Systematik, Biostratigraphie und Paläoökologie der Ostracoden des Badenium in Österreich unter besonderer Berücksichtigung der von Reuss (1850) beschriebenen Arten

The results of the project "Systematics, biostratigraphy and paleoecology of the ostracodes from the Badenian (Middle Miocene) in Austria with special emphasis on the species described by REUSS (1850)" show clearly, that the established ostracod biozonations at best have local ecostratigraphic significance according to the strong ecological dependence of the ostracod occurrences and the slight state of knowledge concerning the distribution of the single species. For the time being a reliable biostratigraphic classification of rock samples is possible only in combination with other groups of organisms (e.g. Foraminifera). In the present project fossil ostracods (small crustaceans with a size of around 1mm) of the Middle Miocene (Badenian, 16,4-13 Ma) of Austria were investigated micropaleontologically. The fossils come from marly interlayers of the so-called "Leithakalk" and clayey-sandy sediments (e.g. "Badener Tegel") which represent marginal and basinal deposits of the Paratethys Sea which at that time also was expanded over parts of today`s Austria. The investigated samples on the one hand come from collection stocks such as the ostracod collection of A. E. REUSS at the Museum of Natural History in Vienna and on the other hand were taken during fieldwork made in the scope of the project. The areas of the Molasse Basin of Lower Austria, the Vienna Basin (incl. neighbouring Basins), the Styrian Basin and the Carinthian Lavanttal, which geographically cover the area of distribution of the Badenian, have been taken into account. Before the samples were analysed scientifically they have been washed fractionally with sieves, dried and the ostracodes were picked under the microscope. Subsequently the sorting and determination of the species followed. Approximately 100 Badenian species could be distinguished. Most of the species were studied with the scanning electron microscope for fine structures and were photographed and described for the purpose of documentation. The systematic-taxonomic revision of the species described by REUSS in the year 1850 allows to compare the prevailing occurrences under the momentary species names with the present illustrations and new descriptions and to refine the paleobiogeographical and stratigraphical distribution. Besides the systematic and paleoecologic investigation the main aim of the project was the biostratigraphic interpretation of the ostracods. Because the sampled localities were biostratigraphically classified by foraminifers (testacean protozoans), it could be analysed which stratigraphical distribution the single species exhibit within the Badenian. The bulk of the recorded species show a wider stratigraphical range within Austria than has been known so far and partly are distributed within the whole Badenian. It is stated that the existing 4 ostracode biozones for the division of the Badenian in the Central Paratethys only partly can be applied to the Austrian occurrences because hitherto only few index fossils could be identified and these are extremely rare. The reason for this is the strong ecological dependence of the occurrence of the ostracod species. The results of this project are not only important for the local geological mapping program, the interpretation of oil- and water drillings and the stratigraphical correlation of different depositional areas, but have also european if not worldwide significance as several of the species described by REUSS have been documented outside Europe.