«Ultrahelvétique»
Back to HelveticRepresentation and status
- Color CMYK
- N/A
- Color RGB
- R: 236 G: 234 B: 232
- Rank
- tectonic domain
- Validity
- Unit is in Use
- Status
- valid
- Status discussion
Nomenclature
- Deutsch
- «Ultrahelvetikum»
- Français
- «Ultrahelvétique»
- Italiano
- «Ultraelvetico»
- English
- «Ultrahelvetic»
- Historical Variants
-
--- (Heim 1921), nappes ultrahelvétiques, Hochhelvetikum p.p. (Allemann & Blaser 1951), Ultrahelvetische Decken (Trümpy 1974), exotic cover sediments (Milnes & Pfiffner 1977), exotische Einheiten [des Infrahelvetikums] (Pfiffner 1978), Ultraelvetico (Dal Piaz et al. 1992a), Ultrahelvetic (TK500 / Gouffon et al. 2024)
- Nomenclatorial Remarks
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Wildflyschdecke (Arn. Heim 1908), Préalpes externes, Préalpes bordières (Gagnebin 1924)
Description
- Description
-
"mélanges dont l'origine est pro parte sédimentaire (olistostromes), pro parte tectonique (méga-mylonites), sans que la part des deux processus soit précisèment établie" [www.geol-alp.com]
Jeanbourquin et al. 1992 p.66: [...] le terme «ultrahelvétique» désigne d'une part un ensemble d'écaillés posé sur le dos de la nappe du Wildhorn (Heim 1921) et d'autre part un bassin ou une aire paléogéographique (e.g., Trümpy 1980, Badoux 1988).
Palaenography and tectonic
- Paleogeography
- Ultrahelvetic Domain
- Tectonic unit (resp. main category)
- Kind of protolith
-
- tectonic
- Conditions of formation
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bassin
References
- Definition
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(2024) :
Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern
p.31: East of the Thunersee, the boundary between the Lower Helvetic and the Upper Helvetic is formed by major out-of-sequence thrusts of the second [deformation] phase, which cut the entire structural framework formed during the first phase; from west to east these are the Axen and the Glarus thrusts. As a consequence of this out-of-sequence thrusting, units of Ultrahelvetic origin are now found both above and below these major thrust faults, i. e., in the Upper Helvetic and in the Lower Helvetic subdomains, respectively.
West of the Thunersee, the early detached sediments of the Ultrahelvetic realm crop out in various positions: 1) on top of the Lower and Upper Helvetic nappes, 2) in a wide band between the Helvetic nappes and the Penninic units of the Prealps and 3) between the Subalpine Molasse and the Prealps nappes. The 2nd phase Diablerets and Wildhorn thrusts cut across the older basal thrust of these “Ultrahelvetic” units (Jeanbourquin 1994, Steck et al. 2001, Pfiffner et al. 2010) in the same way as the out-of-sequence thrusts east of the Thunersee. Consequently, the units originated from the Helvetic platform and situated below the Diablerets and Wildhorn thrusts belong to the Lower Helvetic and those above these thrusts to the Upper Helvetic domain. As the Diablerets and Wildhorn thrusts have a significantly smaller displacement (10–15 km) compared to the Axen Thrust (20–25 km) and Glarus Thrust (30 – 35 km) in the east (Pfiffner 2011), not all the units of Ultrahelvetic origin are involved and thus cannot be allocated to either the Upper or Lower Helvetic. For this reason, they are all considered as Upper Helvetic west of the Thunersee and are included in the Pillon and Bulle mélange zones (see § 4.2.7 and 4.2.8).
- Important Publications
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(1921) : Geologie der Schweiz, Bd.2a: die Schweizer Alpen.(1943) : Une nouvelle hypothèse tectonique: la diverticulation. Bull. Soc. vaud. sci. nat. 62/260, 301-