The Aarmassif or Aaremassif (German: Aarmassiv) is the easternmost geology massif in the Swiss Alps.
Name
The massif is named after the
Aar, a river that has its source in the Aarmassif.
Geography
The Aarmassif
outcrop in the eastern part of the
Bernese Alps and the
Lepontine Alps, roughly from
Leukerbad in the west to the Tödi in the east. Further east the massif only appears in small windows like the
Vättner window between Gigerwald and Vättis in Sankt Gallen and at the
Limmerensee in the same canton.
The
Grimsel Pass crosses it.
Tectonics and lithology
The Aarmassif is part of the
Helvetic zone of the Alps, which consists of material originally from the European
tectonic plate. The Aarmassif has
Lithology common for
Paleozoic basement rocks all over Europe, deformed and
metamorphism during the
Variscan orogeny. Younger
Mesozoic were
erosion from this basement as a
thrust fault brought the basement to the surface in the
Alpine orogeny. Other places, where the European basement crops out in the Helvetic zone, are the mountain chains of the Massif des Écrins and of
Mont Blanc in the
France and
Italy Alps.
The lithologies of the basement rocks are mainly , and . These were in some places intruded by Permian after the Variscan orogeny, called Aare granite. During a late phase in the Alpine orogeny in the Tertiary period the Aarmassif was tectonic uplift in the form of a large elongated dome structure. The overlying limestones of the Helvetic nappes now have a very high dip angle, forming a ridge that appears at the Eiger and south of the Jungfrau mountain.
See also
