Molasse basin
From Wikipedia, the free encyclopedia
| Geology of the Alps |
|---|
 |
| Tectonic subdivision |
| Penninic nappes |
| Austroalpine nappes |
| Southern Alps |
| Formations & rocks |
| Geological structures |
|
Aarmassif | Dent Blanche klippe | Engadine window | Flysch zone | Giudicárie line | Greywacke zone | Hohe Tauern window | Molasse basin | Penninic thrustfront | Periadriatic Seam | Ivrea zone | Lepontin dome | Rechnitz window | Rhône-Simplon line | Sesia unit |
| Paleogeografic terminology |
| Briançonnais microcontinent |
| Piemont-Liguria Ocean |
| Apulian or Adriatic plate |
In geology, a molasse basin is the stage of a developing foreland basin, in which molasse is deposited. The term is used for all localities, but this type of basin was first studied in the Swiss and Bavarian foreland of the Alps, therefore that particular basin is called the Molasse basin.
"The" Molasse basin was formed during the early Tertiary period as a result of crustal thickening with the rising of the Alps. The basin filled with the products of erosion and weathering in the new mountain range, sand, gravel and boulders deposited as fans of sandstones and conglomerates. The base of the basin was formed by pre-orogenic (Mesozoic) sedimentary rocks. When the Alps rose further, a decollement horizon developed at the base of the Mesozoic rocks (in Triassic evaporites), along which thrusting to the north took place, forming the Jura mountains to the northwest. The Swiss part of the Molasse basin was now located in between the Alps and Jura, as a large piggy-back basin. In the Eastern Alps an external mountain range never developed, the Molasse basin of the Eastern Alps is therefore simpler in its structure. Due to the continued thrusting, foreland basin extension was soon compensated by uplift. The molasse is now at 200 to 300 meters above sea level.
Today the position of the basin accounts for the relatively flat landscape in the Swiss Plateau and the South Bavarian plain.
