Foraminiferal and calcareous nannoplankton biostratigraphy of the upper Badenian–lower Sarmatian strata in the SE Polish Carpathian Foredeep

Authors

  • Danuta Peryt Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa
  • Małgorzata Garecka Polish Geological Institute-National Research Institute, Carpathian Branch, Skrzatów 1, 31-560 Kraków
  • Tadeusz Marek Peryt Polish Geological Institute-National Research Institute, Rakowiecka 4, 00-975 Warszawa

Keywords:

Middle Miocene, Carpathian Foredeep Basin, foraminifera, nannofossils, palaeoenvironments.

Abstract

The Badenian/Sarmatian boundary in the Central Paratethys has been traditionally identified by the faunal turnover recording an important environmental change possibly controlled by the change from marine to brackish conditions. The strata below the Badenian/Sarmatian boundary in the northern Carpathian Foredeep are included into the Pecten beds, and those above it into the Syndesmya beds. Foraminiferal study of the Babczyn 2 borehole which is one of the crucial sections in the northern Carpathian Foredeep, well-known for the depositional age of rhyolite tuff within the Pecten beds dated by Śliwiński et al. (2012) at 13.06 ±0.11 Ma, indicated that in fact the boundary occurs within the Syndesmya beds. This conclusion is based upon the rapid change from a stenohaline foraminiferal fauna to a euryhaline one, and the appearance of the species Anomalinoides dividens, the taxon regarded as the marker for the Sarmatian. In the Babczyn 2 and Cieszanów 1 (located ~2.5 km basinward of Babczyn 2) boreholes, Anomalinoides dividens appears 3.1–3.8 m above the replacement of stenohaline by euryhaline foraminifers. The calcareous nannoplankton study shows that the upper Badenian and the lower Sarmatian strata in the studied sections represent the NN6, undivided NN6-NN7, and NN7 zones.

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Published

2021-04-08

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