| Couches des Marmontains | |
| Period: | Cenomanian |
| Age: | Albian-Cenomanian ~ |
| Type: | Geological formation |
| Namedfor: | L’arête des Marmontains |
| Region: | Savoie |
| Country: | |
| Unitof: | Valais trilogy |
| Underlies: | Couches de Saint Christophe |
| Overlies: | Couches de l’Aroley |
| Thickness: | 5to |
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]
The Couches des Marmontains can be found in the following nappes:
The type locality and namesake of the formation is the mountain Marmontains 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]