International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Last occurrence of Abathomphalus mayaroensis (Bolli) foraminiferid index of the Cretaceous—Paleogene boundary: the calcareous nannofossil proof

Published: Jun 2015

Pages: 181 - 195



Abstract: In the Gaj section (Polish Carpathians, Skole Nappe, Ropianka Formation), the Late Maastrichtian calcareousnannofossil biostratigraphy is compared with foraminiferal zonation based on the occurrence of the planktonic foraminiferidindex species Abathomphalus mayaroensis. It appears that the LO of A. mayaroensis, which has been used previously inthe studied section as the possible K/Pg boundary indicator is located below the boundary. The disappearance ofA. mayaroensis along with other planktonic foraminiferids before the Cretaceous—Paleogene (K/Pg) boundary massextinction event may be a consequence of the Late Maastrichtian rapid warming pulses. Moreover, the Paleogene agecannot be supported by the FO of the benthic foraminiferid Rzehakina fissistomata, because it first appears together withthe nannofossil Ceratolithoides kamptneri (zonal marker for the latest Maastrichtian UC20cTP Zone). According to thepresent study, the whole studied section represents the lower Upper to the upper Upper Maastrichtian UC20bTP and UC20cTPnannofossil zones, so that it corresponds to the lower-middle part of the planktonic foraminiferal A. mayaroensis Zone,which, according to the scheme by Caron (1985), should extend up to the K/Pg boundary.

Keywords: biozonation, Cretaceous—Paleogene boundary, nannofossils, foraminiferids, late Maastrichtian warming

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