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 Jaslo Limestone and the Zagorz Limestone horizons. Another regional marker horizon is described here, the Sokoliska Limestone horizon, situated between the Jaslo Limestone and Zagorz 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 Jaslo 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 (Tarcău) and Silesian units of the eastern and northern parts of the Outer Carpathians. Four sections of the Sokoliska Limestone horizon in 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.