Zeynep Ozbey

Bio: Zeynep Ozbey is an academic researcher from Istanbul University. The author has contributed to research in topics: Continental margin & Gondwana. The author has an hindex of 3, co-authored 4 publications receiving 35 citations.

Tectonic significance of Late Ordovician granitic magmatism and clastic sedimentation on the northern margin of Gondwana (Tavşanlı Zone, NW Turkey)

Abstract: Metasedimentary schists and a small crosscutting metagranite underlie a Mesozoic metamorphosed carbonate platform within the regional Anatolide tectonic belt of northern Turkey. These lithologies are inferred to have formed part of the northern margin of Gondwana during the Palaeozoic. Immobile element geochemistry suggests that the country rock metasediments were derived from upper continental crust and arc-type magmatic rocks. Major and trace element analyses of the metagranite indicate affinities with upper continental crust or a continental margin magmatic arc. Tectonic discrimination of the metagranite is consistent with a rift or post-collisional setting. Niobium depletion relative to Ce on primitive mantle-normalized spidergrams suggests a subduction influence, possibly inherited from Late Precambrian (Cadomian) arc magmatism. Ion microprobe U–Pb dating of zircons from the metagranite yielded a crystallization age of 446 ± 8 Ma (Late Ordovician). An inherited core gave a concordant age of c . 578 Ma, consistent with Cadomian or Pan-African basement. Regional comparisons indicate that the Palaeozoic lithostratigraphy is similar to that of the Taurides (Gondwana) rather than the Pontides (Laurasia). We infer Mid- to Late Ordovician crustal extension along the north Gondwana margin, followed by spreading of Palaeotethys. The entire stratigraphy experienced high-pressure/low-temperature metamorphism during Late Cretaceous closure of the Izmir–Ankara–Erzincan ocean. Supplementary materials: The mineral composition, fabric, coordinates (UTM) and modal composition of the Beyce schist and Sarikaya metagranite samples are available at www.geolsoc.org.uk/SUP18556.

Mesozoic magmatic and sedimentary development of the Tavşanlı Zone (NW Turkey): implications for rifting, passive margin development and ocean crust emplacement

Abstract: Abstract Upper Ordovician–Upper Cretaceous high-pressure–low-temperature metasedimentary and meta-igneous rocks in the Dursunbey area provide insights into the Tavşanlı Zone (Anatolides) when compared to crustal units further south (e.g. Afyon Zone and Taurides). Schists near the base of the Tavşanlı Zone succession are cut by a small Upper Ordovician metagranite. This is covered by metaclastic sediments that are interbedded with bimodal rift-related basic-silicic volcanics of inferred Triassic age. Above this is a thick metacarbonate platform interpreted as the result of post-rift subsidence. Overlying metacarbonates, metapelites and metachert with metabasaltic intercalations (Upper Cretaceous?) reflect platform collapse. Overlying mélange contains blocks of ocean-derived intrusive and extrusive igneous rocks (e.g. ocean island-type basalt), metacarbonates and radiolarian chert, set in a low-grade metamorphosed shaly matrix. The Tavşanlı Zone was buried in a north-dipping subduction zone to 74–79 km at c. 88 Ma, exhumed and tectonically juxtaposed with accretionary mélange prior to the Late Palaeocene–Early Eocene. Geochemical studies of the meta-igneous rocks indicate the presence of ocean island basalt (OIB) and mid-ocean ridge basalt (MORB) sources modified by crustal contamination, evidenced by Th enrichment and fractional crystallization. A subduction chemical influence in the lower part of the succession (e.g. Nb depletion) was probably derived from subcontinental mantle lithosphere, modified during some previous subduction event (Panafrican?). supplementary-material: Full geochemical data are available at www.geolsoc.org.uk/SUP18570

First evidence for the subduction initiation and boninitic magmatism from the Armutlu Peninsula (NW Turkey): geodynamic significance for the Cadomian magmatic arc system of the Gondwanan margin

Abstract: The Cadomian Orogeny was active along the northern margin of Gondwanaland during the Late Neoproterozoic–Early Cambrian period. Remains of this orogenic activity are traced from Western Europe to t...

