Saint Christophe Formation

Couches de Saint Christophe Stratigraphic range: Late Cretaceous PreЄ Є O S D C P T J K Pg N
Type	Geological formation
Unit of	Valais trilogy
Overlies	Couches des Marmontains
Thickness	Average of 500 m
Lithology
Primary	Schist
Other	Calcitic Sandstone
Location
Coordinates	45°41′46″N 6°44′04″E / 45.696144°N 6.734438°ECoordinates: 45°41′46″N 6°44′04″E / 45.696144°N 6.734438°E
Region	Savoie
Country	France
Type section
Named for	Chapel 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) 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. "http://earth.unibas.ch/tecto/research/Diss_Loprieno_2001_small.pdf" (PDF). Retrieved 21 February 2013. External link in |title= (help)
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".
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.