Age and evolution of depositional environments of the supra-evaporitic deposits in the northern, marginal part of the Carpathian Foredeep: micropalaeontological evidence

Abstract

A rich assemblage of microfossils, including foraminifera, ostracodes and bolboforms (calcareous phytoplankton) have been found in the supra-evaporitic deposits of the Pecten Beds (Upper Badenian) and Krakowiec Clays (Sarmatian) of Middle-Miocene age, which occur in the Jamnica S-119 borehole near Tarnobrzeg, in the central part of the Carpathian Foredeep. Environmental conditions have been deduced from these microfossils. Comparison with other parts of the Carpathian Foredeep shows that microfauna distribution depended on location within the sedimentary basin and on hydrological conditions. Poorly-diversified and specific microfossils were associated with evaporates and overlying sediments (particularly within the lower Pecten Beds and Krakowiec Clays), indicating poorly-oxygenated near-bottom waters. Possibly, "Upper-Badenian" and"Sarmatian" biofacies had already differentiated by the end of the Badenian. Distribution of the Upper Badenian microfauna and bolboforms in the Polish part of the Carpathian Foredeep and beyond shows that there was faunal exchange between the eastern and western parts of the Polish section of the Carpathian Foredeep, and indicates connection between the Central Paratethys and Mediterranean basin areas.