The Couches de l’Aroley (short: Aroley Formation) are a sedimentary formation deposited during the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

(

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

). They consist of calcitic

schist Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced ''schistosity'' (named for the rock). This means that the rock is composed of mineral grains easily seen with a l ...

s 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 The Valais Ocean is a subducted oceanic basin which was situated between the continent Europe and the microcontinent Iberia or so called Briançonnais microcontinent. Remnants of the Valais ocean are found in the western Alps and in tectonic win ...

. 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 The Saxons, sometimes called the Old Saxons or Continental Saxons, were a Germanic people of early medieval "Old" Saxony () which became a Carolingian " stem duchy" in 804, in what is now northern Germany. Many of their neighbours were, like th ...

Valais Valais ( , ; ), more formally, the Canton of Valais or Wallis, is one of the cantons of Switzerland, 26 cantons forming the Switzerland, Swiss Confederation. It is composed of thirteen districts and its capital and largest city is Sion, Switzer ...

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

. The formation is named after a "Plan Aroley" which lies below the Pierre Avoi. It was first described by

Rudolf Trümpy Rudolf Trümpy (16 August 1921 – 30 January 2009) was a Swiss geologist, who was born in the small Swiss town of Glarus. He graduated from the ETH Zürich in the late 1940s with a thesis titled: “Der Lias der Glarner Alpen”. From 1947 to 1953 ...

1952. The Couches de l’Aroley can be correlated with the Klus Formation and the Tristel Formation found in eastern

, the

Engadin window The Engadin window or (Lower Engadin window) is a tectonic window that exposes penninic units lying below the austroalpine units in the alpine orogeny, alpine nappe stack. It has a roughly elliptical shape with the long axis striking northwest-so ...

and the Tauern window.

References

{{Reflist Geologic formations of France Geologic formations of Switzerland Lower Cretaceous Series of Europe Cretaceous France Cretaceous Switzerland Barremian Stage Geology of the Alps Schist formations