Lithologies
The Austroalpine nappes are fragments of the former continental shelf and continental slope of the Apulian or Adriatic plate. These fragments contain rocks from the continental basement as well as from sedimentary rocks deposited in these environments.
The basement rocks have experienced metamorphism related to their original depth in the Earth's crust, but in the Austroalpine nappes Alpine metamorphism (i.e. metamorphism related to the formation of the Alps) is fairly low grade to non-existent. The basement rocks can be greenschist facies to amphibolite facies, depending on their original depth. They are Paleozoic schists and (para-)gneisses intruded by granites of Variscan and Tertiary age.
On top of this basement rock, Permian and Mesozoic sedimentary and volcanic rocks were deposited. Shallow marine limestones are abundant, these limestones now form the mountain chains of the northern part of the Eastern Alps, which are therefore together called the Northern Calcareous Alps. Sometimes, the limestone has been turned into dolomite, as in the Austrian region Salzkammergut and the German region Allgäu.
A special unit is the greywacke zone, a band of Paleozoic metamorphosed sedimentary rocks that forms an east-west band through the Austrian Alps. The greywacke zone crops out between the Mesozoic rocks of the Northern Calcareous Alps and the Austroalpine and Penninic basement rocks of the Central Eastern Alps. Stratigraphically, the greywacke zone can be up to 2 kilometres (1.2 mi) thick.
All of these lithologies were folded and thrusted, so that the basement rock can be found on top of the sediments and vice versa.
Read more about this topic: Austroalpine Nappes