Foreland molasses

from Wikipedia, the free encyclopedia

In geology, an arched area of ​​more or less flat molasse sediments on the northern edge of the Alps is referred to as foreland molasses . South of the foreland molasse are the steep and scaly rocks of the subalpine molasse . Both units belong to the Molasse Basin (see there for details of the formation of today's surface, layer sequence and tectonics ).

structure

The outermost southern edge of the foreland molasse was captured and bent up when the subalpine molasses were attached to the nappes of the Alps ; this area is called erect molasses . Under the Alps, the existence of a part of the foreland molasse that was crossed by the Alps has been proven, which extends a few tens of kilometers to the south under the Alpine body. This part is referred to as the Molasse that has been driven over, but its assignment to the foreland molasses is problematic due to the expected scaling and tectonic deformation.

Occurrence

The foreland molasse lies in front of the entire northern Alpine front. With a length of about 1,000 km, it extends over parts of France , Switzerland , Germany and Austria . At its western end on Lake Geneva , it is about 20 km wide, extends in an easterly direction far to the north and reaches its greatest width of almost 130 km in the Bavarian Alpine foothills . Further east, the width decreases at the height of Amstetten to about 10 km; from there it stretches as a narrow strip to about St. Pölten , then widens - pivoting in a northeasterly direction - to a width of about 40 km, and merges north of the Danube into the Carpathian pre-depth .

Emergence

The foreland molasse was formed by filling in an arm of the sea, which arose when the Alps were formed on their northern edge as a result of the load of the mountain body on the European crust . This arm of the sea was filled with the debris removed from the rising Alpine body. The lowering of the crust kept pace with the filling of the basin, so that finally up to 5,000 m of sedimentary rocks could be deposited. The southern edge of this molasse basin was crossed by the pile of blankets from the Alps and partially attached to the mountain body (subalpine molasse). The foreland molasse was largely spared from these processes and suffered at most a fractional tectonic deformation.

swell

  1. ↑ Explanations of the Geological Map of Bavaria 1: 500000, p. 268
  2. ↑ Explanations of the Geological Map of Bavaria 1: 500000, p. 141
  3. ↑ Explanations of the Geological Map of Bavaria 1: 500000, p. 148

Literature and maps

  • Geological map of Switzerland 1: 5000 000 Swiss Geological Commission, 1980
  • Geological hiking guide Switzerland. Part 1: The geological basics . Hans Heierli, Ott Verlag, 173 pp., 2nd edition, Thun 1983. ISBN 3-7225-6282-1
  • Geological map of Bavaria 1: 500000 with explanations . Bavarian Geological State Office, Munich, 4th edition 1996.
  • Geological overview map of the Republic of Austria with tectonic breakdown 1: 1,000,000 Geological Federal Agency Vienna, revised reprint, Verlag Frytag, Berndt and Artaria, Vienna 1986.

Web links