TY - JOUR A1 - Kurschner,W.M. A1 - Kvacek,Z. T1 - Oligocene-Miocene CO2 fluctuations, climatic and palaeofloristic trends inferred from fossil plant assemblages in central Europe JF - Bulletin of Geosciences JA - Bull. Geosci. Y1 - 2009 VL - 84 IS - 2 SP - 189 EP - 202 CY - Prague PB - Czech Geological Survey SN - 1803-1943 (online), 1802-6222 (print) AV - Free KW - vegetation KW - CO2 concentrations KW - Late Oligocene KW - Miocene KW - palaeoclimate AB - Stomatal frequency data from four independently calibrated woody plant species reveal pronounced CO2 fluctuations since the Late Oligocene. CO2 fluctuations in the Early to Middle Miocene are of such a magnitude that they may have driven much of the temperature variation and major climatic events. Warm intervals such as in the Late Oligocene and the mid-Miocene climatic optimum are characterized by significantly elevated CO2 levels of at least about 500 ppmv. Elevated CO2 levels may have also increased the diversity in C3 plant communities. The major cooling events in the Early Miocene and the late Middle Miocene are characterized by CO2 decreases down to 340 ppmv and 280 ppmv, respectively. A comparison with marine and continental climate records indicates that much of the long-term climate variation was linked to changes in atmospheric CO2. The CO2 fluctuations may have influenced ancient diversity of plant communities indirectly via changes in climate parameters, such as temperature or precipitation, seasonality, and/or directly by affecting plant photosynthetic performance. In the Oligocene, the type of vegetation is dominated by thermophilous paratropical-subtropical elements including palms but also with a considerable proportion of deciduous trees. The vegetation during the Oligocene-Miocene transition is slightly impoverished in species richness. There are profound differences in the physiognomy of elements, which are predominantly deciduous. During the Early to early Middle Miocene (15-17 Ma), plant assemblages are characterized by subtropical Notophyllous Evergreen forest vegetation with a maximum in species richness reflecting the middle Miocene climate optimum (Late Mastixioid floras sensu Mai). In the late Middle Miocene (13-14 Ma), the floras are less diversified, the woody elements are mostly dicots, both evergreen and deciduous and the vegetation type belongs to the Mixed Mesophytic Forest with a higher proportion of evergreen elements but with exceptional macrofossils of palms. The youngest flora of the latest Middle Miocene is much less diversified in contrast to the previous time interval. Generally, more diversified deciduous broad-leaved trees predominate while the lauroid elements become much less dominant. The diversity trends in central Europe suggest that the highest diversity found during the Late Oligocene and Middle Miocene most likely resulted from optimal climate conditions that expanded the area available for thermophilous, paratropical-subtropical vegetation into the mid-latitudes. The Oligocene-Miocene vegetation history is hard to explain with permanent low CO2 conditions (~200-280 ppmv) as suggested by the marine CO2 proxy records. ER -