Couches des Marmontains
Stratigraphic range: Albian-Cenomanian
~
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 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:

  • 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°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

  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)
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