Overview of the Palaeozoic–Neogene evolution of Neotethys in the Eastern Mediterranean region (southern Turkey, Cyprus, Syria)

Abstract: Valid palaeotectonic and palaeogeographical reconstructions of the easternmost Mediterranean and adjacent region involve a long-lived Tethys (Rheic, Palaeotethyan and Neotethyan oceans), northward subduction beneath Eurasia and rifting of continental fragments from Gondwana. Rifted microcontinents bordering Gondwana were separated (from south to north) by the Southern Neotethyan ocean, the Berit ocean (new name), the Inner Tauride ocean and the Izmir–Arkara–Erzincan ocean. Mid-Permian to Mid-Triassic pulsed rifting culminated in Late Triassic–Early Jurassic spreading of the Southern Neotethyan oceans (the main focus here). After Early–Mid-Jurassic passive subsidence, the Late Jurassic–Early Cretaceous was characterized by localized alkaline, within-plate magmatism related to plume activity or renewed rifting. Late Cretaceous ophiolites formed above subduction zones in several oceanic basins. Ophiolites were emplaced southwards onto the Tauride and Arabian platforms during the latest Cretaceous. The Southern Neotethys sutured with the Arabian margin during the Early–Middle Miocene, while oceanic crust remained in the Eastern Mediterranean further west. The leading edge of the North African continental margin, the Eratosthenes Seamount, collided with a subduction trench south of Cyprus during the Late Pliocene–Pleistocene, triggering rapid uplift. Coeval Plio-Quaternary uplift of the Taurides may relate to break-off or delamination of a remnant oceanic slab.

Early Paleozoic tectonics of Asia: Towards a full-plate model

Abstract: Asia is key to a richer understanding of many important lithospheric processes such as crustal growth, continental evolution and orogenesis. But to properly decipher the secrets Asia holds, a first-order tectonic context is needed. This presents a challenge, however, because a great variety of alternative and often contradictory tectonic models of Asia have flourished. This plethora of models has in part arisen from efforts to explain limited observations (in space, time or discipline) without regard for the broader assemblage of established constraints. The way forward, then, is to endeavor to construct paleogeographic models that fully incorporate the diverse constraints available, namely from quantitative paleomagnetic data, the plentiful record of geologic and paleobiologic observations, and the principles of plate tectonics. This paper presents a preliminary attempt at such a synthesis concerning the early Paleozoic tectonic history of Asia. A review of salient geologic observations and paleomagnetic data from the various continental blocks and terranes of Asia is followed by the presentation of a new, full-plate tectonic model of the region from middle Cambrian to end-Silurian time (500–420 Ma). Although this work may serve as a reference point, the model itself can only be considered provisional and ideally it will evolve with time. Accordingly, all the model details are released so that they may be used to test and improve the framework as new discoveries unfold.

Constraints on Variscan and Cimmerian magmatism and metamorphism in the Pontides (Yusufeli–Artvin area), NE Turkey from U–Pb dating and granite geochemistry

Abstract: Metamorphic and igneous rocks exposed in NW-vergent thrust sheets and their autocthonous basement in the NE Pontides were dated by the U–Pb method using zircons, supported by geochemical data for granitic rocks. Two meta-sedimentary units (Narlik schist and Karadag paragneiss) yielded detrital zircon populations of 0.50–0.65 and 0.9–1.1 Ga, suggesting an affinity with NE Africa (part of Gondwana). The youngest concordant zircon age is Ediacaran for the schist but Devonian for the paragneiss, bracketing the paragneiss depositional age as Mid-Devonian to Early Carboniferous. Metamorphic rims of zircon cores in the paragneiss gave Carboniferous ages (345–310 Ma). The zircon rim data indicate two Variscan metamorphic events (334 and 314 Ma) separated by a hiatus (320–325 Ma). Granite emplacement took place during early Carboniferous, Early Jurassic and Late Jurassic phases. The crystallization age of the early Carboniferous granites (c. 325 Ma) corresponds to a hiatus in the zircon age data that could reflect subduction slab break-off. The Variscan granitic rocks intruded a Gondwana-derived continental terrane that was loosely accreted to Eurasia during early–late Carboniferous time but remained isolated from Eurasian-derived terrigenous sediment. In contrast, the Jurassic granitic magmatism relates to later back-arc extension along the southern margin of Eurasia. Supplementary material: Full isotope data (8 tables) are available at www.geolsoc.org.uk/