Aroley Formation

Couches de l’Aroley
Stratigraphic range:
Pierre Avoi is the type locality of the Aroley formation.
Type	Geological formation
Unit of	Valais trilogy
Underlies	Couches des Marmontains
Overlies	Brèches du Grand Fond Group
Thickness	Average of 100 m
Lithology
Primary	Calcitic schist
Other	Fine conglomerate
Location
Coordinates	45.696144°N 6.734438°E / 45.696144; 6.734438
Region	Savoie
Country	France
Type section
Named for	Plan Aroley

The Couches de l’Aroley (short: Aroley Formation) are a sedimentary formation deposited during the Early Cretaceous (Barremian to Aptian). They consist of calcitic schists with dolomite clasts interbedded with finegrained conglomerates. The whole sequence is about 100 m thick.

The Couches de l’Aroley are the lowest of the three post-rift sequences deposited in the Valais ocean. It overlies syn-rift sequences of the Brèches du Grand Fond Group.

The Aroley Formation can be found within the following nappes:

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

The type locality is the Massif de la Pierre Avoi, in Saxon, Valais, Switzerland. The formation is named after a "Plan Aroley" which lies below the Pierre Avoi. It was first described by Rudolf Trümpy 1952.

The Couches de l’Aroley can be correlated with the Klus Formation and the Tristel Formation found in eastern Switzerland, the Engadin window and the Tauern window.