Hohe Tauern window

Tauern window is the geological name of a region in the Central Alps in Austria, in the window-like Pennine ceiling and possibly Helvetic ceiling, framed by rocks of the Austroalpine, are open-minded. The tectonically deepest parts of the Tauern window, the central gneiss cores surrounded by rocks of the so-called Schieferhülle. Of similar origin and geological position of the smaller, further west, Engadine window and the Gargellenfenster in Vorarlberg and the Rechnitz window at the east end of the Alps.

Location

The Tauern Window is located in the Austrian provinces of Tyrol, Salzburg and Carinthia between the Brenner Pass in the west and the line Schladming - Mauterndorf in the east, his most southwestern corner is in South Tyrol and thus already in Italy. It has from the southwest corner south of the Brenner to Schladming in the northeast a length of about 176 km and between Mittersill and Matrei a north- south extension of about 30 km. At its widest point between Sankt Johann im Pongau and Spittal, it measures almost 54 km. Its rocks essentially build on the Zillertal Alps and the eponymous Hohe Tauern.

Formation

In simplified formed the base of the Lower Cretaceous to existing in the period Malm former Piedmont Ocean, the parent rocks of the disrupted today in the Tauern Window rocks.

In the course of the Alps Education joined the ocean, and its cover rocks were pushed over like in the Cretaceous and Tertiary period of the rock formations of the Austroalpine and in this way ( geological) relatively quickly drowned in the depth. From the metamorphic ( " crystalline " ) rocks in the Tauern Window, a former cover thickness of more than 10 km can be derived. The rocks were subject to several metamorphoses, changing their mineral constituents accordingly and became the now upcoming crystalline rocks. For example, an early, retrograde eklogitfazielle metamorphosis ( at pressures of 1.9 to 2.2 GPa and temperatures of 600 to 630 ° C) of a subsequent blauschieferfaziellen metamorphosis ( with pressures from 0.9 to 1.0 GPa and at temperatures distinguish 400-450 ° C); Metamorphoses both belong to the type of high-pressure low-temperature (HP / LT), which is characteristic of subduction zones. After the sinking was a geologically equally rapid recovery uplift of the rocks.

Towards the end of the Oligocene were first rocks of the Tauern Window to a greater extent at the free surface, as can be read off in the sediments of the Alpine Molasse on the emergence of characteristic heavy minerals. The lifting of the Alps - and the Tauern Window - now takes on even more. The while active processes are weathering and erosion, so that the Tauern window is slowly increased to the same extent over time, as the formerly overlying rocks of the Austroalpine be removed.

The Tauern Window as penninisch - Helvetic double window

Some geologists the Tauern window is described as a double window, appear in the Pennine not only, but also Helvetic units. Thus, the lower shale shell and the central gneisses are assigned to the Helvetic system. Reason for this assumption are studies which have shown that the sequence of layers in the Tauern Window partially consistent with the European continental margin in Helvetic facies. This allows the malmischen Hochstegenkalke with the Quintner limestones in the Helvetic area compare.

For the first time of a Helvetic facies in the Tauern Window Otto Thiele said in 1970. A tectonic assignment to the Helvetic area and thus the definition of the Tauern Window as penninisch - Helvetic double windows called 1986 Bernd Lammerer.

Is also found in more recent publications that view. Thus, the research group led by Schmid believes that the Lower Schieferhülle the Tauern Window as well as the central gneiss belongs to the Sub - Penninic containing tectonically highly deformed remnants of the European continental margin, ie not taken from the actual Penninic Ocean. Likewise, Othmar Adrian Pfiffner is in its 2009 published geology of the Alps for an assignment of certain portions of the layer sequence of the Tauern Window to the Helvetic.

Scientific Importance

The existence of the Tauern Window was in the geological Erfoschungsgeschichte the Alps an important milestone for the understanding of mountain building. Early mapping work was undertaken in 1853 by Marko Vincenç Lipold and his assistant Dionys Stur and Carl Ferdinand Peters, which were continued by other geologists in the years of the second half of the 19th century.

In the subsequent work of the first half of the 20th century the Alps have been extensively studied geology, and still valid today outline the major units of the Südalpins, Austroalpine, Penninikums and Helvetic was erected. The Tauern Window was attributed to the Penninic and explores its geological structure in essential. Many research on the geochemistry and isotope geology appeared from the beginning of the 1970s, and since about 1980 the processes of mountain building alpidischen were interpreted plattentektonisch.

Pierre -Marie had Termier 1903, the theory argued that the Western Alps in eastern Switzerland disappear beneath the Eastern Alps and träten to light again in the Hohe Tauern in a tectonic window. This statement triggered a decades-long dispute between geologists Fixisten and mobile home. Today it is clear that the theory of Termier corresponds to the truth: the rocks of the Austroalpine have been pushed away at least 150 km over the entire area of the Tauern Window.