Calcareous nannoplankton biostratigraphy of the terminal sediments of the Magura basin – a case study of the polish sector (outer western Carpathians)

The Oligocene to Early Miocene closing of the northern sector of the Outer Carpathian sedimentary area is manifested by deposition of the Krosno synorogenic lithofacies in the Grybów-Dukla-Silesian/Sub-Silesian/Skole and Boryslav-Pokuttya basin system. The analogous Malcov synorogenic lithofacies is typical for the Pieniny Klippen Belt and Magura Basin. These lithofacies comprise the fining and thinning upwards sequences. Towards the top, the sedimentary sequences are dominated by marly pelites. In the Pieniny Klippen Belt, as well as in the Krynica and Rača zones of the Magura Basin, the deposition of the Malcov lithofacies was initiated during the NP24 and persisted to NP25 Zone. In the northern part of the Magura Basin (Siary Zone) the youngest deposits (so called Supra-Magura beds) belong to the NP24 Zone. The most important species to determine the NP24 zone in the region is Cyclicargolithus abisectus, and for NP25 – Sphenolithus conicus. During the Late Oligocene (NP25/NN1) the frontal part of Magura Nappe were thrust northwards onto the terminal Krosno flysch basin. The clastic material derived from eroded front of the Magura Nappe has been found in the Krosno shally facies of the Silesian Basin. The northwards thrusting of the Magura Nappe was also accompanied by formation of the piggy-back basin on the Magura Nappe, filled with synrogenic turbidites of the Zawada and Kremná formations – NN1 and NN2 zones. These nannofossil associations are characterised by the presence of Sphenolithus delphix (NN1) and Sphenolithus disbelemnos (NN2) while the species of Dictyococcites bisectus is absent. At the same time the level of reworked species is high.