The Grybów tectonic window belongs to the Grybów Unit of the Fore-Magura Group of units. This tectonic window is located in the marginal part of the Magura Nappe, and is composed of Oligocene — Grybów Marl Formation and Cergowa Beds. On the basis of calcareous nannoplankton investigation the Grybów Marl Formation has been assigned to Zone NP24, while the Cergowa Beds belong to Zones NP24–NP25. The Oligocene sequence of the Grybów tectonic window (Grybów Unit) display strong similarities to sediments of similar age in the inner part of the Dukla Unit in the Polish, East Slovak and Ukrainian sectors of the Outer Carpathians. On the basis of these similarities it is supposed that the Grybów Unit continues towards the south-east as an innermost part of the Dukla Unit (Ślaczka 1971), and further on into the Ukrainian Carpathians as the Dusino (Berezna) Subunit within the inner part of the Dukla Unit.