Multiple Orbitoides d’Orbigny lineages in the Maastrichtian? Data from the Central Sakarya Basin (Turkey) and Arabian Platform successions (Southeastern Turkey and Oman)

The standard reconstruction of species of Orbitoides d'Orbigny into a single lineage during the late Santonian to the end of the Maastrichtian is based upon morphometric data from Western Europe. An irreversible increase in the size of the embryonic apparatus, and the formation of a greater number of epi-embryonic chamberlets (EPC) with time, is regarded as the main evolutionary trends used in species discrimination. However, data from Maastrichtian Orbitoides assemblages from Central Turkey and the Arabian Platform margin (Southeastern Turkey and Oman) are not consistent with this record. The Maastrichtian Besni Formation of the Arabian Platform margin in Southeastern Turkey yields invariably biconvex specimens, with small, tri- to quadrilocular embryons and a small number of EPC, comparable to late Campanian Orbitoides medius (d'Archiac). The upper Maastrichtian Tarakli Formation from the Sakarya Basin of Central Turkey contains two distinct, yet closely associated forms of Orbitoides, easily differentiated by both external and internal features. Flat to biconcave specimens possess a small, tri- to quadrilocular embryonic apparatus of Orbitoides medius-type and a small number of EPC, whereas biconvex specimens possess a large, predominantly bilocular embryonic apparatus, and were assigned to Orbitoides ex. interc. gruenbachensis Papp-apiculatus Schlumberger based on morphometry. The flat to biconcave specimens belong to a long overlooked species Orbitoides pamiri Meric, originally described from the late Maastrichtian of the Tauride Mountains in SW Turkey. This species is herein interpreted to be an offshoot from the main Orbitoides lineage during the Maastrichtian, as are forms that we term Orbitoides 'medius', since they recall this species, yet are younger than normal occurrence with the accepted morphometrically defined lineage. The consistent correlation between the external and internal test features in O. pamiri implies that the shape of the test is not an ecophenotypic variation, but appears to be biologically controlled. We, therefore, postulate that more than one lineage of Orbitoides exists during the Maastrichtian, with a lineage that includes O. 'medius' and O. pamiri displaying retrograde evolutionary features

Stratigraphy and Late Oligocene-Early Miocene Deformation of the Southwestern Part of the Thrace Basin

