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    Biostratigraphic and palaeoecologic study of the early Maastrichtian-Paleocene sediments in Kalecik region (Ankara-Turkey)
    (King Fahd University of Petroleum and Minerals, 1999) Yıldız, Ayşegül; Karahasan, Güher; Demircan, Huriye; Toker, Vedia
    In this study, the Gansserina gansseri (early Maastrichtian), Morozovella pseudobuUoides, Morozovella trinidadensis (Danian), Morozovella angulata (DanianThanetian), Planorotalites pseudomenardii, Morozovella velascoensis (Thanetian) planktic foraminiferal zones and Arkhangelskiella cymbiformis (CC-2S) (early Maastrichtian), Markalius inversus (NP-l), Cruciplacolithus tenuis (NP-2), Chiasmolithus danicus (NP-3) (Danian), Ellipsolithus macellus (NP-4), Fasciculithus tympaniformis (NP-S) , and Heliolithus kleinpellii (NP-6) (Thanetian), calcareous nannoplankton zones were recognized from samples collected from the upper level ofthe Samanhk Formation and from the bottom to the top of the Dizi1i~lar Formation. These units represent the early MaastrichtianPaleocene 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 Samanhk Formation, and Helminthopsis isp. (deep marine), and Ophiomorpha isp. (shallow marine) were recognized in the bottom and middle levels of the Dizili~lar 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 Samanhk and Dizili~lar formations were deposited with the characteristic proximal facies, whereas the lower and middle levels of Dizili~lar 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 ()lBO %0 and ()13C %0 (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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    Biostratigraphy and paleoenvironmental interpretation of the Middle Miocene submarine fan in the Adana Basin (southern Turkey)
    (Walter de Gruyter, 2007) Demircan, Huriye; Yıldız, Ayşegül
    The turbiditic Cingöz Formation of the Karaisah-Çatalan-E?ner region, Adana Basin, southern Turkey was studied in detail in two sections based on planktonic foraminifers, calcareous nannofossils and trace fossils. The Middle Miocene (Langhian-Serravalian) age of the sediments is supported by the Praeorbulina glomerosa curva and Orbulina suturalis planktonic foraminiferal Zones and by standard nannoplankton Zones NN5 Sphenolithus heteromorphus and NN6 Discoaster exilis. Moreover, 24 ichnotaxa were identified and attributed to the Skolithos-Cruziana, mixed (Skolithos-Cruziana and Nereites), and Nereites ichnofacies. Fossil assemblages indicate eutrophic and oligotrophic conditions. In the Langhian, the distribution and percentage abundances of temperature sensitive planktonic taxa including Globigerina falconensis reflect temperate to cold surface waters in the depositional area of the western and eastern fans of Cingöz Formation. In Serravalian, higher numbers of warm-water prefering taxa indicate the rise in temperature in the western fan.
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    Chronology of subduction and collision along the İzmir-Ankara suture in Western Anatolia: records from the Central Sakarya Basin
    (Taylor & Francis Online, 2019) Ocakoğlu, Faruk; Hakyemez, Aynur; Açıkalın, Sanem; Altıner, Sevinç Özkan; Büyükmeriç, Yeşim; Licht, Alexis; Demircan, Huriye; Şafak, Ümit; Yıldız, Ayşegül; Yılmaz, İsmail Ömer; Wagreich, Michael; Campbell, Clay
    Western Anatolia is a complex assemblage of terranes, including the Sakarya Terrane and the Tauride-Anatolide Platform that collided during the late Cretaceous and Palaeogene (80–25 Ma) after the closure of the Izmir-Ankara Ocean. Determining the precise timing at which this ocean closed is particularly important to test kinematic reconstructions and geodynamic models of the Mediterranean region, and the chronology of suturing and its mechanisms remain controversial. Here, we document the Cretaceous-Eocene sedimentary history of the Central Sakarya Basin, along the northern margin of the Neotethys Ocean, via various approaches including biostratigraphy, geochronology, and sedimentology. Two high-resolution sections from the Central Sakarya Basin show that pelagic carbonate sedimentation shifted to rapid siliciclastic deposition in the early Campanian (~ 79.6 Ma), interpreted to be a result of the build-up of the accretionary prism at the southern margin of the Sakarya Terrane. Rapid onset of deltaic progradation and an increase in accumulation rates in the late Danian (~ 61 Ma), as well as a local angular unconformity are attributed to the onset of collision between the Sakarya Terrane and the TaurideAnatolide Platform. Thus, our results indicate that though deformation of the subduction margin in Western Anatolia started as early as the Campanian, the closure of the İzmir-Ankara Ocean was only achieved by the early Palaeocene.
