The Sokoliska Limestone, a new regional marker horizon of coccolith laminites in the Oligocene of the Outer Carpathians : diagnostic features and stratigraphic position

Isochronous horizons of pelagic coccolith limestones are important regional stratigraphic markers in the Oligocene sequences of the Outer Carpathians. Three widely recognized limestone horizons are the Tylawa Limestones, the Jasło Limestone and the Zagórz Limestone horizons. Another regional marker horizon is described here, the Sokoliska Limestone horizon, situated between the Jasło Limestone and Zagórz Limestone horizons in the nannoplankton NP24 Zone. Its lithologic characteristics allow it to be distinguished from the other limestones, especially under the optical microscope. Its dark laminae are greatly enriched in non-calcareous material. The limestone contains tests of planktonic foraminifers, but these are much less abundant than in the Jasło Limestone. The boundaries with the marly shales above and below are often more gradational than is the case with the other limestone horizons.The Sokoliska Limestone has been recognized over a distance of ca.550 km in the Skole (Tarcãu) and Silesian units of the eastern and northern parts of the Outer Carpathians. Four sections of the Sokoliska Limestone horizonin the Polish and Romanian Carpathians are described; the exposure in the Sokoliska cliff of the Solinka River at Bukowiec was selected as the reference locality

The Tylawa Limestones – a regional marker horizon in the Lower Oligocene of the Paratethys : diagnostic characteristics from the type area

Three units of laminated coccolith limestone are used as regional chronohorizons in the Oligocene of the Outer Carpathians. Two of them – the Tylawa Limestones and the Jasło Limestone display a similar type of lamination and their discrimination is in some cases problematic. We provide a detailed mesoscopic and microscopic lithological description of the Tylawa Limestones from the type locality at Tylawa and from Rudawka Rymanowska – the best exposure in the Polish Carpathians. The finely laminated limestone layers are up to 5.5 cm thick and are dispersed through a section more than 100 m thick. They are grouped in clusters. They differ from the younger Jasło Limestone in: (1) an absence of foraminifers, (2) a mass occurrence of Reticulofenestra ornata Müller, (3) the presence of voids after pennate diatoms, (4) dark laminae which are more pronounced than in the Jasło Limestone

The Central Paratethys during Oligocene as an ancient counterpart of the present-day Black Sea: Unique records from the coccolith limestones

Four isochronous Oligocene coccolith limestone horizons from the Carpathians were examined in order to reconstruct paleoceanographic conditions in the Central Paratethys. The dominance of small and size-uniform pyrite framboids, the occurrence of low-diversity dinoflagellate cysts and coccolithophorids and the presence of biomarker molecule 28,30-dinorhopane indicate that the water column was stratified with the upper water column being relatively well oxygenated, but the bottom water being anoxic. The latter is confirmed by the fine and consistent horizontal laminations in various parts of the basin, scarcity of benthic organisms and their trace fossils. The limestones exhibit typical marine δ13C values, but are significantly depleted in 18O and enriched in 87Sr relative to contemporaneous ocean water. These isotopic compositions result from a decreased salinity of the surface waters caused by an increased riverine input. This is confirmed by the lack or impoverishment of planktonic foraminifers, presence to abundance of goniodomid dinoflagellate cysts and massive occurrence of low-diversity nannoplankton assemblages, which indicates decreased salinities as low as 17‰ and high productivity in the upper water column. These observations indicate that the limestones were formed during periods when connection of the Central Paratethys with the global ocean was limited, which impeded water exchangecausing the development of low-salinity conditions of surface water and bottom-water anoxia. During the deposition of the oldest Tylawa horizon, primary productivity was enhanced and chemocline was positioned exceptionally high in the water column. Moreover, decreased δ13C values in both carbonates and organic matter of this horizon suggest that widespread methane venting took place in the basin during NP23. All these data show that during the Oligocene the Central Paratethys experienced similar conditions to those of the current Black Sea, which can be used as a modern analogue, especially for the Tylawa horizon. Therefore, the Tylawa horizon can be perceived as a potential effect of future post-depositional processes of coccolith marls analogous to those having been deposited in the Black Sea for 2.7 kyr