Oligocene—Middle Miocene Depositional Sequences of the Central Paratethys and their Correlation With Regional Stages

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Abstract
Detailed sequence stratigraphic analysis allowed the interpretation of seventeen depositional sequences in the Oligocene through middle Miocene succession of the Pannonian Basin (Hungary), the largest basin of the central Paratethyan area (central/eastern Europe). Depositional sequences were identified based on the analysis of published geological descriptions of outcrops and study of 3,000 km of 2D reflection seismic profiles and 45 hydrocarbon exploration wells. Eight depositional sequence boundaries coincided with regional stage boundaries; and additional nine depositional sequence boundaries were identified within the regional stages. The sequences were stratigraphically positioned on the basis of calcareous nannofossil data from 26 wells. Within the constraints of the biostratigraphic resolution in this interval, the stratigraphic position of the sequences correlates well with the previous records of depositional sequences (Haq et al., 1988). Three sequences, one in the Rupelian Stage and two in the Burdigalian Stage, were not identified by Haq et al. (1988). The examined regional stages correlate within the Paratethyan region, from Switzerland to the Caspian Sea and show a direct correlation with the standard stages. Stage boundaries typically correlate with episodic closures of connections between the European epicontinental seas from Oligocene through middle Miocene time. These closures are interpreted to result from short-term glacio-eustatic falls that overprint longer-term local tectonics. Depositional sequences are believed to result from glacioeustasy superimposed on a tectonic signal. The results, obtained in this study, and compared with oxygen isotope records (Abreu and Haddad, this volume), show a close agreement between the number and the stratigraphic position of oxygen isotope events and sequences. This supports that the major driving mechanism of depositional sequence boundary formation is glacioeustasy rather than a local or regional tectonic mechanism, and the identified sequences in this study may thus be global in nature.

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