Salassic
Representation and status
- Color CMYK
- N/A
- Color RGB
- R: 241 G: 239 B: 237
- Rank
- tectonic domain
- Validity
- Unit is in Use
- Status
- valid
- Status discussion
Nomenclature
- Deutsch
- Salassikum
- Français
- Salassique
- Italiano
- Salassico
- English
- Salassic
- Origin of the Name
-
This term stems from a Celtic tribe, the Salasses, who settled in the Valle d’Aosta and the Sesia region, at the same time as the Helvetians north of the Alps and the Lepontians between Val d’Ossola and Leventina.
- Historical Variants
-
Cervinia (Froitzheim), sistema Sesia-Dent Blanche (Bearth 1980), Austro-Alpine thrust system of the Western Alps (dal Piaz 1993), Salassic (Gouffon et al. 2024)
Description
- Description
-
Die lithostratigraphische Einheiten die das Salassikum bilden stammen paläogeographisch aus ein Mikrokontinent im Piemont-Ligurischen Ozean.
Palaenography and tectonic
- Paleogeography
-
Cervinia Terrane
:
terrane or continental fragment
- 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.79: The Dent Blanche, Mont Mary and Sesia nappes in western Switzerland and adjacent Italy, together with the Margna and Sella nappes in southeastern Switzerland and partly in Italy, have an Adriatic paleogeographic affinity, as demonstrated by Staub (1917). However, their tectono-metamorphic history is quite different from those of the other Adriatic-derived units (Austroalpine and South Alpine domains). They show signs of high-pressure metamorphism as evidence of their subduction below the Austroalpine and South Alpine units (Froitzheim et al. 1996 b, Schmid et al. 2004, Handy et al. 2010) in Late Cretaceous times. Highpressure metamorphism in some of the Austroalpine nappes in Austria is older; the South Alpine units lack such an Alpine metamorphic overprint. On the other hand, the high-pressure metamorphism of the Upper Penninic units, derived from the Piemonte-Liguria Ocean, is Cenozoic (see § 6.2.3), and therefore younger than that of the nappes mentioned above.
These particular continent-derived basement units are interpreted as originating from a continental fragment that split off from the most distal part of the Adriatic margin during the Middle Jurassic opening of the Piemonte-Liguria Ocean. This extensional allochthon is referred to as the Cervinia Terrane (Pleuger et al. 2007, Froitzheim et al. 2008; see Pl. III) or the Margna-Sesia fragment (Schmid et al. 2004).
Because of their Adriatic affinity, these tectonic units are classically attributed to the Austroalpine. The Dent Blanche, Mont Mary and Sesia nappes, situated in the Western Alps, are sometimes grouped together under the term of “Austroalpine tectonic system of the Western Alps” (Dal Piaz & Ernst 1978, Bigi et al. 1990). As they occupy a transitional position between the Austroalpine and the Penninic, they have also been attributed to the Upper Penninic (Froitzheim et al. 2008) or to a subdomain called “Ultrapenninic” (Trümpy 1992).
Given the ambivalence regarding their attribution and the specificity of their tectono-metamorphic history, it seems appropriate to group the tectonic units derived from this extensional allochthon into a new domain (1st order, see § 1.1.1) called “Salassic”. This term stems from a Celtic tribe, the Salasses, who settled in the Valle d’Aosta and the Sesia region, at the same time as the Helvetians north of the Alps and the Lepontians between Val d’Ossola and Leventina.
Material and varia
