Basin-scale paleobiogeography and paleoecology: an example from Karpatian (Latest Burdigalian) benthic and planktonic foraminifera and calcareous nannofossils from the Central Paratethys

We present the paleobiogeography and ecology of benthic and planktonic foraminifera and calcareous nannoplankton during the Karpatian (Latest Burdigalian) in the Austrian part of the Central Paratethys. Results are based on quantitative data of assemblages from the Molasse and Styrian Basins. Our data suggest that, although adjacent, the two basins underwent different paleoceanographic evolution during the Karpatian. Dysoxic bottom waters characterized the Molasse Basin, together with reducing environments, which produced the formation of pyritized levels. In the Styrian Basin, intense volcanic activity enriched surface waters in nutrient and produced strong primary productivity. Reduced planktonic foraminiferal abundance and dominance of agglutinated benthic forms in the Styrian Basin can be attributed to paleoceanographic conditions. The planktonic-depleted assemblages bias the paleodepth estimation by 100P(P + B) in the Styrian Basin and new tools for assessing paleodepth are needed. This study shows that paleobiogeography of foraminifera and calcareous nannoplankton is strictly related to local ecological conditions in enclosed basins and demonstrates that quantitative ecological studies are the best way to monitor the biogeographic evolution of enclosed basins. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.