Tasna-Decke
Back to Tasna nappeRepresentation and status
- Color CMYK
- N/A
- Color RGB
- R: 241 G: 239 B: 237
- Rank
- nappe
- Validity
- Unit is in Use
- Status
- valid
- Status discussion
Nomenclature
- Deutsch
- Tasna-Decke
- Français
- Nappe de Tasna
- Italiano
- Falda di Tasna
- English
- Tasna Nappe
- Origin of the Name
-
Val Tasna (GR), Unterengadin
- Historical Variants
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Tasna-Serie (Staub & Cadisch 1921, Cadisch 1932), Tasna-Serie, inkl. Tasna-Kreide (Cadisch 1947), Tasna Serie (Medwenitsch 1962), Tasna-Decke = Tasna-Serie (Cadisch et al. 1968, Friebe 2007), nappe de Tasna (Bousquet 1998), Tasna Nappe (TK500 / Gouffon et al. 2024)
- Nomenclatorial Remarks
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Geht im SE in die "Fimberzone" über.
Description
- Description
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Mächtige, verfaltete und verschuppte Platte, mit eine vollständige Schichtabfolge vom Kristallin bis ins Tertiär. Kristalliner Sockel mit fossiler Krust/Mantel-Grenze (Tasna-Granit bzw. Nauders-Ultrabasite).
Cadisch 1947: "3. Die Tasna-Serie erfüllt den ganzen restlichen Raum bis an den oberostalpinen Fensterrahmen. Ihre Schichtfolge umfasst Tasna-Altkristallin, Verrucano, Triasdolomit, Liaskalke mit Arieten, Malmkalk und eine vollständige Kreideserie, die weitgehend in Flyschfacies entwickelt ist. Serpentine treten in grossen Massen an der Deckenbasis auf, während diabasische Gesteine der oberen Kreide primär eingelagert sind. Die Tasna-Decke entspricht tektonisch der Falknis-Sulzfluh-Decke und der Aroser Schuppenzone Mittelbündens, d. h. dem Unterostalpin."
"Caractérisée par un «granite» vert, très hétérogène, avec des feldspaths potassiques, parfois rosés. Des granites assez semblables se trouvent à la base de la nappe de la Sulzfluh et, en galets, dans les sédiments mésozoïques du Falknis." Trümpy 1970 p.15
Age
- Age at top
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- Tertiary
- Age at base
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- Proterozoic
Geography
- Geographical extent
- Unterengadiner Fenster: Vorberge zwischen Val Sampuoir und Val Plavna, Ardez, Val Tasna, Val Urezzas, Val Urschai, Piz Minschun, Piz Tasna, Val Fenga / Fimbertal, Malfraga, Ladis / Kauns, sowie diskontinuierlisch zwischen Pradella, Sur En, Plattamala, ...
Palaenography and tectonic
- Paleogeography
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Briançonnais Terrane
:
microcontinent briançonnais
- Tectonic unit (resp. main category)
- Kind of protolith
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- tectonic
- Conditions of formation
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La série Liasique - Crétacé terminal est composée de turbidites associées à quelques calcaires pélagiques, correspondant à un environnement de talus continental (Waibel & Frisch, 1989).
References
- Definition
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(2024) :
Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern
p.76: In the western (Swiss) part of the Lower Engadine Window, the continental basement of the Tasna Nappe is stratigraphically overlain by Triassic to Jurassic sediments that have close similarities to those found in the Falknis Nappe (Gürler 1995). North of Ardez, the Early Cretaceous sequence contains black shales that could not yet be precisely dated. These shales are followed by Barremian breccias, mid-Cretaceous quartz-rich sediments and Couches Rouges, i. e., a sequence that is again similar to that of the Briançonnais-derived Falknis Nappe. The Cretaceous series is topped by Paleogene flysch. The Cretaceous – Paleogene sequence unconformably cover a former ocean-continent transition characterized by a detachment fault that exhumed subcontinental mantle (Florineth & Froitzheim 1994, Ribes et al. 2019).
In the northeastern (mostly Austrian) sector of the window, the Tasna Nappe ends and gives way to the Fimber Zone, which consists of a mélange formation dominated by Late Cretaceous to Paleogene flysch-type sediments. These contain tectonic slices and olistoliths of highly variable size and lithological composition; many of them are lithologically identical with basement and Mesozoic cover typical for the Tasna Nappe (Gruber et al. 2010). As this mélange contains quite a lot of ophiolitic bodies, the Fimber Zone – or at least a part of it – could also be correlated with the Arosa Zone.