Explanatory notes to the digital geological map of the Rax ... - KATER

KATER II Geology of the Rax-Schneeberg-region
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INTERNAL THRUSTS
An east-west directed compression has caused a synkline west of Heukuppe, which contains
the tectonic outlier of Hohe Gupf. Folding and westward directed thrusting in the adjacent
Altenberg valley is also ascribed to this deformation act.
Much more prominent for the hydrogeology of the Schneeberg-Nappe is a west directed
internal thrust (Markgraben thrust) in the western Gahns plateau – see also cross section 4.
The southern margin of the Schneeberg-Nappe has been affected by backthrusting after the
deposition of the Upper Cretaceous to Palaeocene Gosau-Group. This Gahnsleiten
Imbricates contain slices of Wetterstein reef and slope deposits with transgressively
connected Gosau formations, as well as lenticular bodies of Wetterstein limestone and
Werfen shales. The main part of the Schneeberg-Nappe is following above, beginning with
the Anisian Gutenstein Formation.
FAULT SYSTEMS
The Krummbach fault system seems to be a strike slip fault (local flower structures in
Krummbach valley and at Brettschacher) combined with a vertical offset: the Schneeberg
side has been uplifted, exposing older rocks and the underlying Göller Nappe in tectonic
windows, while the Rax side exposes the youngest part of the Wetterstein Limestone near to
the Schwarza valley floor.
A younger fault system shows extensional character:
The Weichtal normal fault has caused a displacement of about 600 m between
Hochschneeberg (hangingwall) and Kuhschneeberg (footwall). The faults in the Großes
Höllental seem to be a direct continuation of the Weichtal fault, but they exhibit quite opposite
movements: the western block (Heukuppe-Klobenwand) has been relatively uplifted about
200 m compared with the eastern block (Preinerwand-Grünschacher).
The Breitensohl normal fault forms the western margin of the tectonic window of Hoher
Hengst, displaces the Krummbach fault some hundred meters and continues into the eastern
Gahns massive. The normal displacement east of Hengst is 800 m as a minimum and
degrees toward south to about 400 m.
The NNE-SSW directed fault system at Bodenwiese has squeezed up Lower Triassic Werfen
shales probably by strike slip movements.
MÜRZALPEN NAPPE
The northern margin of the Mürzalpen-Nappe is often affected by younger faults or covered
by tectonic outliers. Its eastern end is dipping down under the Schneeberg-Nappe and at its
southern margin it is thrusted over rocks of the Werfen Imbricates Zone.
The Mürzalpen-Nappe has only minor influence on the Rax-Schneeberg-aquifere, therefore it
is not treated here in detail.
GÖLLER NAPPE
The Göller-Nappe consists here mainly of Hauptdolomite, which is gradually replaced toward
the south by lagoonal Dachstein limestone. Sandy shales of the Carnian Raibl-Group act as
a shear horizon during internal thrusting.
The sedimentary succession continues into Jurassic red limestones and marly/cherty basinal
sediments of Allgäu Formation and locally into red radiolarite.
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