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Öğe An Extensional Fracture Acting as Hot Water Source for Travertine Deposition on the North Anatolian Fault Zone, Turkey: the Resadiye Fissure-Ridge(Tmmob Jeoloji Muhendisleri Odasi, 2020) Mesci, Bekir Levent; Gursoy, Halil; Ghaleb, Bassam; Tatar, OrhanThe Resadiye (Tokat) geothermal field is located in the northern part of the right-lateral North Anatolian Fault Zone. Geothermal waters at temperatures between 48-52 degrees C from this geothermal field are currently used mostly in hotels, pools and bathrooms and provide significant tourism potential for the region. The area where the geothermal sites are located includes a similar to NW-SE trending fissure-ridge type travertine with a length of about 600 meters. Approximately 500 meters south of the geothermal field and parallel to the Kelkit River, the active segment of the North Anatolian Fault Zone comprises the Kelkit Valley fault segment extending N72 degrees W. The average strike direction of Resadiye fissure-ridge type travertine is around N33 degrees W. There is an angle of 39 degrees between the master trend of NAFZ and the direction of the Resadiye fissure-ridge travertine. This 39 degrees angle between the extensional cracks in the fissure-ridge travertine and the NAFZ is compatible with extensional fractures developing in well-formed strike-slip faults at an angle of similar to 45 degrees with the master fault. U/Th determination of two samples from banded travertines from the travertine deposits yielded ages of 7,563 and 12,529 years. Combined with other evidence, the samples indicate an opening rate of 0.093 mm/year for the Resadiye geothermal travertine field.Öğe Ar-40/Ar-39 dating of ignimbrites and plinian air-fall layers from Cappadocia, Central Turkey: Implications to chronostratigraphic and Eastern Mediterranean palaeoenvironmental record(ELSEVIER GMBH, 2014) Lepetit, Petra; Viereck, Lothar; Piper, John D. A.; Sudo, Masafumi; Gurel, Ali; Copuroglu, Ibrahim; Gruber, Manuela; Mayer, Bernhard; Koch, Michael; Tatar, Orhan; Gursoy, HalilMagmatism forming the Central Anatolian Volcanic Province of Cappadocia, central Turkey, records the last phase of Neotethyan subduction after similar to 11 Ma. Thirteen large calc-alkaline ignimbrite sheets form marker bands within the volcano-sedimentary succession (the Urgup Formation) and provide a robust chronostratigraphy for paleoecologic evaluation of the interleaved paleosols. This paper evaluates the chronologic record in the context of the radiometric, magnetostratigraphic and lithostratigraphic controls. Previous inconsistencies relating primarily to K/Ar evidence were reason for the initiation of an integrated study which includes Ar-40/Ar-39 dating, palaeomagnetic and stratigraphic evidence. The newly determined Ar-40/Ar-39-ages (Lepetit, 2010) are in agreement with Ar/Ar and U/Pb data meanwhile published by Pauquette and Le Pennec (2012) and Aydar et al. (2012). The Ar-40/Ar-39-ages restrict the end of the Urgup Formation to the late Miocene. The paleosol sequence enclosed by the ignimbrites is thus restricted to the late Miocene, the most intense formation of pedogene calcretes correlating with the Messinian Salinity Crisis. (C) 2014 Elsevier GmbH. All rights reserved.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 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 Geophysical analysis of fault geometry and volcanic activity in the Erzincan Basin, Central Turkey: Complex evolution of a mature pull-apart basin(PERGAMON-ELSEVIER SCIENCE LTD, 2016) Akpinar, Zafer; Gursoy, Halil; Tatar, Orhan; Buyuksarac, Aydin; Kocbulut, Fikret; Piper, John D. A.The Erzincan Basin is one of several Neogene sedimentary basins developed by prolonged right-lateral strike-slip along the North Anatolian Fault Zone (NAFZ), the intracontinental transform defining the present boundary between the Eurasian Plate to the north and accreted Anatolian terranes to the south. The basin has a strong asymmetry and young (<780 ka) volcanic centers with widespread development of cross faults defining an advanced phase of pull-apart basin evolution. To isolate faults with no surface geomorphic or morphotectonic signatures in the young sedimentary cover, continuous magnetic profiles were conducted together with detailed interpretation of the regional Bouguer gravity map. This geophysical approach combined with surface mapping defines a fault geometry highlighting a series of buried structures including a fracture system 0.2-2.35 km wide which conforms to the volcanic lineaments seen at the surface. A model is developed for the evolution of the Erzincan Basin with a history commencing as a simple pull-apart by right-lateral strike-slip on the developing NAFZ, probably in Early Pliocene times. Subsequent interaction with a major left-lateral (Ovacik) fault (OF) caused the focus of motion on the NAFZ to shift to the southwest and develop a complex fishbone fracture system. This became the focus of volcanic activity on three lineaments which migrated progressively southwards toward the axis of the basin. Continuing motion on the OF transformed the south east margin of the basin into an extensional zone and the tectonic history of the basin has been further complicated by its proximity to a major transform intersection between the NAFZ and OF. The signatures of recent volcanism and the development of cross faults on which much activity is now concentrated define a mature pull-apart advancing toward extinction. (C) 2015 Elsevier Ltd. All rights reserved.