Marmontains Formation
From Wikipedia, the free encyclopedia
The Couches des Marmontains are a sedimentary formation deposited during the middle Cretaceous (Albian to Cenomanian). It consists of sandstones and black shales. The formation is 5 to 30 m thick.[1] The Couches des Marmontains overly the Couches de l’Aroley and underlie the Couches de Saint Christophe. All three units together make up the post-rift sequence of the Valais ocean. Outcrops can be found north of Bourg-Saint-Maurice.[2]
Couches des Marmontains | |
---|---|
Stratigraphic range: Albian-Cenomanian ~112–94 Ma | |
Type | Geological formation |
Unit of | Valais trilogy |
Underlies | Couches de Saint Christophe |
Overlies | Couches de l’Aroley |
Thickness | 5 to 30 m (16 to 98 ft) |
Location | |
Coordinates | 45.696144°N 6.734438°E / 45.696144; 6.734438 |
Region | Savoie |
Country | France Switzerland |
Type section | |
Named for | L’arête des Marmontains |
The Couches des Marmontains can be found in the following nappes:
- External Valais
- Moûtiers unit
- Roc de l'Enfer unit
- Petit St. Bernard unit
- Internal Valais
- Versoyen unit
The type locality and namesake of the formation is the mountain Marmontains (45.88263°N 7.108412°E / 45.88263; 7.108412) and the Val Ferret in Orsières, Canton Valais, Switzerland. It was first described in 1955 by Rudolf Trümpy.[3]
The Marmontains Formation can be correlated with the Valzeina Formation of Graubünden and black shales in the Engadine.[4]