International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

EXOTICS-BEARING LAYER IN THE OLIGOCENE FLYSCH OF THE KROSNO BEDS IN THE FORE-DUKLA ZONE (SILESIAN NAPPE, OUTER CARPATHIANS), POLAND

Pages: 159 - 171

Authors: KRZYSZTOF BAK, JACEK RUBINKIEWICZ, MALGORZATA GARECKA, ELZBIETA MACHANIEC, BEATA DZIUBINSKA

Abstract: A layer with exotic blocks has been found in the flysch of the Krosno Beds, in the Fore-Dukla Zone (the southernmost part of the Silesian Nappe in the Bieszczady Mts, Polish Outer Carpathians). It has been traced over a distance of 1 km near Wetlina (the Bieszczady Mts), in the southernmost exposed tectonic slice. The exotic blocks include crystalline schist (quartz-chlorite-muscovite-orthoclase schist with tourmaline and garnet) and three types of limestones: 1/ massive, sparitic, partly siliceous limestone, with numerous calcite veins; 2/ micritic limestone with rare planktic (Globigerina-like) foraminiferal tests; 3/ bioclastic limestone with numerous tests of small and large foraminifers, coralline algae (Rhodophyta), bivalves, bryozoans and rare echinoid spines. The exotics are embedded in light- and dark-grey argillaceous, partly sandy, calcareous matrix, together with a few small angular pebbles of grey mudstones and very fine-grained sandstones, which resemble lithological types of the Krosno Beds. The described rocks are similar to those found as exotic blocks in the Krosno Beds in neighbouring areas (Roztoki Dolne and Ustrzyki Górne) of the Central Carpathian Depression (Silesian Nappe). Calcareous nannoplankton from the exotic-bearing layer and neighbouring deposits show that they are not older than the NP24 Zone (late Kiscellian), below the isochronous marker horizon of the Jaslo Limestone. It may correspond to the Tenuitella munda Zone of Olszewska (1997, 1998), proposed for the Polish part of the Central Paratethys. The source area of the layer with exotics (islands with narrow shelf mafgins), probably lay to the south and south-east, was built mainly of crystalline rocks, and partly covered by various types of carbonate Eocene-Oligocene rocks. The deeper parts of the island slopes were covered with Cretaceous-Paleogene sediments, related to deep-water sedimentation in the marginal zone between the Dukla and Silesian subbasins. These deep-water deposits have been partly eroded during the submarine mass movements descending to the Silesian Subbasin.

Keywords: Outer Carpathians, Silesian Nappe, Fore-Dukla Zone, Oligocene, Krosno Beds, Foraminifera, calcareous nannoplankton, dinocysts, exotic rocks

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