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Upper Permian (Changxingian) Radiolarian Cherts within the Clastic Successions of the "Karakaya Complex" in NW Anatolia
No full textThe arkosic sandstones with olistostromes within the "Karakaya Complex" in NW Anatolia to the south of Geyve include a thin layer of green chert with radiolaria. Based on the composition of Albaillellids, the radiolarian assemblage corresponds to the Neoalbaillella ornithoformisassemblage, and its age is assigned to the Changxingian (Late Permian). This is the first finding of synsedimentary radiolarian cherts within the Karakaya units and the indication of latest Permian rifting of the Karakaya basin within the Midian carbonate platform and its pre-Permian basement in the Sakarya Composite Terrane.Published201-213ope
Upper Permian (Changxingian) Radiolarian Cherts within the Clastic Successions of the "Karakaya Complex" in NW Anatolia
No full textThe arkosic sandstones with olistostromes within the "Karakaya Complex" in NW Anatolia to the south of Geyve include a thin layer of green chert with radiolaria. Based on the composition of Albaillellids, the radiolarian assemblage corresponds to the Neoalbaillella ornithoformisassemblage, and its age is assigned to the Changxingian (Late Permian). This is the first finding of synsedimentary radiolarian cherts within the Karakaya units and the indication of latest Permian rifting of the Karakaya basin within the Midian carbonate platform and its pre-Permian basement in the Sakarya Composite Terrane.Published201-213ope
Early Paleozoic evolution of the NW Gondwanaland: data from southern Turkey and surrounding regions
No full textThe Lower Paleozoic assemblages in the E. Meditterranean comprise a Southern (Tauride-Anatolide,SE Anatolia and Central Iranian terranes) and a Northern (Carpathian-Balkan, Istanbul, Zonguldak and the Main Range terranes) Zone. A detailed stratigrapic account is given for these terranes for the Early Paleozoic and their paleogeographical settings are discussed to evaluate the Early Paleozoic geodynamic interpretation of this critical area between Gondwana-Perigondwana and Laurussia..Published315-323JCR Journalope
The Ayli Dağ ophiolite sequence (central-northern Turkey): a fragment of Middle Jurassic oceanic lithosphere within the Intra-Pontide suture zone
No full textThe Ayli Dağ ophiolites occur as an independent tectonic unit within the Intra-Pontide suture zone, central-northern Turkey. They crop out, together with the other units of the Intra-Pontide suture zone, at the top of the Late Cretaceous-Middle Paleocene foredeep sediments of the Sakarya Terrane. The Ayli Dağ ophiolites sequence include in its lower part a mantle sequence consisting of not less than 2-3 km-thick peridotites, topped by 500-600 m-thick layered gabbros with alternating, dm- to m-thick layers of spinel-bearing dunites, melatroctolites, troctolites, ol-gabbros and leucogabbros. The gabbro sequence is overlain
by a sheeted dyke complex, that shows a transition to 100-200 m-thick massive basaltic lava flows followed by 600-800 m-thick massive and pillow lavas and breccias alternating with ophiolite-bearing arenites and cherts. Geochemical evaluation of the mafic lavas and dykes reveals three distinct chemical groups that reflect melt generation within an intra-oceanic subduction system. Among these, the first group shows island-arc tholeiite (IAT)-like features, showing very-depleted characteristics (very high Zr/Nb, low Zr/Y and Nb/Y) ratios coupled with light rare-earth (LREE)-depleted chondrite-normalized patterns. The second group is more akin to back-arc basin basalts (BABB); it displays normal mid-ocean ridge basalt (N-MORB)-like high-field strength element (HFSE) distribution except for depletion in Nb, and flat REE patterns. The third group is somewhat similar to the second one, displaying BABB-like characteristics, but it is more enriched in terms of absolute trace element abundances. The radiolarian cherts sampled from the top of the pillow lavas yielded less-diverse but characteristic radiolarian assemblages indicating the middle Bathonian to early Callovian ages.
The Ayli Dağ Ophiolite is the first finding of back-arc type oceanic lithosphere in the Intra-Pontide suture zone. Together with previous data obtained from basalts in the mélange from the Intra-Pontide suture zone, this finding represents a proof that an intra-oceanic subduction within the Intra-Pontide oceanic basin occurred in the Middle Jurassic time
Stratigraphical, paleontological and structural features of the Tarakli Flysch in the Boyali area: evidences for the tectonic history of the Intrapontide suture zone
No full textPaleothetys and Neothetys suture zones in northern Turkey:evidences from Daday-Arac-Kursunlu geotraverse
No full textThe Taraklı flysch in the Boyalı area (Sakarya terrane, northern Turkey): implications for the tectonic history of the Intrapontide suture zone
Full text linkIn the Boyali area, northern Turkey, the tectonic units of the İstanbul-Zonguldak Terrane and the IntraPontide suture zone are thrust over the deposits at the top of the Sakarya Terrane, known as Tarakli Flysch. It consists of Early Maastrichtian-Middle Paleocene turbidite and mass-gravity deposits, whose source mainly corresponds to the İstanbul-Zonguldak Terrane, and, with a lesser extent, to the IntraPontide suture zone. These deposits were sedimented in a foredeep basin developed during the convergence between Sakarya and Eurasian continental microplates. In the Late Paleocene-Early Eocene time span, the Tarakli Flysch was deformed (D1 phase) during the closure of the foredeep basin. In the Miocene time, the strike-slip tectonics (D2 phase) related to the North-Anatolian fault produced further deformations of the Tarakli Flysch
Intrapontide suture zone in northern Turkey: evidences from Daday-Arac-Kursunlu geotraverse
No full textThe Arkot Dağ Mélange in Araç area, central Turkey: Evidence of its origin within the geodynamic evolution of the Intra-Pontide suture zone.
