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

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KATER II Geology of the Rax-Schneeberg-region __________________________________________________________________________________________ 1 STRATIGRAPHY The Northern Calcareous Alps (NCA) – as a prominent part of the Eastern Alps – extend for about 500 kilometers from the Rhine valley in the west to Vienna in the east, forming a 20 to 50 kilometer wide mountain belt. In the western and middle part the highest peaks reach altitudes of up to 3.000 meters and are locally glaciated, in the eastern part elevations are up to 2.000 meters (Rax, Schneeberg). At their eastern end the NCA are bounded by the Vienna Basin, which subsided during Neogene times. In the basement of the Vienna Basin, however, the NCA continue into equivalent units of the Western Carpathians even if the details are still in discussion. The Grauwacken Zone, consisting mainly of Ordovician to Carboniferous Metasediments, is the basement of the NCA. The transgressive sedimentary sequence of the NCA begins in the Permian and extends locally into the Paleogene (Gosau Group). The Triassic carbonates are the most prevailing rocks. They are forming extended karstified landscapes, the catchment areas of several drinking water supply systems – the most importend one is the Vienna water supply. Due to the intense nappe tectonic during the Alpine orogenesis the originally succession of sedimentary rocks has been dissected into several nappes with different stratigraphic content. Therefore the legend of the map as well as the explanatory notes are grouping the formations according to the main tectonic units and then according to their sedimentary age, beginning with the oldest one. Overviews as well as detailed data and further literature to this topic are given by BÖHM 1992, FAUPL & WAGREICH 1996, FLÜGEL 1981, LEIN 1987, LOBITZER, MANDL, MAZZULLO & MELLO 1990, MANDL 2000, MANDL & ONDREJICKOVA 1993, NEUBAUER et al. 1994, SCHLAGINTWEIT & EBLI 1999, TOLLMANN 1976, 1985, 1986, WAGREICH & FAUPL 1994, ZANKL 1971. A schematic representation of the Triassic sedimentary sequences is shown in Figs. 2 and 3. 1.1 Noric-Tyrolic Nappe System Greywacke Zone (95) – (91) The palaeozoic metasediments of the Greywacke Zone are separated into three nappes, two of them can be found in the project area: # the Silbersberg Nappe contains remnants of a crystalline basement („Vöstenhof- Crystalline”) and transgreding siliciclastics of the Silbersberg-Group (95). # the Noric Nappe is built by phyllits and greenschists (94), Ordovician volcanic rocks of the “Blasseneck Porphyroid” (93), Silurian sandy grey shale “Radschiefer” (92) with lydites and Devonian carbonate rocks (91). Werfen Imbricates Zone (90) – (85) The sedimentary sequence of the NCA starts in the Permian with continental red beds, conglomerates, sandstones and shales of the Prebichl Formation (90, 89), transgressing onto Lower Palaeozoic rocks of the Greywacke Zone. The Permian age is assumes due to local intercalations of acid tuffs and pebbles of quartz porphyry, which are widespread in the 7
KATER II Geology of the Rax-Schneeberg-region __________________________________________________________________________________________ European Permian. Locally occurs a body of Quartz porphyry (88), tectonically embedded in Werfen shales. The Lower Triassic is characterized by uniform shallow shelf siliciclastics of the Werfen Formation (87), containing limestone beds (86) in its uppermost part with a poor fauna including Scythian ammonoids. Tectonized Anisian dolomites form elongated bodies of Rauwacke (85) within and on top of the siliciclastics. 1.2 Meliaticum (84) Along one of the main thrust planes we find two Klippen of sedimentary rocks of a deep water origin, unknown elsewhere in the NKA, but well known as Meliaticum in the Western Carpathians. These rocks represent the transition from the Triassic Hallstatt carbonatic depositional realm into oceanic conditions with radiolarites. We have hints on the existence of such an oceanic realm only in form of olistolites of Ladinian red radiolarite in the Middle Jurassic silicious shales of Florianikogel Formation (84) - see MANDL & ONDREJICKOVA 1991, 1993, KOZUR & MOSTLER 1992. 1.3 Juvavic Nappe System Within a distinct zone of tectonic disturbance several partly recrystallized carbonate rocks occure, which have been assigned in older maps to the Carnian Opponitz Formation. No fossils have been found until now; lithology and discordant position do not confirm this opinion. Therefore these rocks are summarized here as carbonates of unknown stratigraphic origin (83). PERMIAN – LOWER TRIASSIC (83) – (79) A marine facies of Permian sediments is the so called Haselgebirge (82), a sandstone-clayevaporite association, containing gypsum and salt. This facies is frequent in the Juvavic units, exposed for example in the Pfenningbach gypsum open pit mine east of village Puchberg. The Upper Permian age is proved paleontologically by pollen/spores at several localities in the NCA and confirmed by sulfur isotopes. The Lower Triassic is represented again by siliciclastics of Werfen Formation (81, 80), accompanied by Anisian Rauwacke (79) - see also above. MIDDLE TRIASSIC TO LOWER CARNIAN (78) – (61) Beginning with the Middle Triassic carbonate sedimentation became dominant. The dark Gutenstein Limestone (76) and Dolomite (77) is present in most of the NCA nappes. A local variety is a multicolored Flaser Limestone (78). The Gutenstein carbonates can be laterally replaced in the upper part by light dasycladacean bearing carbonates, the Steinalm Limestone/Dolomite (75, 74). During the Middle Anisian a rapid deepening and contemporary block faulting of the so called Reifling Event has caused a sea floor relief, responsible for the following differentiation into shallow carbonate platforms (Wetterstein Formation and lateral slope sediments) and 8
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Explanatory notes to the digital geological map of the Rax ... - KATER

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