Chitinozoans and acritarchs from the Ordovician of the Skibno 1 borehole, Pomerania, Poland: implications for stratigraphy and palaeogeography

Biostratigraphical results of this palynological study agree with those of previous research on graptolites from the Ordovician of the Skibno 1 borehole in the Koszalin–Chojnice Structural Zone, Polish portion of the Pomerania Terrane. They indicate that the investigated core interval can be attributed to the uppermost Llanvirn (Llandeilo) – lower Caradoc, and correspond to the teretiusculus and gracilis through the multidens graptolite biozones. Recovered chitinozoan species, including Belonechitina robusta, Conochitina chydaea, C. dolosa, Lagenochitina aff. capax, Spinachitina bulmani, and the index species Laufeldochitina stentor are restricted to the upper Llanvirn – lower Caradoc, the latter species delimits the stentor chitinozoan biozone (upper Uhaku and Kukruse stages). The following identified acritarchs are regarded as biostratigraphically significant: Goniosphaeridium splendens, Ordovicidium elegantulum, O. heteromorphicum, O. nanofurcatum, O. nudum, and are characteristic for the Caradoc. The presence of conodont Scabbardella altipes and ichnofossil Alcyonidiopsis pharmaceus, both characteristic of high palaeolatitudes, as well as lithological similarities between the investigated strata and their equivalents from Rügen indicate that Pomerania could have been situated at relatively high latitudes during the upper Llanvirn to lower Caradoc. These observations together with palynological results support a hypothesis that Pomerania was a terrane derived from Avalonia and accreted to the margin of the East European Craton.