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

The Coreklik Member of the Hekimhan Formation crops out in the Hekimhan (Ma latya) region of SE Turkey. It includes beds that are rich in planktic and benthic foraminifera, and in calcareous nannoplankton. Eighty-eight rock sa mples, considered to be representative of the stratigraphic section, were e xamined. Seventeen species of planktic foraminifera and the Globotruncana v entricosa, Globotruncanita calcarata (Campanian), Globotruncanella havanens is, Globotruncana aegyptiaca, and Gansserina gansseri (Maastrichtian) plank tic foraminiferal zones were recognised. Thirty-two calcareous nannoplankto n species and the Ceratolithoides aculeus (CC-20), Quadrum sissinghii (CC-2 1), Quadrum trifidum (CC-22) (Campanian), Tranolithus phacelosus (CC-23) (L ate Campanian-Early Maastrichtian), Reinhardites levis (CC-24), Arkhangelsk iella cymbiformis (CC-25), and Lithraphidites quadratus (Early-Late Maastri chtian) 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 cal culated from delta(18)O parts per thousand (PDB) and delta(13)C parts per t housand (PDB) isotope Values obtained from globotruncanid tests, and the ab undance and diversity of temperature-sensitive calcareous nannoplankton gro ups allowed the following conclusions to be drawn. (1) Maximum phytoplankto n 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 M aastrichtian; and (3) sea-surface temperature values were stable through th e Campanian-Early Maastrichtian but began to fall slowly and intermittently from the end of Early Maastrichtian, reaching minimum values during the La te Maastrichtian. (C) 1999 Academic Press.