Semmering window
Geology refers to the area around the Semmering Pass between Lower Austria and Styria as the Semmering window or Semmering system .
It represents a tectonic window in which older rocks ( crystalline ) of the Austrian Central Alps protrude over younger ones - similar to the Engadine and Tauern window . Its dimensions are about 10 km × 20 km, to which there are also narrow east-west foothills. Other such passages are the interchangeable window or the Rechnitzer window .
However, while the formation of the Penninic of the Western Alps was exposed in the Hohe Tauern and the summit region forms numerous three-thousand-meter peaks , the geological situation on the Semmering is different: it is more or less eroded, but nevertheless mighty nappes of the Lower Eastern Alps , which were created in the course of the Alpine Orogeny have been pushed together considerably.
The ceiling cores of the Semmering window were probably formed in the early stages of the formation of the Alps on the southern edge of the Pennine Ocean . By the violence and spaciousness of tectonic movements the limits of the units run not parallel, as in the Keuper - facies of Semmering window and the main dolomite of the Tauern Window.
According to Siegmund Prey, the building of the lower Eastern Alpine Semmering nappes was created during the Old Alpine Movements, but these shifts may have persisted (weakened) until the Young Alpine orogeny . In the Pennikum, therefore, more and more northerly areas were overwhelmed, whereby the subduction zone , in which the Penninic ocean floor was consumed, must have been active for a long time , despite probable stoppages during the Higher Upper Cretaceous . As a result, the prolonged subduction in this space has resulted in the geological units being compressed into very narrow spaces.
The rocks of the Semmering cover are correspondingly diverse, among which, in addition to granites and gneiss (central, eye, coarse gneiss ), various slates and other crystalline, phyllite , quartzite , albite , meta sediments and greywacke can be found. The (today's) coarse gneiss was partially settled (according to Alfred Pahr) during the Variscan orogeny.
literature
- R. Oberhauser, FK Bauer: The geological structure of Austria . Springer , 1980, ISBN 3-211-81556-2 ( page 73-110, 315 ff. In the Google book search).