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    Diatom communities, lithofacies characteristics and paleo environmental interpretation of Pliocene diatomite deposits in the lhlara-Selime plain (Aksaray, Central Anatolia, Turkey)
    (PERGAMON-ELSEVIER SCIENCE LTD, 2007) Gurel, Ali; Yildiz, Aysegul
    The present investigation uses palaeontological, sedimentological, mineralogical and chemical analyses of diatom-bearing lacustrine deposits to determine the palaeoenvironmental history of the Pliocene-age of the Ihlara-Selime plain in the western part of the Cappadocia Volcanic Province. The diatomite is composed of amorphous silica, opal, cristobalite, quartz, feldspar and montmorillonite. Chemical analyses show that diatomite is comprised of SiO2 85.05%, Al2O3 5.30%, Fe2O3 1.22%, CaO 0.12%, MgO 0.58%, Na2O 1.52% and K2O 0.22%. The high SiO2 content of Ihlara-Selime plain diatomite is highly conspicuous, as it could be predicted. Six horizons comprised of diatomite, palaeosols, limestone, massive conglomerate, massive calcrete, and trough-cross bedded sandstone describe the associated lithofacies (A-F). Twenty-five species were identified belonging to 20 diatom genera, from the analysis of 24 samples from three excavated sections of diatomite. The fossil diatom assemblages are mainly comprised of freshwater, epipelic, mesotrophic, mesosaprophic and alkaline forms. The flora is dominated by benthic species with very low abundance of planktonic species, indicating that the diatomite of the area under study was deposited in a shallow, silicate rich, alkaline and mesotrophic freshwater lake. Water levels, nutrient content, water temperature and alkalinity fluctuated through time. In addition, there was a difference between section one, and sections two and three locations in terms of the deposition conditions. (c) 2006 Elsevier Ltd. All rights reserved.
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    Diatom community and palaeoenvironmental properties of Karacaoren diatomite deposits (Nevsehir, Central Anatolia, Turkey)
    (Pergamon-Elsevier Science Ltd, 2017) Yildiz, Aysegul; Gurel, Ali; Dursun, Yusuf Gokhan
    The diatom community and palaeoenvironmental properties of volcano genetic diatomite deposits that outcrop in the Karacabren (Nevehir) area are described. Two stratigraphic sections were measured in the study area. One of these sections was measured in Quaternary lake units (K1), and the other in lacustrine sediments of the late Miocene -Pliocene Urgup Formation's Bayramhaoh Member (K2). According to stratigraphic and chemical characteristics of the sections, two distinct paleogeographic domains were determined in the study area. One of these, the shallow lacustrine to fluvial area (Quaternary) which is represented by an alternating sequence of diatomite, silt/mud, and tuffite. The other was the deeper lacustrine stage (late Miocene) which is represented by diatomites with some interbedded mud fades, chert and volcanics. From the diatomite samples of these sections, twenty-five species of 10 different diatom genera were identified. When evaluated together, the ecological properties and the distribution of numerical values of the determined diatom genera and species, showed that the study area's diatomite was generally deposited in shallow, high temperature, nutrient-rich water, where nitrogen and phosphorus were abundant and which was an alkaline (pH > 7) freshwater lake environment. Over time the pH value of the environment decreased (pH < 7), and the environment became acidic. (C) 2017 Elsevier Ltd. All rights reserved.
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    Pleistocene-Holocene calcareous nannofossil biostratigraphy of core samples from The Northeastern Sea of Marmara, Fenerbahce-Pendik, NW Turkey
    (PERGAMON-ELSEVIER SCIENCE LTD, 2006) Yildiz, Aysegul; Toker, Vedia
    Pseudoemiliana lacunosa, Gephyrocapsa oceanica and Emiliania huxleyi (Ionian) (Pleistocene-Holocene) calcareous nannoplankton zones were identified from 82 samples of 14 cores taken from 8 locations in the northeastern Sea of Marmara. The investigation indicates that the identified biozones have been alternated by tectonic activity in the 1, 5 and 6 core locations. The study area has been affected three times by tectonic activity during the Pleistocene-Holocene time interval. The first activity occured during the Early Pleistocene and the others during Holocene. (c) 2005 Elsevier Ltd. All rights reserved.