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 __________________________________________________________________________________________ 2.2 Structural frame of the Rax/Schneeberg aquifer system The karstified plateau mountains of Rax and Schneeberg are forming the catchment areas of several springs of the Vienna Water Supply, for example the Kaiserbrunn-, Hölltal, Fronbachand Stixenstein spring. The aquifer is mainly built by Middle to Early Upper Triassic carbonate rocks of shallow water origin – the Gutenstein, Steinalm and Wetterstein limestones and dolomites. Limestones from slope to basinal depositional sites – the Grafensteig limestones – are of some relevance only in the northern Schneeberg area, see stratigraphic scheme Figs. 2 and 3. SCHNEEBERG NAPPE During the alpine tectonics this Wetterstein platform was detached from its basement and from adjacent basinal carbonate rocks and became a tectonically isolated mass of rocks, the Schneeberg Nappe. The Lower Triassic Werfen Formation, which may act as an aquitard or aquiclude, was used as a shear horizon during the nappe movements. Therefore only parts of it remained in the stratigraphic succession of the Schneeberg Nappe, large parts got lost during thrusting. We cannot expect it anymore as a continous layer below the carbonates. The lateral boundaries of the Schneeberg Nappe can be drawn today without any doubt: On the northern side the Triassic rocks of the Schneeberg Nappe are thrusted over Early to Middle Jurassic basinal sediments of the Göller Nappe. The same situation is visible within two tectonic windows, the Ödenhof- and the Hengst-Window. On the western side the tectonic contact shows two different situations. In the northern part the Schneeberg Nappe again superimposes Middle Jurassic basinal sediments of the Göller Nappe. In the southern part Middle Triassic to Carnian rocks of the Schneealpe (Mürzalpen Nappe) are dipping down toward east below the Schneeberg nappe. On its southern side there is an overthrust contact to the Palaeozoic to Lower Triassic shales and siliciclastics of the underlying Werfen Imbricates Zone. The tectonic nature of the contact is proved by the intercalation of several slices of Middle to Upper Triassic rocks of deep shelf and oceanic origin. An additional deformation has affected the southern margin of Schneeberg nappe subsequent to the deposition of the Gosau-Group, resulting in recumbant folds and backthrusting toward south. On its eastern side the Schneeberg nappe is dipping down below transgressive Neogene sediments of the Vienna basin, where it continues in the subsurface (proof by several oil drillings). 21
KATER II Geology of the Rax-Schneeberg-region __________________________________________________________________________________________ Fig. 5: Tectonic sketch Rax-Schneeberg. Fig. 6: Schematic cross-section Rax-Schneeberg. 22
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<strong>KATER</strong> II Geology <strong>of</strong> <strong>the</strong> <strong>Rax</strong>-Schneeberg-region<br />
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Fig. 5: Tec<strong>to</strong>nic sketch <strong>Rax</strong>-Schneeberg.<br />
Fig. 6: Schematic cross-section <strong>Rax</strong>-Schneeberg.<br />
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