GRANICA OLIGOCEN/MIOCEN W POLSKICH KARPATACH ZEWNĘTRZNYCH NA PODSTAWIE NANOPLANKTONU WAPIENNEGO

Abstract

OLIGOCENE/MIOCENE BOUNDARY IN THE POLISH OUTER CARPATHIANS BASED ON CALCAREOUS NANNOPLANKTONAbstract. The aim of this work was to establish the Oligocene/Miocene boundary in the eastern part of the Polish Outer Carpathians on the basis of calcareous nannoplankton analysis. The investigations focused on the Menilite-Krosno Series of the Silesian and Skole Units overlying the Jasło and/or Zagórz limestone chronohorizons. In the Silesian Unit, the Oligocene/ Miocene boundary is placed in the upper part of the Lower Krosno Beds. In the Otryt facial region (southern part of the Silesian Unit), this boundary runs within the upper part of the shaly–sandy Supra–Otryt series of the Lower Krosno Beds. In the southern part of the Lesko facial region, the boundary is established within a series of thick-bedded sandstones and fine-rythmical turbidite deposits of the Lower Krosno Beds. In the northern part of this region, the series is replaced by thick-bedded sandstones of the Lesko facies. Miocene taxa were recorded in the upper part of these deposits. In the southern part of the Skole Unit the Oligocene/Miocene boundary runs within the lower part of the Lower Krosno Beds, whereas in the more northern and western parts of the unit – within the Menilite Beds. Among taxa proposed as indicative for the Oligocene/Miocene boundary, Helicosphaera mediterranea Müller, Helicosphaera recta Haq, Helicosphaera scissura Miller, Dictyococcites bisectus (Hay, Mohler et Wade) Bukry et Percival, Zygrhablithus bijugatus Deflandre, Sphenolithus delphix (Bukry) were recorded.