Calcareous nannofossil biostratigraphy of the Upper Cretaceous–Lower Paleocene sequence of the Deramazan section, Sulaimani area, Kurdistan region of NE Iraq

The nature of the Cretaceous–Palaeogene boundary in the Kurdistan region of NE Iraq is still under debate. Most studies have considered the Danian sediments to be mostly missing. Another hypothesis suggests that a conglomerate represents the contact between the Cretaceous and Paleogene. We examined the boundary succession of the Deramazan section in the Sulaimani area (NE Iraq) in order to determine the calcareous nannofossil assemblages and address the biostratigraphy around the boundary. The rock strata in the studied section are characterised by alternations of olive-green to greenish-grey sandstone, siltstone, shale and marlstone interlayers in both the Tanjero (Upper Campanian–Maastrichtian) and overlying Kolosh (Paleocene–Lower Eocene) Formations. The upper part of the section includes a thick conglomerate bed. We found that deposition across the boundary was essentially continuous, with no discernible break in sedimentation. The base of Zone NP1 (base of the Kolosh Formation) was identified by the bases of Biantholithus sparsus, Cruciplacolithus spp. and Coccolithus pelagicus, plus an acme of Cervisiella operculata, which seems to indicate no hiatus. There is some reworking of Cretaceous taxa above the boundary, into NP1 and NP2. The relative abundances of the nannofossil assemblages across the boundary reflect a productive marine environment.