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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

Woyda Jan, Waśkowska Anna, Remin Zbyszek

Geological Quarterly

2023

Vol. 67, No. 4

art. no. 45

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.

The K-Pg boundary section at Nasiłów, Poland : stratigraphic reassessment based on foraminifers, dinoflagellate cysts and palaeomagnetism

Remin Zbyszek, Cyglicki Michał, Barski Marcin, Dubicka Zofia, Roszkowska-Remin Joanna

Geological Quarterly

2021

Vol. 65, No. 3

art. no. 45

The Nasiłów section represents the uppermost part of the Middle Vistula River section, a classical Polish extra-Carpathian Cretaceous section, and gives access to the Cretaceous-Paleogene (K-Pg) boundary interval. Despite many papers that have been published so far, our newly collected data shed new light on the completeness of biostratigraphic and sedimentary records of the K-Pg at that site. The Nasiłów section encompasses the upper Maastrichtian regional XII and XIII foraminiferal assemblage zones and the lower Danian P0?-Pα standard planktonic foraminiferal zones. The K-Pg boundary is placed at the top of a phosphatic layer. The grey marly chalk unit, never before subjected to examination of biostratigraphically important taxa, displays blooms of guembelitrids pointing to the uppermost Maastrichtian (XIII foraminiferal assemblage Zone) as well as of planktonic and benthic foraminifers of a reduced test size. Such foraminiferal dwarfism is commonly observed near the end of the Cretaceous and interpreted as a response to the Deccan volcanism (possible 2nd phase) that caused climate changes and ocean acidification. The terminal Maastrichtian age of the marly chalk unit is additionally supported by an acme of the dinoflagellate cyst Palinodinium grallator, together with Tallasiphora pelagica and Disphaerogena carposphaeropsis. The “Greensand”, a distinct glauconite-quartz sand unit, contains exclusively terminal Maastrichtian planktonic foraminifers and dinoflagellate cyst assemblages. Individual specimens of Danian age are interpreted to be either an effect of contamination or were translocated down by burrowers into the Greensand. The lowermost portion of the Siwak (informal lithostratigraphic unit) demonstrates an early Danian age based on the co-occurrence of the common planktonic foraminifers Globoconusa daubjergensis, Guembelitria cretacea, Muricohedbergella monmouthensis, M. planispira, Planoheterohelix globulosa, Parvularuglobigerina extensa and P. alabamensis. The last occurrence of Palynodinium grallator and the first occurrences of Carptella cornuta and Senoniasphaera inornata, recorded directly above the phosphatic layer, support the same age assignment. The new palaeomagnetic data cannot prove remagnetization at the boundary interval, in contrast to previous research which gave support to a hiatus in the critical interval.