Abstract (eng)
Late Triassic Keuper sandstones from the St. Veit Klippenzone of Vienna, predo-minantly medium to coarse-grained in composition, were compared in detail with the dislodged slices of Lower Austria, which occasionally crop out along the base of the Göller nappe. These tectonic slices form intercalations of the terrigenous Keuper within the nappe-pile of the Northern Calcareous Alps, which are predominantly characterized by carbonate sedimentation. Taken together, these occurrences re-present rare, non-metamorphic and poorly investigated Keuper sediments within the Austrian part of the Eastern Alps.
The petrographic analysis identified the rocks as quartz-rich, moderate to poorly sorted litheranites, sublitharenites, feldspathic litharenites and lithic subarkoses. Rock fragments mainly consist of polycrystalline quartz with inclusions of primary mica. According to their mineralogical maturity index (MMI), the samples can be regarded as submature to mature. In some cases, the samples are heavily quartz-cemented. Sporadic calcite cement was also observed. Geochemically, the rocks were classified as sublitharenites, subarkoses and quartz arenites. All samples show SiO2-contents above 90%. The CIA-values revealed that the samples are intermediate to extremely weathered. Provenance analysis after Dickinson and Suszeck (1983) identified a recycled orogen as the most probable source of the clastic material. Results clearly indicate a derivation from igneous (granites), metamorphous (gneisses, schists) and sedimentary (sandstones) rocks. Sedimentary processes could be illustrated by e.g. trace element analysis, which indicates high degrees of sorting and recycling due to long, fluviatile transport. The samples were deposited at a passive continental margin. The heavy mineral assemblage mainly consists of zircon, rutile, tourmaline and strong varying amounts of garnet. Monazite, anatase, baryte/celestine and others only occur occasionally.
In general, the samples show much in common with sandstones whose compositions are derived from stable cratonic sources with overlying sediments and long fluvial transport. By considering the “Nordic-Keuper” concept proclaimed by Behrens (1972) and Köppen and Carter (2000) and the results obtained for this thesis, a long fluvial transport from northern regions, most probably from the Fennoscandian Shield, during Carnian to Norian times must be assumed