Gornergrat-Decke
Back to Gornergrat nappeRepresentation and status
- Color CMYK
- N/A
- Color RGB
- R: 241 G: 239 B: 237
- Rank
- tectonically bounded lithostratigraphic unit
- Validity
- Unit is in Use
- Status
- informal term
Nomenclature
- Deutsch
- Gornergrat-Decke
- Français
- Nappe du Gornergrat
- Italiano
- Falda del Gornergrat
- English
- Gornergrat Nappe
- Origin of the Name
- Historical Variants
-
Trias des Gornergrates = Gornergrat-Zone (Bearth 1953), Trias des Gornergrates = Normale Triasbedeckung des Altkristallins der Monte Rosa Teildecke (Rutsch et al. 1966), Gornergrat complex (Steck et al. 1979), Gornergrat-Serie (Bl. Randa, Müller 1983), Gornergrat zone (Lacassin 1984), Gornergrat Zone (Rubatto & Gebauer 1999), Gornergrat unit (Froitzheim 2001, Engi 2001, Ellis et al. 2016), Gornergrat nappe (De Meyer 2007), Gornergrat nappe = Gornergrat unit (Steck et al. 2015), Gornergrat-Decke (Bl. Saas), Gornergrat Nappe (TK500, Gouffon et al. 2024)
Description
- Description
-
Parautochton im Dach der Monte-Rosa-Decke ?+ polymetamorphic garnet-muscovite schist?
Steck et al. 2013 p.270: The sedimentary series in the Gornergrat area, formerly regarded as an integral part of the Monte Rosa nappe, have recently been recognized as an independent tectonic segment in front of the Stockhorn unit. Detailed stratigraphic and stuctural studies have recently lead the Lausanne group (lead by Albrecht Steck and Henri Masson) to identify several subunits, including the Mesozoic packages of the Cimes Blanches (Triassic? carbonate), the Gornergrat unit sensu stricto (Permotriassic, clastic), and the Tuftgrat unit (low to middle Jurassic, variable facies). Collectively, these subunits form a complexly folded wedge between the tectonically higher Zermatt-Saas unit and the Monte Rosa nappe. A detailed account of this new interpretation, based on several thesis projects, remains to be published.
- Thickness
- bis 300 m mächtiges Band
Hierarchy and sequence
- Units at roof
- Units at floor
Geography
- Geographical extent
- Gornergrat, Mittaghorn, Schwarzberg-Weisstor, Saas Fee.
Palaenography and tectonic
- Tectonic unit (resp. main category)
- Kind of protolith
-
- tectonic
References
- Definition
-
(2024) :
Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern
p.69: In the Val d’Anniviers, Zermatt Valley and Valtournanche, a few thin tectonic units are located at the contact between the Middle and Upper Penninic (Gornergrat Nappe) or are intercalated within the Tsaté Nappe (Frilihorn and Cimes Blanches 1) nappes). They are all composed of a series of Briançonnais-type Permian – Triassic sediments overlain by Jurassic breccias and limestone and calcschists probably of Cretaceous age. As their lithology is quite similar to that of the Mont Fort Nappe, their paleogeographic origin can also be located in the pre-Piemonte realm (transition zone between Briançonnais Terrane and Piemonte-Liguria Ocean); however, an Adriatic origin has also been proposed (“Austroalpine”, Dal Piaz 1999 and ref. therein). An eastward extension of the Mont Fort Nappe was often considered for these three narrow nappes (e. g., Argand 1909, Escher 1988, Pantet 2022).