Thesis (M.Sc.) -- İstanbul Technical University, Eurasia Institute of Earth Sciences, Yüksek LisansTez (eng) -- İstanbul Teknik Üniversitesi, Avrasya Yer Bilimleri Enstitüsü, Yüksek LisansKuzeybatı Türkiye'de bulunan Trakya Havzası, Eosen-Oligosen yaşta çökel bir alanı temsil etmektedir. Havzada Orta-Geç Eosen döneminde başlayan sedimentasyon, Geç Oligosen döneminde sonlanmış, bölge yükselerek aşınmıştır. Bu yükselim ve aşınma döneminde Trakya Havzası'nda birçok kıvrım gelişmiştir. Bu yüksek lisans tezi çalışmasında, Trakya Havzası'nın güneybatı kesiminin Eosen-Oligosen stratigrafisi ve Geç Oligosen-Erken Miyosen deformasyonunun yapısal özellikleri incelenmiştir. Bu kapsamda araştırma yapmak üzere geniş bir antiklinal olan Korudağı bölgesi seçilmiş, klasik saha jeoloji yöntemi başta olmak üzere, LA-ICP-MS zirkon jeokronolojisi ve biyostratigrafi gibi yöntemler kullanılarak kaya stratigrafi birimlerinin yaşları tespit edilmiştir. Korudağı bölgesinin temel kayalarını Eosen öncesi yaşta metamorfik birimler oluşturur. Yunanistan'daki Rodop Çevresi Kuşağı'na dahil edilen metamorfik temel kayaları; fillat, sleyt ve rekristalize kireçtaşlarından meydana gelmektedir. Temel kayaları üzerinde uyumsuzlukla baskın olarak konglomeralardan ve eser miktarda kumtaşlarından oluşan Fıçıtepe Formasyonu bulunur. Fıçıtepe Formasyonu üzerinde sığ denizel platform karbonatlarından yapılı Orta-Üst Eosen yaşlı Soğucak Formasyonu yer almaktadır. Soğucak Formasyonu'nun üst kesiminden ölçülen bir adet kesit Korudağı bölgesindeki transgresyonun Geç Priyaboniyen (SBZ 20) döneminde gerçekleştiğini göstermiştir. Soğucak Formasyonu üzerinde uyumlu olarak, kalın bir yakınsak türbidit istifinden meydana gelen Keşan Formasyonu bulunmaktadır. Keşan Formasyonu içerisinden derlenen bir adet tüf örneğinden yapılan LA-ICP-MS zirkon yaşı Erken Oligosen (31.63±0.37 My) yaş vermiştir. Keşan Formasyonu içerisinde bu çalışma kapsamında üye mertebesinde tanımlanmış olan Çeltik Kireçtaşı bulunur. Baskın olarak pelajik kireçtaşları, az miktarda kalsitürbidit ve marnlardan oluşan Çeltik Kireçtaşı Üyesi'nin yaşı yapılan paleontolojik çalışmalar sonucu Üst Eosen (P15-P16/P17) olarak belirlenmiştir. Korudağı bölgesinde Orta-Üst Eosen döneminde başlayan çökelim dönemi Geç Oligosen-Erken Miyosen döneminde gerçekleşen kıvrımlanma ve yükselim sonucu bitmiş, Eosen-Oligosen birimleri uyumsuzlukla Neojen yaşlı karasal çökellerden yapılı Mahmutköy Neojen İstifi ve Mahmutköy Bazaltı tarafından örtülmüştür. Geniş bir antiklinali temsil eden Korudağı'nın oluştuğu döneme karşılık gelen bu deformasyonun yapısal özelliklerini belirlemek amacıyla bölgedeki tabaka duruşları incelenmiştir. Korudağı, yukarı doğru bakan, dik kıvrım eksenli, ekseni yatay dalımlı antiklinal bir yapıyı temsil etmektedir. Kıvrım ekseninin gidişi K65ºD yönlüdür. Korudağı antiklinalinin güney kanadı dikçe eğimlidir ve bir kör bindirme fayı sonucu gelişmiştir. Korudağı antiklinali yapı ve yaş bakımından Trakya Havzası'nın güney kesimindeki kıvrımlara benzerlik sunmaktadır. Bölgedeki kıvrım eksenlerinin gidişi, asimetrik kıvrım geometrileri ve bölgesel Neojen uyumsuzluğu, Korudağı antiklinali ve ilişkili kıvrımların, Geç Oligosen-Erken Miyosen döneminde tabakalanmaya paralel kısalma sonucu oluşmuş büklümlü kıvrımları temsil ettiğini göstermektedir.Thrace Basin represents an Eocene-Oligocene aged depocenter in northwest Turkey. Sedimentation in the basin which began in the Middle-Late Eocene was ceased during the Late Oligocene and the region was uplifted and eroded since then. Many folds have formed during this uplifting and erosion period in the Thrace Basin. In this MSc thesis, Eocene-Oligocene stratigraphy and the structural features of the Late Oligocene-Early Miocene deformation in the southwestern part of the Thrace Basin were investigated. In this context, the Korudağı region which is a large anticline was selected for the purpose of study, age of the lithostratigraphical units were established using LA-ICP-MS zircon geochronology and biostratigraphy, particularly classical field geological methods. Pre-Eocene metamorphic units form the basement of the Korudağı region. The metamorphic basement rocks which belong to Circum Rhodope Belt in Greece consist of phyllites, slates and recrystallized limestones. Conglomerates and sandstones of the Fıçıtepe Formation unconformably overlie the metamorphic basement rocks. The Fıçıtepe Formation is overlain by the Soğucak Formation. The middle-upper Eocene aged Soğucak Formation is made up of shallow marine platform carbonates. A section measured from the upper part of the Soğucak Formation has shown that the transgression in the Korudağı region occurred during the Late Priabonian (Shallow Benthic Zone 20). The Soğucak Formation is conformably overlain by the thick proximal turbidites of the Keşan Formation. LA-ICP-MS zircon ages of the one tuff sample collected from the Keşan Formation gave Early Oligocene (31.63±0.37 Ma) age. The Çeltik Limestone which is defined as a member of the Keşan Formation in this study, predominantly consists of pelagic limestones, calciturbidites and subordinate marls. According to the paleontological studies, age of the Çeltik Limestone Member is Upper Eocene (P15-P16/P17). Sedimentation that began during the Middle-Late Eocene in the Thrace Basin was ceased during the Late Oligocene-Early Miocene as a result of folding and uplift and the Eocene-Oligocene units were unconformably overlain by the sequence which is made up of continental units and the Mahmutköy basalt. General strike and dip of the bedding planes in the region were investigated in order to understand the structural features of the deformation which corresponds to a period resulted in the formation of the Korudağı anticline. The Korudağı is an upward facing, upright and horizontally plunged anticline. Direction of the fold axis is N65ºE. Steep southern limb of the Korudağı is induced by a blind thrust fault. The Korudağı anticline is similar to that of the folds located in the southern part of the Thrace Basin in terms of the age and structure. Direction of the fold axis, asymmetrical fold geometry and regional Neogene unconformity indicate that the Korudağı anticline and related folds are buckle folds formed by layer-parallel shortening during the Late Oligocene-Early Miocene.Yüksek LisansM.Sc

