The Couches des Marmontains are a sedimentary formation deposited during the middle Cretaceous (Albian to Cenomanian).

It consists of sandstones and black shales.

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 (45°52′57″N 7°06′30″E / 45.88263°N 7.108412°E / 45.88263; 7.108412) and the Val Ferret in Orsières, Canton Valais, Switzerland.