How many “black flysches” can be distinguished in the Grajcarek thrust-sheets of the Pieniny Klippen Belt in Poland

The age of the “black flysch” deposits occurring in the contact zone of the Magura Nappe and the Grajcarek thrust-sheets of the Pieniny Klippen Belt (PKB) in Poland has been a matter of a long lasting discussion. In the PKB, black shales (“Black Cretaceous”) of a Barremian to Albian age with intercalations of thin- to thick-bedded muscovite sandstones and spotty marls, overlain by the Upper Cretaceous red shales were distinguished in the 30-ties of the last century. Later on, basing on some macrofauna evidence, these beds were assigned to the Middle Jurassic. In stratigraphical scheme of the PKB these beds were called the “Aalenian Flysch” and described as the Szlachtowa (Toarcian-Aalenian) and Opaleniec (Bajocian) formations. Another black flysch deposits were distinguished as the Wronine (Lower Albian) and Hulina (Albian-Middle Cenomanian) formations at the base of the Upper Cenomanian-Campanian red shales. Such a division has been established by Birkenmajer in a standard scheme for PKB. The presence of two black flysches was already questioned by Sikora in 1962, who documented that the beds assigned to the Aalenian Flysch, represented Albian-Lower Cenomanian deposits, passing upwards into the Upper Cretaceous red shales. For the last few years, the authors have studied and sampled several sections which record the relation between the “black flysch” and Cretaceous red shales in the Grajcarek thrust-sheets. In all the studied sections “the black flysch” appears in the core of imbricated folds or thrustsheets, whereas the limbs are composed of the Upper Cretaceous deposits. The transitional beds between the “black flysch” and the Upper Cretaceous red shales are composed of green and black, bituminous shales with manganese oxide coatings, green radiolarites with pirite framboides, cherty limestones, and finally very thin layers of dark, non-calcareous shales. In the cherty limestone the Albian-Cenomanian calcareous nannoplankton was found. Biostratigraphical investigations have revealed similar type and sequence of microfauna assemblages in all the studied sections. It should be stressed that significant redeposition of Jurrassic? calcareous benthic foraminifera, molluscs, sponge spicules and elements of crinoids has been observed in the microfaunal assemblages recovered from the black flysch turbiditic sequences. The Cretaceous age (Albian-Cenomanian) of the black flysch is confirmed by the presence of agglutinated foraminifera such as Hippocreppina depressa, Trochammina abrupta, Bulbobaculites cf. problematicus. The green shales with manganese coating contain abundant radiolaria in various state of preservation and finely, the Cretaceous red shales the assemblages with characteristic agglutinated taxa Tritaxia gaultina and Uvigerinammina jankoi.Taking into account both the lithostratigraphical and foraminiferal data, the authors conclude that only one Albian-Cenomanian black flysch complex should be distinguished in the Grajcarek thrust-sheet of the Pieniny Klippen Belt in Poland. Such a sequence of deposits is typical of the Outer Carpathian basins and records the global Mid-Cretaceous phenomena in the world ocean followed by the Cretaceous Oceanic Red Beds (CORB) deposition.
   Acknowledgements: The research was financially supported by the Jagiellonian University grant DS/INGUJ/2010/808