Use of dispersed palynomorphs and organic facies for the reconstruction of Miocene terrestrial ecosystems in eastern Austria.

The Miocene in Austria was characterized by orogenic movements resulting in a N-directed compressional Alpine foreland basin (Molasse basin) and numerous intramontane basins of varying size in the SE part of the orogenic wedge. The geomorphology and geometry of the basin complexes and the evolving orogen were constantly changing. These variations controlled both the style of sedimentation in the basins, which is characterized by an upward trends from marine to terrestrial conditions, and the life which inhabited and evolved in the local ecosystems in the area. Typical terrestrial deposits preserved in both the intramontane basins and Molasse basin are brackish estuarine and fluvial-lacustrine coal/oil shale-bearing sediments. The organic and plant fossil rich (palynomorphs, diaspores and leaves) sediments bear witness the former plant life that adapted to the environmental changes, as contemporaneously new space for colonisation developed and already established biohabitats vanished due to uplift. Plants are early and rapid pioneers on newly formed substrates and, depending on the climate and edaphic factors, such as relief, soil composition, drainage and moisture, the pioneer communities tend to evolve into a more sustained vegetation form or retain their pioneering status. Two major divisions in vegetation can be made: 1. Azonal wetland habitats, including clastic swamps and organic peatlands situated within the basins, and 2. Zonal, better drained habitats that occur in the hinterland; these are often regions of non-deposition or erosion. Plant fossils are mostly of (par-) authoclithonous azonal origin, admixed with a minor amount of allochthonous zonal plant taxa, depending on the proximity of the depositional site to the zonal vegetation. Palynomorphs, because of their minor size and dispersing mechanisms, are very good representatives for both the azonal and zonal vegetation and, therefore, together with organic facies and sedimentological data, form a good base for reconstructing the different ecosystems. Furthermore, the combination of these data sets are vital for modelling plant habitat developments and vegetation trends, in order to obtain the influence of both palaeoclimatic and geotectonic changes. Aims: The aims of this project are: 1. To revise, summarise and complete previously started palynological work from selected Miocene sites and to look for new, suitable sites. 2. To use this data to produce a comprehensive palynological and organic facies data base for the Molasse basin and intramontane basins through the whole Miocene. 3. This will then be compared with other palaeobotanical. databases (eg. diaspores and leaves) to determine the complete floral assemblages in the various localities and stratigraphic horizons. 4. These assemblages will then be used, in conjunction with sedimentological data, to reconstruct the ancient ecosystems. 5. A further aim is to test the biostratigraphic value of Miocene palynomorphs. 6. The comparison of the floras from the intramontane basins with those from the Molasse basin will be made to determine how palaeogeographical and local variations in palaeoclimatological conditions influenced the composition of the flora. 7. Finally, the palynological data base, together with the diaspore (project FERGUSON & MELLER) and leaf (project KOVAR-EDER) databases, should cover the entire terrestrial Miocene and can be applied to establish trends/changes in the vegetation and how they were triggered