Helvetic system

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Geological sketch of the Alps. The Helvetic (green) is particularly common in the western half of the Alps

The Helvetic System , also known as the Helvetic for short and Dauphiné in the French Alpine region , is, together with the Ultra-Helvetic, one of the major geological cover systems in the Alps, alongside the Southern and Eastern Alps and the Pennine . The ceilings of the Helveticum consist mainly of Cretaceous and ancient Tertiary sediment deposits that are folded several times . Upper Jurassic and older rocks, which in the crystalline massifs of Switzerland and France at least extend into the Carboniferous , also contribute to the Helvetic stratification .

The Helvetikum is named after Switzerland (lat. Helvetia ), where this system was first described. Many of the Helveticum type localities are in Switzerland.

Deposition and formation

The rocks of the Helveticum were originally deposited on the European shelf . Depending on the original location, the thickness of the layers of the Helveticum increases from north to south (in the Western Alps from west to east): near the original coast, the deposits are thin, often patchy and influenced by the land; The south is characterized by mighty limestone series . The layers of the Ultrahelvetic originate from the extreme southern shelf edge of Europe adjoining the Helvetic and mark the transition into the Pennine Ocean , which represents the western edge of the Tethys .

During the alpine mountain formation , the Helvetic rocks including some crystalline massifs were sheared off their sub-beds and pushed northward onto the European continent as the northernmost part of the alpine nappes . The layers originally deposited horizontally were folded and disrupted in a complicated way .

Occurrence

In France, the Helvetikum (also called Dauphiné here ) forms the western half of the Alps between Cannes via Grenoble to Mont Blanc . The highest peaks are the gneisses and granites of the crystalline massifs of the Pelvoux , the Belledonne , the Montblanc and the Aiguilles Rouges . In front of them to the west are the Helvetic limestone massifs of the Provencal Prealps , the Dauphiné Alps and the Savoy Alps .

In Switzerland, the Helvetic and its crystalline parts form the northern half of the Alps. Apart from the gneisses and granites of the Aar and Gotthard massifs, the siliceous limestone is the main summit builder in the Bernese and Glarus Alps upstream from them due to its resistance to weathering . The Helvetikum in the area of ​​the Säntis and the Churfirsten is extremely open .

The systems of Eastern Switzerland stretch over Vorarlberg ( Bregenz Forest ) to the Allgäu (area around Oberstdorf and the Hohen Ifen ).

In the rest of the Alps, the Helvetic is hardly open, as it is mostly pushed over by the flysch zone ( rhenodanubian flysch ) above it . To the north of Salzburg the blanket comes to light again, from there it stretches in front of the Northern Limestone Alps as a frequently interrupted band of small-scale tectonic scales within the rhenodanubian flysch zone to the western edge of the Vienna Basin . The rocks of the Helveticum are not particularly prominent here in the area.

Tectonics and metamorphosis

Profile through the Helvetic Republic on the northern slope of the Eastern Swiss Alps

The Helvetikum shows a complicated ceiling structure. A rough distinction is made between:

  • ultrahelvetian blankets and ultrahelvetian flysch
  • Upper or South Helvetic blankets
  • Lower or North Helvetic blankets

Some geologists also consider parts of the Tauern Window to be Helvetic.

stratigraphy

Eastern Switzerland / Vorarlberg / Allgäu

The main shift members from Eastern Switzerland to the Allgäu are from old ( lying ) to young ( hanging ) as follows:

literature

  • MP Gwinner: Geology of the Alps . 2nd Edition. Schweizerbart, Stuttgart 1978, ISBN 3-510-65315-7 .
  • R. Oberhauser, FK Bauer: The geological structure of Austria . Springer , 1980, ISBN 3-211-81556-2 ( page 189 ff. In the Google book search).
  • Hans Heierli: Geological hiking guide Switzerland. Part 1: The geological basics . 2nd Edition. Ott Verlag, Thun 1983, ISBN 3-7225-6282-1 .
  • Reinhard Schönenberg, Joachim Neugebauer: Introduction to the geology of Europe . 4th edition. Verlag Rombach, Freiburg 1981, ISBN 3-7930-0914-9 , p. 174 f., 183 f .

Individual evidence

  1. ↑ Bayerisches Geologisches Landesamt (Ed.): Explanations for the geological map of Bavaria 1: 500,000 , 3rd edition, GLA, Munich 1981.
  2. ↑ In Upper Bavaria, however, a prominent climbing garden near Bad Heilbrunn opens up well. Frank Trixler: Enzenau quarry . In: Fossilien 6, No. 1, 1989, pp. 8-9. ISSN  0175-5021
  3. ^ O. Adrian Pfiffner: Geologie der Alpen , Haupt-Verlag, Bern 2009, ISBN 978-3-8252-8416-9 , page 47.