Grand Fond Group

Brèches du Grand Fond Group
Stratigraphic range: Middle Jurassic
Type Geological group
Sub-units Pyramides Calcaires Formation
Dent d'Arpire Formation
Underlies Couches de l’Aroley
Overlies Basement (Valais pre-rift)
Lithology
Primary Conglomerate of pre-rift rocks.
Location
Coordinates 45°41′46″N 6°44′04″E / 45.696144°N 6.734438°E / 45.696144; 6.734438Coordinates: 45°41′46″N 6°44′04″E / 45.696144°N 6.734438°E / 45.696144; 6.734438
Region Savoie
Country France

The Brèches du Grand Fond Group is a group of stratigraphic formations in France that were deposited between the Middle Jurassic and the Early Cretaceous. The deposition was contemporaneous to the rifting of the Valais ocean, and overlies the pre-rift rocks along an angular unconformity. The Brèches du Grand Fond Group is overlain by the post-rift sequences Couches de l’Aroley, Couches des Marmontains and the Couches de Saint Christophe.[1]

The Brèches du Grand Fond Group consists of two formations that are found in the External Valais units, the younger Pyramides Calcaires Formation and the older Dent d'Arpire Formation. The deposition of these two units was roughly contemporaneous to the deposition of the Brèches du Collet des Rousses and the Complexe Antéflysch Formation of the Internal Valais units.[1]

In general the Brèches du Grand Fond Group consists of coarse grained clastic sediments composed of pre-rift lithologies. Outcrops can be studied [1][2]

The Brèches du Grand Fond Group can be found within the following nappes:[1]

  • External Valais
  • Moûtiers unit
  • Roc de l'Enfer unit

Outcrops occur to the northwest of Bourg-Saint-Maurice.[1]

References

  1. 1 2 3 4 5 Loprieno, Andrea (2011). "The Valais units in Savoy (France): a key area for understanding the palaeogeography and the tectonic evolution of the Western Alps".
  2. ↑ Loprieno, Andrea. "http://earth.unibas.ch/tecto/research/Diss_Loprieno_2001_small.pdf" (PDF). Retrieved 21 February 2013. External link in |title= (help)
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