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Öğe Active tectonics of the Ortakoy fissure-ridge-type travertines: implications for the Quaternary stress state of the neotectonic structures of the Central Anatolia, Turkey(TAYLOR & FRANCIS LTD, 2012) Mesci, B. LeventSeveral geothermal fields are located in a NE-SW trend along a structural lineament around the Sivas basin; one of those is the Ortakoy travertines situated 83km south-west of Sivas. There are eight fissure-ridge-type travertine localities in the area, although eroded-sheet-type travertines constitute many of the travertines of the region. By evaluating the rocks of the Late Miocene-Early Pliocene Kzlrmak Formation, it was determined that fissure axes developed within fissure-ridge-type travertines, and that the structural elements obtained from satellite images together with the fissures that form the fissure-ridge-type travertines are shear and tension fissures, and the NE-SW-oriented opening of the fissures, were a result of NW-SE-directed compression, which was also responsible for the formation of the Sivas Backthrust. Ground-penetrating radar studies have shown that the thickness of fissure fills within the fissure-ridge-type travertines of the Ortakoy geothermal field increase with depth, and that the hydrothermal fluids which brought about the formation of the travertines moved surfaceward via fissure systems. The results of U/Th radiometric dating indicate that the youngest travertine in the region is 17,761 ((-268)/(+269)) years old and the oldest 128,286 ((-3537)/(+3662)) years old. Using the widths of banded travertines within the fissure-ridge-type travertines as well as these age results, the opening rate of the Sivas Basin was determined to be .06 ((-.01)/(+.05)) mm/year.Öğe Anadolu Bloğu - Arap levhasının neotektonik dönem çarpışma sürecinde gelişen kabuksal deformasyonun paleomanyetik yöntemlerle analizi(2007) Gürsoy, Halil; Tatar, Orhan; Pıper, John D.A.; Koçbulut, Fikret; Mesci, B. Levent[Abstract Not Available]Öğe Crustal deformation and kinematics of the Eastern Part of the North Anatolian Fault Zone (Turkey) from GPS measurements(ELSEVIER SCIENCE BV, 2012) Tatar, Orhan; Poyraz, Fatih; Gursoy, Halil; Cakir, Ziyadin; Ergintav, Semih; Akpinar, Zafer; Kocbulut, Fikret; Sezen, Fikret; Turk, Tarik; Hastaoglu, Kemal O.; Polat, Ali; Mesci, B. Levent; Gursoy, Onder; Ayazli, I. Ercument; Cakmak, Rahsan; Belgen, Alpay; Yavasoglu, HakanThe North Anatolian Fault Zone (NAFZ) is a 1200 km long dextral strike-slip fault zone forming the boundary between the Eurasian and Anatolian plates. It extends from the Gulf of Saros (North Aegean) in the west to the town of Karliova in eastern Turkey. Although there have been numerous geodetic studies concerning the crustal deformation, velocity field and the slip rate of the NAFZ along its western and central segments, geodetic observations along the eastern section of the NAFZ are sparse. In order to investigate the GPS velocities and the slip rate along the eastern part of the NAFZ, a dense GPS network consisting of 36 benchmarks was installed between Tokat and Erzincan on both sides of the fault zone and measured from 2006 to 2008. Measurement results indicate that the slip rate of the NAFZ increases westwards within about 400 km from 16.3 +/- 2.3 mm/year to 24.0 +/- 2.9 mm/year, in consistence with the observation that the Anatolian block is being pulled by the Hellenic trench rather than being pushed by the Arabian plate as a result of continental collision between the Arabian and Eurasian plates in eastern Turkey since late Miocene. Modelling the GPS velocities shows that fault locking depth increases also in the same direction from 8.1 +/- 3.3 km to 12.8 +/- 3.9 km. Slip rate decreases as moving off the Hellenic trench. An average slip rate of 20.1 +/- 2.4 mm/year and a locking depth of 12.5 +/- 3.5 km are also estimated for the entire study area by using all of the GPS measurements obtained in this study. The GPS velocities are in good agreement with the kinematic models created by paleomagnetic studies in the region and complete the overall picture. (C) 2011 Elsevier B.V. All rights reserved.