Maastrichtian-Thanetian planktonic foraminiferal biostratigraphy and remarks on the K-Pg boundary in the southern Kocaeli Peninsula (NW Turkey

Abstract

The Kocaeli Peninsula (NW Turkey) provides one of the best exposed deep marine Upper Cretaceous-Palaeocene sectionsin north-western Anatolia. The biostratigraphic framework from three sections, namely Belen, Bulduk, and Toylar, in the southernpart of the Kocaeli Peninsula is established by means of planktonic foraminifera. A very rich planktonic foraminiferal assemblageanalysed both in thin sections and washed residues records a biozonation ranging from theContusotruncana contusa(CF6) Zone(Maastrichtian) to theGlobanomalina pseudomenardii(P4) Zone (Thanetian). Although a major part of the biozones in the studiedinterval is clearly defined, the upper three zones (CF1 3) of the latest Maastrichtian and the P0 and P1a zones of the earliest Palaeocenecannot be recognised. These unrecorded biozones are either completely missing or occurred within a very condensed interval in thestudied sections. A hardground layer characterised by oxidation and extensive bioturbation might indicate a possible biostratigraphicgap spanning the CF1 3 zones of the uppermost Maastrichtian in the Belen and Bulduk sections. In the Toylar section, on the otherhand, the CF1 3 zones still cannot be detected although a hardground layer is not observed. The biostratigraphic resolution across theCretaceous-Palaeogene (K-Pg) boundary in the studied sections cannot be improved due to the condensed and well-cemented pelagiccarbonates of the boundary interval.