Gargellen window

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Geological map sketch of the Gargellen window (window heavily framed)

Gargellenfenster is the geological name for a tectonic window in Vorarlberg , in which rock units of the Penninic under the tectonically overlapping crystalline of the Eastern Alps are exposed on the surface. It is located around the village of Gargellen in Gargellental, a side valley of the Montafon in Vorarlberg on the western edge of the Austrian Central Alps . The Gargellen window was described for the first time in 1843 by the surveyor Alois Richard Schmidt in his geological map of Vorarlberg.

Geological construction

The Gargellen window was created by the fact that the Suggadin brook deepened into the rocks of the Silvretta ceiling along the Landwasser-Gargellen lineaments , a major fault , and cut into the underlying structural unit at its bottom. In the map view it has an area of ​​eight and a half square kilometers and runs for about 6.5 km in north-south direction on both sides of the valley, even if the largest proportion of the area is on the west side. At its widest point, tapering towards the Sankt Antönierjoch, it measures almost three kilometers, the average width is one and a half kilometers.

Only a few 1000 meters west of the Gargellen window lies the western edge of the Silvretta Nappe, which is part of the Eastern Alps. From there to the west, the Penninic is widespread on the surface, rocks from the Eastern Alps are then no longer present, and only a few remains have been spared from erosion in western Switzerland as tectonic cliffs . However, the Gargellen window is still surrounded on all sides by the rocks of the Silvretta ceiling.

All the units of the Gargellen window are heavily rolled out and their sequence of layers is reduced. From bottom to top four are under the crystalline tectonic ceiling units minded :

The Penninic units are overlaid by the gneisses , mica schists , amphibolites and phyllites of the Silvretta ceiling.

Geological importance

In the Gargellen window, under the ceilings of the Eastern Alpine Silvretta ceiling, the deeper underground emerges like a window. Due to tectonic uplift and subsequent erosion , the originally overlying nappes have disappeared in a small area, so that today, in the midst of the gneisses, mica schist, amphibolites and phyllites of the Silvretta nappes, deeper Penninic nappes are exposed. These Penninic nappes originate from the outer area of ​​the European continental plate , which was crossed by the Adriatic plate from the south during the alpine mountain formation , the rocks of which make up today's eastern alpine.

Other windows, the Engadine window located about 20 km to the southeast , the Tauern window and the Rechnitz window located in the far east of the Alps, played a major role in research into the architectural style of the Alps. The Penninic rocks appearing in the windows mentioned show that the rocks that otherwise cover a large area in the Austrian Alps are foreign to the place, i.e. that they were transported from a great distance above their sub-repository. The Gargellen window is a bit out of the way in this row because of its small size and marginal location, but it nevertheless confirms the knowledge gained in the other outcrops.

literature

Individual evidence

  1. ^ Rudolf Oberhauser and Wilfried Rataj: Geological-tectonic overview map of Vorarlberg 1: 200,000 . Vienna 1998.
  2. ↑ Reinhard Schönenberg, Joachim Neugebauer: Introduction to the geology of Europe . 4th edition. Verlag Rombach, Freiburg 1981, ISBN 3-7930-0914-9 , p. 167 ff .

Coordinates: 46 ° 58 '17.6 "  N , 9 ° 55' 5.8"  E