zona di Gresso-Someo
Back to Maggia nappeRepresentation and status
- Color CMYK
- N/A
- Color RGB
- R: 200 G: 225 B: 250
- Rank
- tectonic zone
- Validity
- Unit is in Use
- Status
- valid
Nomenclature
- Deutsch
- Gresso-Someo-Zone
- Français
- zone de Gresso-Someo
- Italiano
- zona di Gresso-Someo
- English
- Gresso-Someo zone
- Origin of the Name
- Historical Variants
-
Someo-Mulde (Niggli et al. 1936), Zug von Gresso (Kobe 1954), Someo unit p.p. (Berger et al. 2005), Someo zone (Steck et al. 2013)
- Nomenclatorial Remarks
-
non: Someo gneiss (Köppel et al. 1980) = Paragneis der Maggia-Decke
Description
- Description
-
... an der Grenze zwischen Antigorio- und Maggia-Decke (bzw. Nordgrenze der Mergoscia-Zone nach Zawadynski 1952 und Dal Vesco 1953).
- Thickness
- Max. gegen 30 m südlich Gresso (Kobe 1954)
Hierarchy and sequence
- Upper boundary
-
Mergoscia-Decke
- Lower boundary
-
Maggia-Decke
Age
- Age at top
-
- Mesozoic
- Age at base
-
- Mesozoic
- Dating Method
-
ehem. Trias?, eher Mittlerer und Oberer Jura ?
Geography
- Geographical extent
- Lepontin: Someo, Brontallo, Gresso.
References
- Definition
-
(2013) :
Tectonics of the Lepontine Alps : ductile thrusting and folding in the deepest tetonic levels of the Central Alps. Swiss Journal of Geosciences, 106/3, 427-450
p.435: The term Someo zone is defined and restricted in this paper in accordance with Preiswerk et al. (1934) to a decimetre to some metres thick band of white calcite marble and associated quartzite, micaschist and amphibolite that marks the limit between the Mergoscia and Maggia units. It is not possible to attribute this zone to one of the two adjacent units. The Someo zone is composed north of Someo of an up to 4 m thick band of white calcite marble. At its border it is associated with centimetre to decimetre thick bands of quartzite, amphibolite and some garnet micaschist. Two bands of up to 60 cm thick white calcite marble are associated with garnet micaschist and decametric bands of amphibolite in the Maggia riverbed southeast of Brontallo (Fig. 2; Keller et al. 1980). Eclogite relicts are missing in the amphibolite layers of Someo and Brontallo. The new definition of the Someo unit by Berger et al. (2005), who associate in the Someo unit the marbles of Preiswerk’s Someo zone with the gneiss, schists, eclogitic amphibolites, ultramafites and marbles of our herein defined Mergoscia unit, is for this reason rejected and replaced by the original definition of Preiswerk et al. (1934). It is speculated that the white marble of the otherwise very different Fusio, Pertusio and Someo sedimentary sequences may belong to a same possibly Upper Jurassic marble horizon of the Sambuco–Maggia nappe.