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    Biostratigraphic and isotopic data on the Coreklik Member of the Hekimhan Formation (Campanian-Maastrichtian) of SE Turkey and their palaeoenvironmental significance
    (ACADEMIC PRESS LTD, 1999) Yildiz, A; Ozdemir, Z
    The Coreklik 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 the Globotruncana ventricosa, Globotruncanita calcarata (Campanian), Globotruncanella havanensis, Globotruncana aegyptiaca, and Gansserina gansseri (Maastrichtian) planktic foraminiferal zones were recognised. Thirty-two calcareous nannoplankton species and the Ceratolithoides 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), and Lithraphidites 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 delta(18)O parts per thousand (PDB) and delta(13)C parts per thousand (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. (C) 1999 Academic Press.
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    Biostratigraphic and palaeoecologic study of the early Maastrichtian-Paleocene sediments in Kalecik region (Ankara-Turkey)
    (KING FAHD UNIV PETROLEUM MINERALS, 1999) Yildiz, A; Karahasan, G; Demircan, H; Toker, V
    In this study, the Gansserina gansseri (early Maastrichtian), Morozovella pseudobulloides, Morozovella trinidadensis (Danian), Morozovella angulata (Danian-Thanetian), Planorotalites pseudomenardii, Morozovella velascoensis (Thanetian) planktic foraminiferal zones and Arkhangelskiella cymbiformis (CC-25) (early Maastrichtian), Markalius inversus (NP-1), Cruciplacolithus tenuis (NP-2), Chiasmolithus danicus (NP-3) (Danian), Ellipsolithus macellus (NP-4), Fasciculithus tympaniformis (NP-5), and Heliolithus kleinpellii (NP-6) (Thanetian), calcareous nannoplankton zones were recognized from samples collected from the upper level of the Samanhk Formation and from the bottom to the top of the Dizilitaslar Formation. These units represent the early Maastrichtian-Paleocene interval. They were deposited in the turbidite facies of the southeast Kalecik region. On the basis of trace fossil studies Thalassinoides isp. (shallow marine) was identified in the upper level of the Samanlik Formation, and Helminthopsis isp. (deep marine), and Ophiomorpha isp. (shallow marine) were recognized in the bottom and middle levels of the Dizilitaslar Formation. Results from studies of trace fossils, analysis of sedimentary composition, distribution of the numerical abundance of planktic, benthic foraminifera, and calcareous nannoplankton show that the upper levels of the Samanlik and Dizilitaslar formations were deposited with the characteristic proximal facies, whereas the lower and middle levels of Dizilitaslar Formation represent the proximal and intermediate facies of a submarine fan. Lower Maastrichtian, Upper Danian and Thanetian were developed during a regressive period while the lower and middle Danian reflect alternating transgressive and regressive events. Comparing palaeotemperature and palaeosalinity values which are calculated from delta(18)O parts per thousand and delta(13)C parts per thousand (PDB) from planktic foraminifera tests and percentage abundance as well as the diversity of temperature-sensitive calcareous nannoplankton groups, indicates that during the early Maastrichtian, the palaeotemperature and palaeosalinity of sea-surface water was relatively lower than during the Paleocene. Palaeotemperature and palaeosalinity values started to increase from the early Danian onwards.
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    Distribution of recent calcareous nannofossils in bottom sediments from Gokceada-Bozcaada-Dardanelles triangle
    (KING FAHD UNIV PETROLEUM MINERALS, 2001) Yildiz, A
    Twenty-nine species of 12 calcareous nannoplankton genera have been recognized in an investigation of 100 surface samples from Gokceada-Bozcaada-Dardanelles triangle in the northeastern Aegean Sea. Emiliana huxleyi (Lohmann) is the dominant species; the diversity of nannofossils increases proportionally with water depth, salinity, and temperature from the Dardanelles to the Aegean Sea. In the studied area, subtropical-warm species exceed those of the subtropical-cool regime. Coccolithus pelagicus (Wallich) and Gephyrocapsa caribbeanica Boudreaux and Hay, which represent the subtropical-cool waters, display an increase in abundances at the exit of Dardanelles. In contrast, Gephyrocapsa oceanica Kamptner and Syracosphaera pulchra Lohmann, which represent the subtropical-warm waters, display an increase in abundance away from the exit of Dardanelles to the Aegean Sea.
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    Palaeontological, diagenetic and facies characteristics of Cretaceous/Paleogene boundary sediments in the Ordu, Yavuzlu and Uzunisa areas, Eastern Pontides, NE Turkey
    (ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD, 2005) Yildiz, A; Gurel, A
    The region discussed in this paper is located in the eastern part of the Pontide tectonic unit in north-east Turkey. From north to south it comprises the Ordu, Yavuzlu and Uzunisa areas, which form part of the Pontide fore-are basin. The region shows different facies developments through the Upper Cretaceous to the Eocene, and the K/Pg boundary section is represented by limestones, sandstones, and glauconitic sandstones. While investigating the palaeontological, diagenetic and facies characteristics of the boundary sediments, it was observed that the Maastrichtian age is represented by thicker successions than the Paleocene in the northern and southern parts of the study area. By contrast, in the centre, the Palcocene epoch is represented by a thicker sequence. It was also determined that the area has become deeper from north to south, owing to rifting during the Maastrichtian-Paleocene and uplift to the north. © 2005 Elsevier Ltd. All rights reserved.