Öğe Determination of neotectonic features of the Karasu Basin (SE Turkey) and their relationship with Quaternary volcanic activity using Landsat ETM plus imagery(TAYLOR & FRANCIS LTD, 2009) Kavak, Kaan Sevki; Tatar, Orhan; Piper, John; Kocbulut, Fikret; Mesci, B. LeventThe junction between the East Anatolian and the Dead Sea fault zones lies close to an unstable F: Transform fault (FFF) triple junction where the African, Eurasian and Arabian plates meet in south-eastern Turkey. The Karasu Basin is an ephemeral rifted structure located close to the junction of these plate boundaries and is expressed by a range of tectono-morphological features. This study uses remote sensing to define tectonic structures and discriminate volcanic rocks linked to rifting within the basin using Landsat Enhanced Thematic Mapper Plus (ETM+) imagery. Prior to advanced image processing stages, images were corrected to eliminate atmospheric scattering effects and determine the best band combination for multi-spectral processing techniques based on statistical methods. Following preprocessing stages, edge detection filters were applied to derive tectonic structures defining the basin. The Brovey transformation, a statistical data merging method, was used to combine reflective multi-spectral bands with the Landsat ETM+ panchromatic band. This method fuses higher spatial data with data of lower spatial value. The western margin of the Karasu Basin is defined by the left-lateral Amanos Fault Zone with a contemporary motion (c. -0.4 mm a(-1)) probably accommodating most of the left-lateral strike-slip motion between Arabian and African plates on the northern continuation of the Dead Sea Fault Zone. The rift zone has been the site of extensive recent volcanism concentrated within the Brunhes Chron (< 0.78 Ma) and linked to fault block rotations between the intracontinental master faults. The boundaries of this activity are defined here using a regolith mapping technique.Öğe The evolution of travertine masses in the Sivas area (Central Turkey) and their relationships to active tectonics(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2008) Mesci, B. Levent; Gursoy, Halil; Tatar, OrhanSicak Cermik, Delikkaya and Sarikaya are important travertine fields with active hot springs located 31 km west of Sivas. Based on their morphology, most of the travertines are classified as fissure-ridge travertines. Eroded sheet-type, terraced, and self-built channel types of travertine are also present at a few locations. Faults and fissures formed in the underlying incesu Formation, and fissures developing in the fissure-ridge travertines are linked to one another. Tectonic deformation forming the fissure-ridge travertines resulted from NE-SW extension associated with a NW-SE compressional regime related to the Central Anatolian Thrust Belt and Sivas Backthrust. U/Th series age dating results indicate that the travertine deposition extends back to 400 ka and yields ages of 11.400 (+/- 500) to 364.000 ((+201.000)/(-76.000)) from the fissure-ridge travertines. Age data and fissure width observations indicate that a similar to 0.06 mm/year extension rate is associated with the compressional regime in the Sivas Basin. On average, fissure-ridge travertines formed over intervals of 56.000 years, and indicate that a major regional seismic event with a magnitude of 7.4 has occurred here with this order of frequency. The Pamukkale travertines in Western Turkey are one of the most spectacular natural heritage sites in the world, as well as a site of active tectonic studies, and are now protected for these reasons. As shown by this study, the Sicak Cermik travertines are of comparable interest and should receive similar protection.