Late Oligocene—Early Miocene shortening in the Thrace Basin, northern Aegean

Late Cenozoic was a period of large-scale extension in the Aegean. The extension is mainly recorded in the metamorphic core complexes with little data from the sedimentary sequences. The exception is the Thrace Basin in the northern Aegean, which has a continuous record of Middle Eocene to Oligocene marine sedimentation. In the Thrace Basin, the Late Oligocene–Early Miocene was characterized by north-northwest (N25°W) shortening leading to the termination of sedimentation and formation of large-scale folds. We studied the stratigraphy and structure of one of these folds, the Korudağ anticline. The Korudağ anticline has formed in the uppermost Eocene–Lower Oligocene siliciclastic turbidites with Early Oligocene (31.6 Ma zircon U–Pb age) acidic tuff beds. The turbidites are underlain by a thin sequence of Upper Eocene pelagic limestone. The Korudağ anticline is an east-northeast (N65°E) trending fault-propagation fold, 9 km wide and 22 km long and with a subhorizontal fold axis. It is asymmetric with shallowly-dipping northern and steeply-dipping southern limbs. Its geometry indicates about 1 km of shortening in a N25°W direction. The folded strata are unconformably overlain by Middle Miocene continental sandstones, which constrain the age of folding. The Korudağ anticline and other large folds in the Thrace Basin predate the inception of the North Anatolian Fault (NAF) by at least 12 myr. The Late Oligocene–Early Miocene (28–17 Ma) shortening in the Thrace Basin and elsewhere in the Balkans forms an interlude between two extensional periods, and is probably linked to changes in the subduction dynamics along the Hellenic trench.TÜBİTAKİTÜ-BAPTÜBAFreie Universität Berlin (1008

Late Oligocene–Early Miocene shortening in the Thrace Basin, northern Aegean

Late Cenozoic was a period of large-scale extension in the Aegean. The extension is mainly recorded in the metamorphic core complexes with little data from the sedimentary sequences. The exception is the Thrace Basin in the northern Aegean, which has a continuous record of Middle Eocene to Oligocene marine sedimentation. In the Thrace Basin, the Late Oligocene–Early Miocene was characterized by north-northwest (N25°W) shortening leading to the termination of sedimentation and formation of large-scale folds. We studied the stratigraphy and structure of one of these folds, the Korudağ anticline. The Korudağ anticline has formed in the uppermost Eocene–Lower Oligocene siliciclastic turbidites with Early Oligocene (31.6 Ma zircon U–Pb age) acidic tuff beds. The turbidites are underlain by a thin sequence of Upper Eocene pelagic limestone. The Korudağ anticline is an east-northeast (N65°E) trending fault-propagation fold, 9 km wide and 22 km long and with a subhorizontal fold axis. It is asymmetric with shallowly-dipping northern and steeply-dipping southern limbs. Its geometry indicates about 1 km of shortening in a N25°W direction. The folded strata are unconformably overlain by Middle Miocene continental sandstones, which constrain the age of folding. The Korudağ anticline and other large folds in the Thrace Basin predate the inception of the North Anatolian Fault (NAF) by at least 12 myr. The Late Oligocene–Early Miocene (28–17 Ma) shortening in the Thrace Basin and elsewhere in the Balkans forms an interlude between two extensional periods, and is probably linked to changes in the subduction dynamics along the Hellenic trench