Chitinozoan biozonation of the Ordovician succession in the borehole Ketrzyn IG 1 (NE Poland)

The Ordovician carbonate sequence in the Kêtrzyn IG 1 borehole (depth 1544,5–1612,7 m) contains diversified, abundant Chitinozoa assemblage. 48 taxons were identified which document 6 standard zones of regional Baltoscandian scale: stentor, hirsuta, barbata, fungiformis, bergstroemi, fragilis. In the two zones fungiformis and bergstroemi were identified: in the fungiformis —the angusta subzone and in the bergstroemi — the cervicornis subzone (fig. 3). Definition of extent and boundaries as well as position in the profile of the distinguished zones and subzones enables precise correlation of the Ordovician carbonate sequence of the Kêtrzyn IG 1 borehole with the isochronous profiles in the adjacent Polish areas (Proniewicze IG 1, Klewno 1, Sokolica 1 borehole), in Estonia (Rapla 1, Tartu (453), Taga–Roostoja (25A) (borehole, and in western Volhynia, Ukraine) Kowel 1 (no 5415) borehole.