First data on the expression of the Campanian-Maastrichtian boundary event in Bulgaria: Calcareous nannofossil and carbon isotope record

Abstract

We present the first combined calcareous nannofossil and stable isotope data (δ13C and δ18O) from the Kladorub section, NW Bulgaria, to study the local expression of the globally recognized Campanian-Maastrichtian Boundary Event (CMBE). Calcareous nannofossil study proves the completeness of the sedimentary succession, with zones UC15eTPthrough UC20dTPevidenced. The isotope data, derived from benthic foraminifera, show that the carbon isotope excursion (CIE) curve displays the well-known superimposed detailed structure of five small positive peaks (CMBE1 to CMBE5). The CMBE-CIE in the Bulgarian locality is characterized by a significant magnitude of 1.97‰, reaching its maximum value in CMBE1 (1.90‰), while the minimum value (- 0.07‰) is in CMBE2. The Campanian-Maastrichtian boundary, drawn at the LO of the nannofossil species Uniplanarius trifidus, lies at the top of CMBE3. Two more neighbouring events, bracketing the CMBE - namely the Late Campanian (LCE) and the Middle Maastrichtian events (MME), are possibly also recorded in Bulgaria.