Couches de Saint Christophe
Stratigraphic range: Late Cretaceous-Paleogene
TypeGeological formation
Unit ofValais trilogy
OverliesCouches des Marmontains
ThicknessAveraging 500 m (1,600 ft)
Lithology
PrimarySchist
OtherCalcitic sandstone
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 forChapel St. Christophe, Verbier

The Couches de Saint Christophe are a sedimentary formation deposited between the Late Cretaceous and the Paleogene. It is a very monotonous sequence of calcitic sandstones and black schists. These are interpreted as a turbidite sequence. The average thickness of the unit is 500 m.[1] The Couches de Saint Christophe are a post-rift sequence that overlies the Couches des Marmontains.[2]

The Couches de Saint Christophe occupy the following nappes:[2]

  • External Valais
  • Moûtiers unit
  • Roc de l'Enfer unit
  • Petit St. Bernard unit
  • Internal Valais
  • Versoyen unit

Large outcrops of the Couches de Saint Christophe crop out north of Bourg-Saint-Maurice.[2]

The type locality of the formation is the Val de Bagnes in the canton Valais of Switzerland. It was first described by Rudolf Trümpy in 1952. The formation is named after a chapel (46°05′42″N 7°12′01″E / 46.094905°N 7.200371°E / 46.094905; 7.200371) to the northwest of Verbier.[3]

The Saint Christophe Formation can be correlated with the Sassauna Formation found in Graubünden and calcareous flysch found 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. University of Basel. Archived from the original (PDF) on 6 March 2016. Retrieved 6 June 2023.
  2. 1 2 3 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. ↑ "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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