Öğe Fossil findings from the Sicak Cermik fissure ridge-type travertines and possible hominid tracks, Sivas, Central Turkey(TAYLOR & FRANCIS LTD, 2017) Mesci, B. Levent; Erkman, Ahmet Cem; Gursoy, Halil; Tatar, OrhanSicak Cermik (Sivas) is an important geothermal and recent travertine formation area in Central Anatolia. The majority of travertines found in the region comprise fissure-ridge type travertines according to morphological classification. At the location called Tepe Cermik within the travertine area, fill containing fossil bone fragments of Equus sp., Bovidae and other abundant animals formed within the fracture axis of a N-S striking fissure-ridge travertine developed under control of tectonic forces. The finds of these fossils in fissure-ridge travertines linked to tectonic forces indicates formation of a unique fossil environment created under the control of these forces. The Accelerator Mass Spectrometry Radiocarbon Dating analyses of fossils from the study area determined the fills were older than 43,000 years. The U/Th age of a sample from the most recently-formed banded travertine in the axis of the fracture was identified as 278,540 +/- 18,436 years. As a result, the ages of fossils found within this fill are thought to be between 43,000 and 278,540 +/- 18,436 years old. The high amount of perissodactyla and artiodactyla fossils found within fill in the axis of the fissure-ridge travertine probably indicates the presence of hominids who chose the region for hunting or settlement. The Equus sp. and Bovidae fossil samples found in the axis of the fracture indicate that in the dry and cold glacial period the paleogeography in a large portion of Anatolia comprised desert-like steppe.Öğe Intracontinental quaternary volcanism in the Niksar pull-apart basin, North Anatolian Fault Zone, Turkey(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2007) Tatar, Orhan; Yurtmen, Sema; Temiz, Haluk; Guersoy, Halil; Kocbulut, Fikret; Mesci, B. Levent; Guezou, Jean ClaudeThe Niksar Basin is sited along the eastern segment of the North Anatolian Fault Zone in Turkey. It is a young sigmoidal pull- apart basin bordered by two non- parallel master faults associated with earthquakes in 1939 and 1942. The fault geometry along the irregular ENE margin of the basin is complex where young Plio - Quaternary volcanic rocks reach the surface along pairs of steep strike- slip faults which cut the basin sediments. The volcanic rocks around the Niksar Basin have been dated by high precision K- Ar dating and the ages range between 542 +/- 9 ka and 567 +/- 9 ka. The lavas are mainly alkaline ( sodium dominated) in nature and include basaltic trachandesite ( mugearite) and trachyandesite ( benmoreite) with minor sub- alkaline compositions of dacitic andesite, rhyodacite and rhyolite. Despite the large compositional gap between basaltic and felsic lavas, major and trace element distributions indicate that both the basaltic and felsic lavas are cogenetic. Abundances of major oxides and trace elements vary systematically through this compositional spectrum. Fractional crystallization of the observed phases accounts for the diversity of intermediate and evolved products. Amphibole fractionation in basalts at depth causes the trend towards silica saturation while alkali feldspar fractionation dominates the final stages of crystallization. Significant crustal contamination has occured in the evolved magmas but contamination is generally minimal or absent in their basaltic parents. Alkaline basaltic rocks have OIB ( ocean island basalt) like trace element patterns characterized by enrichment in LILE, HFSE, LREE and slight depletion in HREE relative to primitive mantle values. Overall geochemical variations indicate the combined effects of different degrees of partial melting, fractional crystallization and variable degrees of crustal contamination.