Extracting palaeoecological and palaeoclimatic data from dispersed fruits and seeds (diaspores) in Miocene terrestrial ecosystems of eastern Austria.

Research project P 13742 Reconstructin Miocene ecosystems with diaspores in Austria David K. FERGUSON 28.06.1999 During Miocene times the evolution and uplift of the Alpine orogenic belt created new palaeogeographic and topographic conditions. As a result of the dissemination of fruits and seeds (diaspores), the vacant spaces became colonized by plants. The Molasse foreland basin, situated N to the developing Alpine orogene and in the eastern pan, S of the Bohemian Massif accumulated clastic sediments and plant detritus from the newly exposed terrestrial areas. Molasse sediments are widespread in the northern and northeastern parts of Austria. The intensive extensional movements of the alpine nappes produced numerous fault systems, which resulted in subsidence and the creation of intramontane basins in the southeastern part of Austria. The sediments, which subsequently filled these basins, are plant-bearing. Different time slices from the earliest Miocene (Eggenburgian) up to the late Miocene (Pannonian) are chosen in order to study the changes in the palaeo-ecosystems in these two tectonically-induced depositonal areas. Previous geological and palaeobotanical research as well as the preliminary investigation of test samples are promising. A more complete picture will be obtained by combining the results with those of the leaf and palynology projects. Reference to the geological and palaeozoological projects should help to evaluate the causes of the changes in the palaeo-ecosystems. The main aims of the present project are: * Identification of the diaspores from the various depositonal areas (Molasse Basin; intramontane basins: Fohnsdorf Basin; Pannonian Basin System: Styrian Neogene Basin, Pannonian Basin s.str.) and time slices (Egerian/ Eggenburgian, Eggenburgian/ Ottnangian, Karpatian/ Badenian, Sarmatian, Pannonian). * Palaeoecological characterization of the diaspore spectra and the reconstruction of characteristic plant communities in the zonal and azonal vegetation from the different areas and time slices. * Investigations of the potential causes (e.g. regional edaphic conditions) of the differences and similarities in the diaspore spectra from similar habitats between the Molasse and intramontane basins. * Combination of the data on diaspores, palynomorphs and leaves in order to obtain a more complete picture of the various vegetational patterns in the different areas and time slices. * Palaeoecological analyses of all plant and animal remains in relation to the sedimentological and geodynamic conditions. * Evaluating reliable taxa. for a regional biostratigraphy and comparing the results with biostratigraphic models in South Germany and Lusatia.

Plant assemblages were collected from a number of Miocene localities in eastern Austria. These were identified and interpreted from a palaeoecological, palaeoclimatic and to some extent from a biostratigraphic point of view. The assemblages differ in their systematic affinities and their degree of diversity. Numerous fruits and seeds had never before been recorded from the Austrian Neogene. The carpofloras from the Upper Miocene sediments in the former lignite mining area of Hausruck (Upper Austrian Molasse Zone) proved to be particularly diverse and well-preserved. With over 80 species, it is possible to reconstruct the different environments and plant communities: large lakes with water lilies, water chestnuts, pondweeds, water-milfoils, broad littoral belts with numerous sedges, swamp forests with the swamp cypress, as well as riparian woody vegetation. The hinterland elements, i.e. those plants which are not controlled by the watertable, only occur sporadically, which indicates that they were growing at some distance from the site of deposition. A comparison of all of the investigated Austrian Molasse carpofloras with those from the southern Bavarian Molasse Zone demonstrates certain floristic differences. Several species and genera are missing in Bavaria and vice versa. During the Miocene there was no large-scale coal formation in the southern Bavarian Molasse Zone, which would explain the slightly different plant communities. Comparisons with a lignite mining area in NE Bavaria, north of the Molasse Zone, also discloses differences. Rich mastixioid assemblages (with many subtropical elements), which have not been recorded in the Austrian Molasse, are well-represented there. The clay pit Mataschen (Styria, S.E. Austria) has the richest Upper Miocene diaspore assemblage in the Styrian Tertiary Basin to date (about 60 taxa). The large quantities of Sinomenium cantalense (moonseed plants), the presence of Butomus (flowering rush), and Paulownia are remarkable. The investigated sedimentary profile documents a swamp forest, drowned by lake sediments and the increasing influence of a river delta which fed into the lake. The combined anatomical-morphological and biochemical study of the fossil genus Ceratostratiotes (Ceratophyllaceae or Hydrocharitaceae) yielded unexpected results. While the biochemical analyses indicate a dicotyledonous plant, the morphology and anatomy reveal close agreement with the monocotyledonous Hydrocharitaceae. Thus the systematic position of Ceratostratiotes, which is restricted to four regions around the Central Paratethys, remains a mystery.