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    Öğe
    Kalecik (Ankara) güneydoğusu alt Maastrichtiyen-Paleosen biyostratigrafisi ve paleoekolojisi
    (2000) Yıldız, Ayşegül; Karahasan, Güher; Demircan, Huriye; Toker, Vedia
    Kalecik (Ankara) güneydoğusunda fliş fasiyesinde çökelmiş, yörede Alt Maastrihtiyen ve Paleosen' i temsil eden Samanlık formasyonunun üst seviyeleri ile Dizilitaşlar formasyonunun tamamından derlenen örneklerden Gansserina gansseri (Alt Maastrihtiyen), Morozovella pseudobulloides, Morozovella trinidadensis (Daniyen), Morozovella angulata (Daniyen-Tanesiyen), Planorotalites pseudomenardii, Morozovella velascoensis (Tanesiyen) planktik foraminifer zonları ile Arkhangelskiella cymbiformis (CC-25) (Alt Maastrihtiyen), Markalius inversus (NP-1), Cruciplacolithus tenuis (NP-2), Chiasmolithus danicus (NP-3) (Daniyen), Ellipsolithus macellus (NP-4), Fasciculithus tympaniformis (NP-5), Heliolithus kleinpellii (NP-6) (Tanesiyen) kalkerli nannoplankton zonları tanımlanmıştır, iz fosil çalışmaları ile Samanlık formasyonunun üst seviyelerinde Thalassinoides isp. (sığ deniz), Dizilitaşlar formasyonunun taban ve orta seviyelerinde ise Helminthopsis isp. (derin deniz), Ophiomorpha isp. (sığ deniz) türleri gözlenmiştir. iz fosil toplulukları, sediman kompozisyon analizi sonuçları, planktik, bentik foraminifer ve kalkerli nannoplankton sayısal bolluk dağılımları birlikte değerlendirilerek, Erken Maastrihtiyen-Paleosen boyunca yörede deniz seviyesinin sabit olmadığı belirlenmiştir. Elde edilen verilere göre, Samanlık formasyonunun üst seviyeleri Erken Maastrihtiyen' de denizaltı yelpazesinin yakınsak kesimlerinde çökelmiştir. Dizilitaşlar formasyonunun taban ve orta seviyeleri Alt-Orta Daniyen' de denizaltı yelpazesinin ortaç ve yakınsak kesimlerinde, üst seviyeleri ise Üst Daniyen-Tanesiyen boyunca yakınsak kesimlerinde depolanmıştır. Planktik foraminifer kavkılarından elde edilen ?18O0/? ve ?13O0/?(PDB) izotop değerleri ile hesaplanan paleosıcaklık ve paleotuzluluk miktarları, ısıya karşı duyarlı olan kalkerli nannoplankton gruplarının yüzde bolluk dağılımları ile karşılaştırıldığında Erken Maastrihtiyen boyunca deniz yüzey suyu sıcaklığı ve tuzluluğunun Paleosen' e oranla düşük olduğu, Paleosen' de ise Daniyen' in başından itibaren arttığı belirlenmiştir.
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    Öğe
    Paleoenvironmental interpretation and findings of Pliocene-Pleistocene nannoplankton, planktic foraminifera, trace fossil in the Mut Basin [Mut Havzasi Pliyosen-Pleyistosen nannoplankton, planktik foraminifera, iz fosil bulgulari ve paleoortam yorumu]
    (2003) Yildiz, Ayşegül L.; Toker, Vedia; Demircan, Huriye; Sevim, Serkan
    In this study, carried out in the Mut Basin, Reticulofenestra pseudoumbilica (Zanklian), Dictyococcites productus (Gelasian), Pseudoemiliana lacunosa (zones), Calcidiscus macintyrei, Helicosphaera sellii and Small Gephyrocapsa (Sub zones) (Gelasian-Kalabrian) nannoplankton zones with Globorotalia puncticulata (Zanklian-Piasenzian), Globorotalia inflata (zones) (Piasenzian-Gelasian) and Globigerina calida calida (Sub Zone) (Kalabrian) planktic foraminiferal zones were recognized in 72 samples collected from 3 measured stratigraphic sections at the upper levels of marginal deposits of the Köselerli formation. Based on these biozones, it is found that, age of the Köselerli formation has been extending to early Pleistocene (Kalabrian) at its marginal deposits. In the previous studies, the age of basin deposits of Köselerli formation has been determined as late Burdigalian-Langhian.