Miocene terrestrial environments reflected in leaf assemblages.

Research project P 13741 Miocene Ecosystem Changes in the E-Alps - Leaf Assemlages Johanna EDER-KOVAR 28.06.1999 In eastern Austria numerous fluvial/lacustrine complexes developed during Neogene time in basins characterized by different evolutionary histories. These deposits are rich in plant-bearing localities, some. having been known since the 19th century, some only being discovered during the past decade. Modem geodynamic. investigations of the evolution of the eastern Alpine region have partly unraveled the history of these basins. This represents a unique starting point to study terrestrial ecosystem changes in the context of geodynamic processes. The proposed investigations will focus on plant deposits (leaves) in fluvial/lacustrine complexes of restricted time intervals (late Early/Early Middle Miocene, Karpatian/Badenian; Middle Miocene, Badenian; Late Miocene, Pannonian): the Fohnsdorf and Parschlug Basins (small intramontanous, pull-apart basins along the Mur/Mürz; fault system), the Molasse Basin north of the Alps (Alpine foreland basin), and the Eastern Styrian Basin (Pannonian Basin System). The fossil leaf assemblages will be evaluated systematically-taxonomically. The determinations will be based on grossmorphological and, to the extent possible, on cuticular structures. Selected groups will be investigated in separate studies (Acer-maple, Trapa-waternut, Salicaceae-willow family). The floristic spectra will be interpreted palaeoecologically including the taphonomic and sedimentological information potential of the plant-bearing sites. These results will be compared and combined with those from the related palaeobotanical projects investigating fruits/seeds and pollen/spores. The vegetational development accompanying the fluvial systems will be reconstructed based on the fossil record. Palaeoclimatic parameters will be determined via the coexistence approach (MOSBRUGGER & UTESCHER 1997). The results from different basins within one time interval and from different stratigraphic levels will be compared and interpreted in the context of the respective basin evolution. Potential factors for existing differences (edaphic, facial, tectonic-geodynamic, climatic, stratigraphic ones) will be investigated. The palaeobotanical results will be tested against the geodynamic models obtained in the course of the sedimentological-geodynamic project of this cluster.

Miocene floras from different basins have been investigated to improve the understanding of the diversity of terrestrial environments: Hinterschlagen (Hausruck lignite area, Upper Austria, Molasse basin), Pellendorf (Mistelbach District, Lower Austria, Vienna basin), Mataschen (near Fehring, Styria, Eastern Styrian basin) - all Pannonian, Parschlug (near Kapfenberg, Styria, Norian Depression) - Karpatian/Badenian. Hinterschlagen reflects shallow aquatic and swampy floodplain habitats of a river system. In Pellendorf nearshore vegetation at the northwestern margin of Lake Pannon is preserved. The records of extensive stands of the water willow (Decodon restricted to Eastern Northamerica today) and of species-diverse aquatic plant communities are unique. The environmental setting may be compared to the Volga delta at the northern margin of the Kaspian sea today. In Mataschen a basal level testifies swamp environments while a higher level of the section there yielded mainly plants from the hinterland. This flora is the species-richest among the Pannonian leaf floras from Austria. The diversity of laurophyllous taxa (Lauraceae, Fagaceae) is exceptional for the Central European Upper Miocene record. The Pannonian floras indicate warm-temperate and humid climatic conditions comparable to parts of SE- Asia and SE-North America today. For the first time, the famous flora of Parschlug was treated monographically. Physiognomically sclerophyllous woody taxa are diversified indicating drier climatic conditions than in earlier and later Miocene times. Salix hausruckensis (willow), Trapa ungeri (waternut)(both from Hinterschlagen), and Mikia pellendorfensis (Pellendorf) are among the newly discovered taxa. The latter possibly constitutes the floating leaves of fossil Hemitrapa (waternut relative). The genus Prinsepia (Rosaceae, today East Asia) detected in Parschlug, is new in the fossil European leaf record. Maples were investigated monographically focussing on the species diversity, ecology, and distribution in time and space. The history of the Austrian record of waternuts was put into an European context and the records of willow and poplar in Austria were critically reviewed. The investigation of wetland taxa clearly showed that during the Miocene, the flora of wetland environments underwent significant changes relevant for biostratigraphic and climatic interpretation.