Early Oligocene Continental Climate of the Palaeogene Basin (Hungary and Slovenia) and the Surrounding Area

Authors: BOGLARKA ERDEI, TORSTEN UTESCHER, LILLA HABLY, JULIA TAMÁS, ANITA ROTH-NEBELSICK, MICHAELA GREIN

Abstract: This paper concentrates on the Early Oligocene palaeoclimate of the southern part of Eastern and Central Europe and gives a detailed climatological analysis, combined with leaf-morphological studies and modelling of the palaeoatmospheric CO_2 level using stomatal and \delta^1^3C data. Climate data are calculated using the Coexistence Approach for Kiscellian floras of the Palaeogene Basin (Hungary and Slovenia) and coeval assemblages from Central and Southeastern Europe. Potential microclimatic or habitat variations are considered using morphometric analysis of fossil leaves from Hungarian, Slovenian and Italian floras. Reconstruction of CO_2 is performed by applying a recently introduced mechanistic model. Results of climate analysis indicate distinct latitudinal and longitudinal climate patterns for various variables which agree well with reconstructed palaeogeography and vegetation. Calculated climate variables in general suggest a warm and frost-free climate with low seasonal variation of temperature. A difference in temperature parameters is recorded between localities from Central and Southeastern Europe, manifested mainly in the mean temperature of the coldest month. Results of morphometric analysis suggest microclimatic or habitat difference among studied floras. Extending the scarce information available on atmospheric CO_2 levels during the Oligocene, we provide data for a well-defined time-interval. Reconstructed atmospheric CO_2 levels agree well with threshold values for Antarctic ice sheet growth suggested by recent modelling studies. The successful application of the mechanistic model for the reconstruction of atmospheric CO_2 levels raises new possibitities for future climate inference from macro-flora studies.

Keywords: Early Oligocene, Palaeogene basin, fossil flora, palaeoclimate, morphometry, carbon dioxide

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