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 ~ | |
| 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°41′46″N 6°44′04″E / 45.696144°N 6.734438°E |
| Region | Savoie |
| Country |  France Switzerland |
| Type section | |
| Named for | L’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) 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
edit- ^ 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.
- ^ 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.
- ^ "Couches des Marmontains". Lithostratigraphisches Lexikon der Schweiz. Retrieved 25 February 2013.
- ^ 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.
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