Biostratigraphic and isotopic data on the Çöreklik Member of the Hekimhan Formation (Campanian-Maastrichtian) of SE Turkey and their palaeoenvironmental significance

Abstract

The Çöreklik Member of the Hekimhan Formation crops out in the Hekimhan (Malatya) region of SE Turkey. It includes beds that are rich in planktic and benthic foraminifera, and in calcareous nannoplankton. Eighty-eight rock samples, considered to be representative of the stratigraphic section, were examined. Seventeen species of planktic foraminifera and theGlobotruncana ventricosa,Globotruncanita calcarata(Campanian),Globotruncanella havanensis,Globotruncana aegyptiaca, andGansserina gansseri(Maastrichtian) planktic foraminiferal zones were recognised. Thirty-two calcareous nannoplankton species and theCeratolithoides aculeus(CC-20),Quadrum sissinghii(CC-21),Quadrum trifidum(CC-22) (Campanian),Tranolithus phacelosus(CC-23) (Late Campanian-Early Maastrichtian),Reinhardites levis(CC-24),Arkhangelskiella cymbiformis(CC-25), andLithraphidites quadratus(Early-Late Maastrichtian) zones were identified. Analyses of the sediments, the distribution of planktic and benthic foraminifera and calcareous nannoplankton, the sea-surface palaeotemperature values and palaeosalinity levels respectively calculated from δ18O‰ (PDB) andδ13C‰ (PDB) isotope values obtained from globotruncanid tests, and the abundance and diversity of temperature-sensitive calcareous nannoplankton groups allowed the following conclusions to be drawn. (1) Maximum phytoplankton abundances and highest sea level were reached during the Early Campanian; (2) both the numbers of phytoplankton and the sea level began to fall from the Late Campanian onwards, reaching their lowest levels during the Late Maastrichtian; and (3) sea-surface temperature values were stable through the Campanian-Early Maastrichtian but began to fall slowly and intermittently from the end of Early Maastrichtian, reaching minimum values during the Late Maastrichtian.