No full textIn northern Turkey, the IntraPontide suture zone is represented by an east-west trending belt of deformed and/or metamorphic units located at the boundary between the Istanbul-Zonguldak Terrane to the north and the Sakarya Terrane to the south. These units can be regarded as issued from the IntraPontide domain, whose geodynamic history is still matter of debate. Along the Akpinar-Araç-Bayramoren geotraverse, located in central Turkey, an ophiolite-bearing mélange known as Arkot Dağ Mélange, is well exposed along the IntraPontide suture zone. The Arkot Dağ Mélange, that plays a key role in the interpretation of the geodynamic history of the IntraPontide domain, can be described as a Late Santonian chaotic sedimentary deposits consisting of an up to 1000 m thick succession of slide-blocks, with different size and lithology, enclosed in a sedimentary matrix consisting of shales, coarse-grained arenites, pebbly-mudstones and pebbly-sandstones. The slide-blocks, from few meters to some hectometers in size, are represented by metamorphic rocks (mainly micaschists and gneisses), by ophiolites (peridotites, gabbros, IAT and BABB basalts and cherts) and by sedimentary rocks (cherts, neritic and pelagic limestones, marly-limestones and ophiolite-bearing turbidites). The youngest age among the slide-blocks has been provided by the ophiolite-bearing turbidites where a late Coniacian nannofossil assemblage has been found. The cherts have provided a wide range of ages from Middle Trias to Late Cretaceous, whereas the fossils found in the limestones indicate Late Jurassic to Early Cretaceous ages. The matrix of the Arkot Dağ Mélange, even if unaffected by metamorphism, shows deformations represented by multiple, m-thick cataclastic shear zones, recognized at the boundaries of the mélange slices or inside them. According to its features, the source area of the Arkot Dağ Mélange was probably represented by a continental and oceanic thrust sheets emplaced in the Late Cretaceous onto a continental margin. The data collected from the different slide-blocks suggest that the IntraPontide domain was characterized by an oceanic basin opened at least in the Early Jurassic. The opening of the IntraPontide oceanic basin was followed by the development of a subduction zone with a consequent opening of suprasubduction oceanic basin in the Middle Jurassic – Early Cretaceous time span. The convergence in this suprasubduction oceanic basin started at the Early/Late Cretaceous boundary by an obduction process, whereas its final closure can be regarded as Late Paleocene in age
Metamorphic imprint of ridge subduction on the Neo-Tethyan ophiolites from the Saka Unit (Central Pontides, northern Turkey)
No full textThe Intra-Pontide suture zone is the northernmost ophiolite suture zone exposed in the Anatolian peninsula. It consists of several variably deformed and metamorphosed tectonic units derived from the Neo-Tethyan Intra-Pontide oceanic (IPO) basin, and its continental margins that are currently represented by the Istanbul-Zonguldak and the Sakarya terranes. Recent data suggests that the IPO was a wide supra-subduction oceanic basin whose closure began in the uppermost Early Jurassic by a north dipping intra-oceanic subduction that divided the IPO into two different oceanic areas, namely IPO1 and IPO2. The Saka Unit is a small tectonic unit exposed in the eastern portion of the Intra-Pontide suture zone in the Central Pontides, which is interpreted as a tectonic mélange produced during the intra-oceanic subduction that led to the closure of IPO1. The unit was affected by polyphase deformation and epidote–amphibolite facies metamorphism peak conditions experienced during the uppermost Middle Jurassic. Metamorphic studies and thermodynamic investigations constrain the peak pressure conditions to T ≈ 650–700 °C and P ≈ 0.9–1.3 GPa. These conditions reveal a ‘hot’ and anomalous geothermal gradient (15–22 °C/km) with respect to those of the other ophiolite-bearing units of the Intra-Pontide suture zone involved in the subduction. This anomalous gradient was herein attributed to the thermal pulse produced by the subduction of the IPO1 mid-oceanic ridge. The final re-equilibration occurred under greenschist facies conditions during the Early Cretaceous exhumation, when the oceanic lithosphere of the IPO was completely consumed and the continental collision between the Istanbul-Zonguldak and Sakarya terranes occurred
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