Öğe Ölü Deniz ve Doğu Anadolu Fay zonlarının kesişim bölgesindeki kabuksal deformasyonunun paleomanyetik ve jeokronolojik(2004) Tatar, Orhan; Kavak, K. Şevki; Mesci, B. Levent; Heımann, Ariel; Pıper, D.A.; Yurtmen, Sema; Gürsoy, HalilTürkiye'nin güneyinde Neotetis okyanusunun kuzeye doğru yitimi sonucu oluşan Arabistan ve Anadolu plakalarının çarpışması, Alp-Himalaya kuşağındaki en karmaşık kabuk içi deformasyonun izlendiği bölgelerden birisinin oluşumunu sağlamıştır. Önemli atımlara sahip, Ölü Deniz Fay Zonunun kuzey uzantısını da içeren birçok ana transform fay bu bölgede kesişmektedir. ÖDFZ'nun kuzey uzantısı olduğu varsayılan Amanos ve Doğu Hatay Fayları ile bu bölgenin doğusunda kalan Ceyhan-Osmaniye yöresindeki volkanizmanın paleomanyetik özelliklerinin saptanması, bölgenin neotektonik gelişiminin ve kabuksal deformasyonun daha iyi anlaşılmasını sağlayacaktır. Ceyhan-Osmaniye yöresinde yüzeyleyen volkanizma sol yanal Karataş-Osmaniye Fay Zonu ile Neotetis okyanusuna ait kenet kuşağına yakın bir bölgede yoğunlaşmıştır. Osmaniye yöresinde 9 ayn istasyondan alınan örnekler normal polarite sunmakta, çok genç morfolojik görünümleri bunların Bruhnes manyetik polarite evresinde (<780 ka) oluştuğunu göstermektedir. Bu volkanik kayaçlardaki deklinasyon değerleri çoğunlukla saatin yönündedir. Bu yaş verisi, İskenderun körfezinin kuzey ucunda Ceyhan nehir yatağının değişimine de neden olan çok hızlı bir yükselmenin varlığını işaret etmektedir. 8 istasyona ait grup ortalama paleomanyetizma yönleri 11.3±10° saatin yönünde rotasyon göstermektedir. Bu volkanik arazinin GB uzantısında Botaş rafinerisinin bulunduğu alanda da 7 ayrı istasyonda örnekleme yapılmış ve bu örneklerin ters manyetik polariteye sahip olduğu anlaşılmış ve 43.7±7° saatin tersi yönde rotasyona uğradıkları saptanmıştır. Karasu havzasında yapılan paleomanyetik çalışmalarda kalıntı manyetizmanın düşük Ti manyetitler içerdiği ve 51 örnekleme istasyonundan 5'i hariç diğerlerinin normal polarite gösterdiği belirlenmiştir. Bölgede elde edilen morfolojik, K-Ar yaş ve manyetik polarite değerleri havza oluşumunun çoğunlukla Bruhnes manyetik polarite evresinde oluştuğunu gösterir. Bu evredeki volkanizma 0.66-0.35 My ve -0.25-0.05 My arasında yoğunlaşmıştır. 44 örnekleme istasyonu , Günümüz manyetik alanına uygun şekilde D/l = 8.8°/54.7° normal polarite değeri göstermekte ve bu değerler 8.8°±4.0° saatin yönünde rotasyonu ifade etmektedir. Karasu havzasının -15 km genişliğindeki Hassa bölümünde volkanik aktivite sol yanal hareket gösteren Amanos ve Doğu Hatay fayları arasında gelişmiştir. Her iki fay da Arabistan plakasının kuzeye hareketine bağlı olarak saatin yönünde hareket gösteren KB-GD uzanımlı çapraz (cross) faylarla sınırlı, rotasyona uğramış bloklar içermektedir. - 0.5 My'lık ortalama lav akıntısı yaşı, sistemi sınırlayan faylar üzerinde 0.46 cm/yıl hareket hızı vermektedir. Amanos Fayı üzerindeki morfolojik yapılar, yaşlandırılmış lav akıntılarının ötelenmesinden elde edilmiş hareket hızı tahminleri bu değerden daha azdır. Bu, olasılıkla eldeki verilerin sismojenik kabuğa kadar ulaşmayan yüzey kırıklarından elde edilmiş olmasından kaynaklanmaktadır. Bu çalışmanın sonuçları, ÖDFZ üzerindeki atımın büyük bir bölümünün, Amanos, Doğu Hatay ve Afrin fayları tarafından karşılandığını göstermektedir. Kuvaterner'deki karşılaştırabilir atım oranı tahminleri FFF birleşme noktasındaki (ÖDFZ, DAFZ, KOFZ) diğer faylar üzerinde de belirlenmiştir. ÖDFZ ve kuzeye uzantısı faylar üzerindeki Pliyo-Kuvaterner dönemindeki atım oranındaki değişim son 1-3 My'daki tektonik rejim değişikliği, Anadolu'nun tektonik kaçışı ile KAFZ ve DAFZ'larımn oluşumu ile karşılaştırabilir. Bu bölgede son 1 My'daki bazaltik magmanın oluşumu ve tektonik rejimin transpresyonelden transtansiyonel rejime dönüşümü de bu olaylarla ilişkilidir.