Aarmassiv
The Aar massif is the largest central massif ( mountain massif consisting of geologically old crystalline basement ) in the Swiss Alps . It belongs to the Western Alps .
geology
Along with the Gotthard massif , the Aiguilles Rouges / Arpille massif and the Mont Blanc massif , the Aarmassiv is one of the four central massifs of the Swiss Alps . It is geologically referred to as the Massif Central, because although it was compressed as a crystalline basement , it was not included in the construction of the Helvetic Nappes and is therefore considered to be autochthonous , i.e. locally (hardly shifted in the context of the formation of the Alps). The units of the Helveticum are characterized by the fact that they - unlike large parts of the eastern and southern Alps in particular - were part of the European continent long before the closure of the Tethys Ocean and formed its southern edge, including the offshore shelf area .
The majority of the Aar massif consists of gneiss and granite , as well as crystalline slate and amphibolite . Gneiss, slate and amphibolite emerged from former sedimentary and melt rocks deep in the earth's crust. The granite ( central Aare granite ) penetrated these rocks about 300 million years ago. On its northern flank, the crystalline is covered by unmetamorphic autochthonous to slightly allochthonous sediments from the Jurassic , Cretaceous and Old Tertiary , which are also assigned to the Helvetic. In the course of the increased uplift of the Alps from the Miocene onwards , the sediments deposited on the basement were removed. In some cases, on what is now the northern edge of the Aar massif, there was also slight thrusting of the crystalline northwards over the sedimentary cover layers, for example on the Jungfrau and south of the Eiger .
The geological (tectono-stratigraphic) units of the Aarmassif strike west-southwest-east-northeast, which indicates a main compression in north-northwest-south-southeast direction. Within the crystalline, from north to south, the Lauterbrunner and Innertkirchner crystalline, the old crystalline north of the Aare granite, the central Aare granite (largest granite body in Switzerland with 500 km² outcrop area in the Grimsel-Göscheneralp-Reuss valley) and the southern gneiss zone (high proportion from eye gneiss).
geography
The Aar massif extends geologically in a west-east direction north of the alpine long valley from about Leukerbad to Tödi . In the area from Tödi and Cavistrau to about Brigels , the Aar massif only forms the base of the mountains, the peaks of which consist of sediments. Further north and east, the Aar massif is only exposed in extremely deep valleys, for example on the Limmerensee and between Gigerwald and Vättis (Vättner window ) . To the southwest of Leukerbad and Leuk , the Aarmassiv dips beneath the Pennine nappes of the Valais Alps .
It is connected underground with the massifs of Mont Blanc and the Aiguilles Rouges , which are already emerging again west of Sion on the south side of the Grand Chavalard .
Major peaks
Aare granite: Bietschhorn , Nesthorn , Dammastock , Oberalpstock .
Crystalline shell of the Aare granite: Aletschhorn , Jungfrau , Mönch , Finsteraarhorn , Schreckhorn , Sustenhorn , Bristen , Düssi .
Mesozoic sediment cover ("Autochthon"): Balmhorn , Blümlisalp , Eiger , Wetterhorn , Titlis , Windgällen, Clariden , Tödi , Hausstock .
literature
- Toni P. Labhart: Geology of Switzerland . Ott Verlag, Thun 1992, ISBN 3-7225-6298-8 .
- Albert Heim: The geology of the high Alps between Reuss and Rhine. Bern 1891.