Explanatory notes to the digital geological map of the Rax ... - KATER
Explanatory notes to the digital geological map of the Rax ... - KATER Explanatory notes to the digital geological map of the Rax ... - KATER
KATER II Geology of the Rax-Schneeberg-region __________________________________________________________________________________________ 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. 23
KATER II Geology of the Rax-Schneeberg-region __________________________________________________________________________________________ Die Göller-Nappe dips down toward south under the Schneeberg-Nappe, forming a wide west-east striking syncline. The southern flank of this syncline is visible in the Lahngraben-, Hengst- and Ödenhof-windows. Here it is cut off by the Krummbach fault system. The continuation of the Göller-Nappe in the south of these faults cannot be proven directly. It is probable due to the occurrence of Wettersteindolomite in the surrounding of Hinternaßwald, which one must be part of the Göller-Nappe in such a southern position. The former mentioned syncline is dissected by the Weichtal normal fault into an eastern and a western part. In the eastern part of the syncline the Jurassic Allgäu Formation and the Werfen Formation of Schneeberg-Nappe are forming a thick aquiclude layer below the carbonates of Hochschneeberg. In the western part of the syncline the Allgäu Formation is gradually replaced by red limestones and radiolarite of minor thickness. Also the Werfen formation may wedge out locally. Therefore no continuous aquiclude can be expected in the subsurface of the western Kuhschneeberg and Fegenberg. WERFEN IMBRICATES ZONE As mentioned above the Permo-Triassic siliciclastic rocks of this zone exhibit a transgressive contact to the Early Palaeozoic rocks of the Grauwacken Zone. The tectonic contact to the Schneeberg-Nappe is proven by intercalated Juvavic slices and Meliata Klippen. Additional internal thrusting is probable due to incorporated younger rauwacke and ?Permian quartzporphyry. This zone is forming a thick aquiclude layer below the carbonates in the southern part of the Schneeberg-Nappe. 24
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<strong>KATER</strong> II Geology <strong>of</strong> <strong>the</strong> <strong>Rax</strong>-Schneeberg-region<br />
__________________________________________________________________________________________<br />
Die Göller-Nappe dips down <strong>to</strong>ward south under <strong>the</strong> Schneeberg-Nappe, forming a wide<br />
west-east striking syncline. The sou<strong>the</strong>rn flank <strong>of</strong> this syncline is visible in <strong>the</strong> Lahngraben-,<br />
Hengst- and Ödenh<strong>of</strong>-windows. Here it is cut <strong>of</strong>f by <strong>the</strong> Krummbach fault system. The<br />
continuation <strong>of</strong> <strong>the</strong> Göller-Nappe in <strong>the</strong> south <strong>of</strong> <strong>the</strong>se faults cannot be proven directly. It is<br />
probable due <strong>to</strong> <strong>the</strong> occurrence <strong>of</strong> Wettersteindolomite in <strong>the</strong> surrounding <strong>of</strong> Hinternaßwald,<br />
which one must be part <strong>of</strong> <strong>the</strong> Göller-Nappe in such a sou<strong>the</strong>rn position.<br />
The former mentioned syncline is dissected by <strong>the</strong> Weichtal normal fault in<strong>to</strong> an eastern and<br />
a western part. In <strong>the</strong> eastern part <strong>of</strong> <strong>the</strong> syncline <strong>the</strong> Jurassic Allgäu Formation and <strong>the</strong><br />
Werfen Formation <strong>of</strong> Schneeberg-Nappe are forming a thick aquiclude layer below <strong>the</strong><br />
carbonates <strong>of</strong> Hochschneeberg. In <strong>the</strong> western part <strong>of</strong> <strong>the</strong> syncline <strong>the</strong> Allgäu Formation is<br />
gradually replaced by red limes<strong>to</strong>nes and radiolarite <strong>of</strong> minor thickness. Also <strong>the</strong> Werfen<br />
formation may wedge out locally. Therefore no continuous aquiclude can be expected in <strong>the</strong><br />
subsurface <strong>of</strong> <strong>the</strong> western Kuhschneeberg and Fegenberg.<br />
WERFEN IMBRICATES ZONE<br />
As mentioned above <strong>the</strong> Permo-Triassic siliciclastic rocks <strong>of</strong> this zone exhibit a transgressive<br />
contact <strong>to</strong> <strong>the</strong> Early Palaeozoic rocks <strong>of</strong> <strong>the</strong> Grauwacken Zone. The tec<strong>to</strong>nic contact <strong>to</strong> <strong>the</strong><br />
Schneeberg-Nappe is proven by intercalated Juvavic slices and Meliata Klippen. Additional<br />
internal thrusting is probable due <strong>to</strong> incorporated younger rauwacke and ?Permian<br />
quartzporphyry. This zone is forming a thick aquiclude layer below <strong>the</strong> carbonates in <strong>the</strong><br />
sou<strong>the</strong>rn part <strong>of</strong> <strong>the</strong> Schneeberg-Nappe.<br />
24
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