Öğe Palaeomagnetic evidence for the neotectonic evolution of the Erzincan Basin, North Anatolian Fault Zone, Turkey(PERGAMON-ELSEVIER SCIENCE LTD, 2013) Tatar, Orhan; Akpinar, Zafer; Gursoy, Halil; Piper, John D. A.; Kocbulut, Fikret; Mesci, B. Levent; Polat, Ali; Roberts, Andrew P.Ongoing motion of Anatolia towards the west is caused by convergence of the Arabian and Eurasian plates coupled with suction towards the retreating Hellenic Arc. This regime is controlling the development of neotectonic structures in Turkey with the resulting distributed deformation accommodated primarily between the East and North Anatolian Intracontinental Transform Faults. The Erzincan Basin is developed along the eastern part of the latter fault and although it incorporates one of the largest Quaternary basins in Turkey, the duration and tectonic evolution are disputed. Tectonic models proposed to explain the basin range from simple rhomboidal pull-apart to a complex multi-phase evolution. To help constrain the age and tectonic regime(s) forming the basin we have conducted a palaeomagnetic and geochronologic study of volcanic domes which occur mainly in proximity to strike-slip faulting along the northern margin of the basin. The investigated sample comprises 27 lava sites located within 14 cones, 13 to the north and one in the south. Although difficult propositions for palaeomagnetic investigation because the young predominantly-pyroclastic constructive topography is susceptible to collapse, all sites show positive inclinations and mainly northerly declinations showing that they are the consequence of a tectonic regime confined to the Brunhes Chron. Whilst the limitation of directional data from these young constructive features is stressed, ten cones are found to show clockwise rotations ranging from 12 degrees to 195 degrees with three cones showing no significant rotation. Geochronological studies from 13 samples yield a range of ages with 6 providing meaningful results <0.3 Myr in age and consistent with young ages evident from morphology and paleomagnetism. AMS (Anisotropy of Magnetic Susceptibility) studies identify a fabric related to downslope flow at most sites with the majority moving away from conduits controlled by fractures paralleling the dominant NW-SE trend of the master fault. The palaeomagnetic and geochronologic results show that the history of the Erzincan Basin has involved at least two phases with the later phase incoporating an extensional component permitting access to mantle melts and confined to the last similar to 300,000 years. The earlier phase commenced in Late Miocene or Early Pliocene times and initiated the rift infill which currently attains a maximum thickness in excess of 2.7 km. We propose that the Erzincan Basin is now segmented as a mature basin by strike-slip cross faults although these cannot explain the consistent clockwise rotations observed within the small blocks incorporating the volcanic cones because these are confined to a narrow zone between two master faults and appear to be subject to ball-bearing style rotation. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Travertines with original features and their importances: Examples from the Sivas travertines(Tmmob Jeoloji Muhendisleri Odasi, 2013) Mesci, B. LeventTravertine is sedimentag rock which formed under chemical and/or biochemical processes from geothermal waters and consists very long time periods and very special geological processes. Well-known travertine areas are now under protection hut majority of travertine areas is remote from any control and operating and used as quarry Travertine and travertine areas has an great important in terms of their active tectonics data, geological characteristics, earth science education and scientific researches. The importance of travertine outcrops is not limited with earth science. Travertines have also archaeological, anthropological and touristical values. Importance of the travertines should be carefully evaluated before they are operated as an quarries in order to determine the presence or absence of its original features. According to the results of this evaluation the original features travertine areas should be protected and avoided from damages.
