Lower Carboniferous conodont biostratigraphy ln the northeastern part of the Moravia-Silesia Basin

The conodont fauna contained in carbonate rocks pierced by boreholes in the area between OIkusz and Sosnowiec (southern Poland) is recognized as indicative of Middle Tournaisian to late Visean age. The three new species of Gnathodus and Paragnathodus , viz. Gnathodus austini sp. n., Gnathodus praebilineatus sp. n., and Paragnathodus cracoviensis sp. n., provide a clear understanding of the origin of Visean gnathodid conodonts. To correlate the Lower Carboniferous deposits in the OIkusz and Sosnowiec area, the preliminary standard conodont zonation of SANDBERG & al. (1978) and LANE, SANDBERG & ZIEGLER (1980) is adopted, and two conodont zones, the austini and the bilineatus , are introduced to extend the zonal scheme upward to the late Visean. On the basis of this biostratographic framework, the diachronous nature of the facies is indicated, and this precludes simple correlation of lithological and biostartigraphic units. The significant stratigraphic gap between the Devonian and the Lower Carboniferous deposits covers the interval between the Middle and/or Upper costatus Zone (uppermost Famennian) and the crenulata Zone (Middle Tournaisian). In some places, however, the presence of the sandbergi Zone at the base of the Lower Carboniferous sequence is also suggested.