New biostratigraphic data on the Ropianka Formation in the Przemyśl area (Skole Nappe, Polish Outer Carpathians) – a clue to understanding the timing of exotic material redeposition

Abstract

The geology of the Carpathian orogen in the Przemyśl area shows a diverse array of rock ages and tectonics. However, due to complicated tectonic settings and limited exposures, establishing the precise ages of selected sections and their structural arrangement is challenging. A particularly contentious aspect is the uncertain age of the exotic-bearing layers in the region, with previous age dates ranging from Neocomian to Miocene, leading to significant age discrepancies even for the same sections. Therefore, the need for well-defined age determinations is crucial. To address this issue we established precise biostratigraphic constraints on selected sections in the northern part of the Skole Nappe, specifically within the Ropianka Formation developed as marly and silty deposits with carbonate sandstones and exotic material including large olistoliths. Planktonic and calcareous benthic foraminifera from the exposures studied indicated the lower upper Maastrichtian, embracing the interval of the Racemiguembelina fructicosa and lower part of the Abathomphalus mayaroensis zones. Additionally, re-evaluation of the data of Bukowy and Geroch (1956) from the Iwanowa Hill section indicated its late Maastrichtian age, not the early Maastrichtian as previously inferred. Based on this new biostratigraphic data, the deposits of the Zielonka section are here reclassified to belong to the Leszczyny Member, and not the Paleocene Wola Korzeniecka Member as proposed by Gucik (Geroch et al., 1988). The sections studied seem to mark the lower age-limit of the redeposition of exotic material cropping out in the marginal part of the Gruszowa-Prałkowce Thrust Sheet