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
TypeGeological formation
Unit ofValais trilogy
UnderliesCouches de Saint Christophe
OverliesCouches de l’Aroley
Thickness5 to 30 m (16 to 98 ft)
Location
Coordinates45°41′46″N 6°44′04″E / 45.696144°N 6.734438°E / 45.696144; 6.734438
RegionSavoie
Country France
 Switzerland
Type section
Named forL’arête des Marmontains

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. 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]

References

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  1. ^ Loprieno, Andrea (2001). "A combined structural and sedimentological approach to decipher the evolution of the Valais domain in Savoy, (Western Alps)" (PDF). earth.unibas.ch.
  2. ^ Loprieno, Andrea (2011). "The Valais units in Savoy (France): a key area for understanding the palaeogeography and the tectonic evolution of the Western Alps". International Journal of Earth Sciences. 100 (5): 963. Bibcode:2011IJEaS.100..963L. doi:10.1007/s00531-010-0595-1. hdl:20.500.11850/37751. S2CID 56379732.
  3. ^ "Couches des Marmontains". Lithostratigraphisches Lexikon der Schweiz. Retrieved 25 February 2013.
  4. ^ Tricart, Pierre-Charles de Graciansky, David G. Roberts, Pierre (2010). The Western Alps, from rift to passive margin to orogenic belt : an integrated geoscience overview (1st ed.). Amsterdam: Elsevier. p. 153. ISBN 978-0444537249.{{cite book}}: CS1 maint: multiple names: authors list (link)