Dobra gneiss

The Dobra-gneiss (formerly with today Granodioritgneis of Spitz rock series called for Spitzer gneiss summarized) is a middle- Kamptal common Orthogneis .

Typing

Dobra gneisses are homogeneous, small to coarse-grained biotite gneisses with a leukogranitic, granitic to granodioritic composition. The term was coined by Christof Exner in 1953. The sharply delimited amphibolite and biotite slate intermediate layers, which are typical of the Dobra gneiss and are often switched on, with thicknesses in the decimeter and meter range illustrate the intense folding that can be observed in many areas of the Dobra gneiss and also one causes frequent striations.

The Dobra gneiss is very similar to the Bittescher gneiss of the Moravikums further to the east and was often combined with it in the past. Together with the Colorful Series , however, the Dobra Gneiss forms a tectonic unit of the Moldanubic within the granite and gneiss plateau of the Waldviertel .

Emergence

The mineral composition and the geochemical properties suggest an igneous formation. With an age of 1377  mya , Dobra gneisses represent the oldest exposed rock in Austria in geological terms.

distribution

Dobra gneiss can be found in the area between Artstetten , Ottenschlag , the eponymous Dobra , Allentsteig and to the north of Schwarzenau or to the south of Waidhofen an der Thaya .

literature

• Gerhard Fuchs and Alois Matura (1976): On the geology of the crystalline of the southern Bohemian mass , yearbook of the Federal Geological Institute, Vienna, volume. 119.
• Federal Geological Institute (1980): The Geological Structure of Austria , Springer Vienna, ISBN 978-3-7091-3745-1 , p. 127.