Late Badenian foraminifers from the Vienna Basin (Central Paratethys): stable isotope study and paleoecological implications

Abstract

Late Badenian foraminifers from the Vienna Basin (Central Paratethys): stable isotope study and paleoecological implicationsPaleoecological interpretations based on stable isotope study of benthic (Uvigerina semiornata) and planktonic (Globigerina bulloides, Globigerinoides trilobus) foraminiferal shells from the Paratethys Vienna Basin (southwestern Slovakia) are presented. The study was performed on sediments of the Devínska Nová Ves-clay pit deposited during the Middle and Late Badenian (Middle Miocene). Our δ13C data show an enhanced nutrient input to the water column and the organic matter accumulation at the bottom of the Vienna Basin. The remineralization of accumulated organic matter on the sea floor resulted in the formation of oxygen-depleted zones, where no oxic indicators but the oxygen-deficiency tolerant species were found. Positive benthic δ18O signal can be attributed to the influence of the global cooling recognized in the world-ocean during the Middle Miocene. At the same time, variations observed in the water column are interpreted as reflecting the local temperature and salinity changes resulting from the fluvial and rain inflow. The differences between surface and bottom water temperature reflect the stratification of the water column. Such stratification might be related to the isolation process of Central Paratethys in the Badenian. This study confirms that δ13C and δ18O are not always in isotopic equilibrium with the ambient water but are also influenced by vital effects (respiration, symbiont photosynthesis …). The vital effects led to the incorporation of isotopically light metabolic CO2intoGlobigerina bulloidesresulting in high similarity between δ13C values ofUvigerinaandGlobigerina. It has been shown that the extremely high δ13C and very low δ18O ofGlobigerinoides trilobusclearly imply the influence of algal photosymbionts.