Calcareous nannofossil biostratigraphy and paleogeographic significance in the lower Maastrichtian of the Miechów Trough (southern Poland)

Abstract

: Ciołko, U. and Gaździcka, E. 2022. Calcareous nannofossil biostratigraphy and paleogeographic significance in the lower Maastrichtian of the Miechów Trough (southern Poland). Acta Geologica Polonica , 72 (3), 331–352. Warszawa. Biostratigraphic analysis of calcareous nannofossils from the Pełczyska section in the Miechów Trough (south - ern Poland) has revealed that the entire section covers the lowermost Maastrichtian. The UC16b TP Tethyan subzone is designated based on the presence of Broinsonia parca constricta Hattner, Wind and Wise, 1980 , reworked remains of Uniplanarius trifidus (Stradner) Hattner and Wise in Wind and Wise, 1983 and the simul - taneous lack of Eiffellithus eximius (Stover) Perch-Nielsen, 1968. The studied section spans also the interval between the LO of Zeugrhabdotus praesigmoides Burnett, 1997 and the FO of Prediscosphaera mgayae Lees, 2007 (UC16 S3 Boreal subzone). Quantitative analysis of nannofossil assemblages has shown the dominance of cold water species (up to 50%), e.g., Micula decussata Vekshina, 1959, Prediscosphaera spp., Arkhangelskiella spp., Calculites obscurus (Deflandre) Prins and Sissingh in Sissingh, 1977 and Lucianorhabdus cayeuxii Deflandre, 1959. In the early Maastrichtian, the studied area was more influenced by cool water masses from the Boreal Province rather than by warm water from the Tethyan Province. The significant predominance of cold water taxa and the elevated presence of Prediscosphaera cretacea (Arkhangelsky) Gartner, 1968 also supports the hypothesis of climate cooling in the early Maastrichtian.