On the other hand, the Laas Nappe is also separated from the Campo Nappe (the “Pejo-Einheit” of Mair et al. 2007) by a sliver of Mesozoic cover of the Laas Nappe along a steeply S-dipping thrust (“Laaser Linie” of Mair et al. 2007). Additionally, the distinctly different lithological composition of the basement of the Laas Nappe in respect to that of the Campo Nappe justifies its separation as a distinct nappe. In view of the considerations above, the Laas Nappe is here considered a distinct part of the Campo Nappe Complex. The steeply S-dipping basal E–W striking thrust of the Laas Nappe, oriented perpendicular to the Cretaceous-age Alpine metamorphic zonation, very probably represents a top-N out-of-sequence thrust of Cenozoic age that brings the Campo Nappe over the Laas Nappe. To the north, the Laas Nappe is overlain by the very shallowly N-dipping Cretaceous Vinschgau Shear Zone, located just below the tectonically higher Ötztal Nappe. This indicates that the Laas Nappe was previously in a tectonically higher structural position within the Campo Nappe Complex during the Late Cretaceous top-WNW thrusting.