The Geology of the Kloster Valley

 
From plate 13 you get a view east to the Arlberg with its green and wooded slopes. The underground consists of Silvretta Crystalline gneisses at the southern flank of the valley and the rugged steep slopes of the Northern Calcareous Alps at the northern flank of the valley.

As you already know from plate 2 “Linde” the sedimentary rocks were deposited on the crystalline basement of the Silvretta. The boundary between the gneisses and the sedimentary rocks was sheared off during alpine tectonics. The southern border of the Northern Calcareous Alps became steeply inclined and overturned as can be seen on the plate to the right. Because of the rocks’ low resistance to erosion, the Kloster Valley has been deeply cut into by the Alfenz River.

From the Obere Wies you see the sedimentary sequence of the Northern Calcareous Alps like an open book, with the oldest rocks in the valley floor and the youngest rocks at the peaks of the mountains. Weak rocks – like the Partnach and Raibl formations – build small plains in the normally steep slopes which are made up of the carbonate rocks of the Muschelkalk, Arlberg formation or Hauptdolomite. In addition, you can see a thin layering within the formations, especially within the Arlberg formation, which is repeated over and over again. The sedimentary layering was deformed along east-west and north-south striking folds.

Repeating the comparison from plate 2 “Linde”, you are standing in front of a stack of sandwiches, but despite your budding enthusiasm for geology, you’d be better off taking a bite of your own sandwich, rather than this layered stack of rocks! In the opposite rock wall of the Rote Wand, or Red Wall, you can see a red layer and some bright brown layers in the peak region. The red layer consists of radiolarite from the Jurassic era about 150 million years ago, which is made up of fossil silica algae. During the Neolithicum –the radiolarite was used by our ancestors to produce stone weapons and knives. Mining activity during the Stone-age has been proven in the Small Walser Valley a few kilometres to the north. The same rock is exposed at the peak of the Zimba, the highest peak of the Vandanser Steinwand or Vandans Stone Wall. The bright brown rocks consist of marls and are part of the youngest formation the so called “Kreideschiefer” or Chalk shale of the Northern Calcareous Alps in Vorarlberg and are about 150 million years old.

In the flat parts of the slope below the Obere Wies you can see gypsum carst or sink holes that were already explained earlier at the Bomatschies Forest.

If you were wondering where, at the opposite side of the valley, you can spot the red Verrucoan and Buntsandstein deposited during the period of desert climate- they are exposed in the deep cuts of the gullies like the “Höllentobel” or the “Muttentobel”. They are also exposed in the slopes above “Marias”.
The reason for the flat areas on the “Mustrinalpe” and below the peaks of the “Roggelskopf” and Gamsfreiheit on the steep face is that the underground there is made up of weak rocks from the Raibl formation that consists of clay stones, marls and gypsum.