Öğe New observations on the 1939 Erzincan Earthquake surface rupture on the Kelkit Valley segment of the North Anatolian Fault Zone, Turkey(PERGAMON-ELSEVIER SCIENCE LTD, 2013) Gursoy, Halil; Tatar, Orhan; Akpinar, Zafer; Polat, Ali; Mesci, Levent; Tuncer, DoganThe 1939 Erzincan Earthquake (M=7.8), occurred on the North Anatolian Fault Zone (NAFZ), was one of the most active strike-slip faults in the world, and created a 360-km-long surface rupture. Traces of this surface rupture are still prominently observed. In the absence of detailed mapping to resolve the fault characteristics, detailed observations have been conducted at 20 different points on the 70-km-long Kelkit Valley Segment (INS) of the NAFZ's between Niksar and Koyulhisar. Field data defining fault character and slip amounts were found at eight points and show right-lateral slip varying between 1.8 and 4.25 m and the vertical slip varying between 0.5 and 2.0 m. The KVS developed in the most morphologically prominent and narrowest part of the NAFZ. Therefore, the chances of finding evidence of more than one historical earthquake in trenches opened to investigate palaeoseismological aspects are higher. Faults observed in foundation and channel excavations opened for energy purposes in the Resadiye region show this clearly and evidence for up to four seismic events including the 1939 Erzincan Earthquake have been discovered. Further studies are required to discover whether right-lateral deformation on at some locations on this segment is surface ruptures associated with the 1939 earthquake or later creep. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.Öğe Palaeoearthquakes on the Kelkit Valley Segment of the North Anatolian Fault, Turkey: Implications for the Surface Rupture of the Historical 17 August 1668 Anatolian Earthquake(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2011) Zabci, Cengiz; Akyuz, Husnu Serdar; Karabacak, Volkan; Sancar, Taylan; Altunel, Erhan; Gursoy, Halil; Tatar, OrhanThe 26 December 1939 Erzincan (M-s = 7.8) and 20 December 1942 Erbaa-Niksar (M-s = 7.1) earthquakes created a total surface rupture more than 400 km between Erzincan and Erbaa on the middle to eastern sections of the North Anatolian Fault. These two faulting events are separated by a 10-km-wide releasing stepover, which acted like a seismic barrier in the 20(th) century. To understand the rupture behaviour in this structurally complex section of the North Anatolian Fault, we undertook palaeoseismological trench investigations on the Kelkit Valley segment where there is little or no palaeoseismic information. We found evidence for three surface faulting earthquakes predating the 1939 event during the past millennium in trenches excavated in Resadiye and Umurca. In addition to the 1939 Erzincan earthquake, prior surface ruptures are attributed to the 17 August 1668, A.D. 1254 and A.D. 1045 events. Surface rupture of the 17 August 1668 Anatolian earthquake was previously reported in palaeoseismological studies, performed on the 1944, 1943, and 1942 earthquake fault segments. We suggest that the surface rupture of this catastrophic event jumped the 10-km-wide releasing stepover in Niksar and continued eastward to near Koyulhisar. The existence of different amount of off sets in field boundaries (sets of 4 m, 6.5 m, and 10.8 m) was interpreted as the result of multiple events, in which the 1939, 1668, and 1254 surface ruptures have about 4, 2.5, and 4 metres of horizontal coseismic slip on the Kelkit Valley segment of the North Anatolian Fault, respectively.Öğe Palaeomagnetic and rock magnetic properties of travertine: Its potential as a recorder of geomagnetic palaeosecular variation, environmental change and earthquake activity in the Sicak Cermik geothermal field, Turkey(ELSEVIER SCIENCE BV, 2007) Piper, John D. A.; Mesci, Levent B.; Gursoy, Halil; Tatar, Orhan; Davies, Ceri J.Travertine, the product of incremental growth of inorganic carbonate, is potentially a high-resolution recorder of geomagnetic palaeosecular variation (PSV) when it incorporates small amounts of ferromagnetic material. It grows most regularly in regions of neotectonic activity where geothermal waters feed into extensional fissures and deposit successive layers of carbonate as fissure travertine. The same waters spill out onto the surface to deposit bedded travertine which may incorporate wind blown dust including ferromagnetic particles. Tectonic travertine deposits are linked to earthquake activity because the geothermal reservoirs are reset and activated by earthquake fracturing but tend to become sealed up by carbonate deposition between events. This study investigates whether sequential deposition can identify cycles of PSV and provide a means of estimating rates of travertine growth and earthquake frequency. The palaeomagnetic record in three travertine fissures from the Sicak Cermik geothermal field in Central Anatolia and nearby bedded travertines dated up to 360,000 years in age (U-Th) are investigated to evaluate magnetic properties and relate the geomagnetic signature to earthquake-induced layering. Sequential sampling of bedded travertine from the margins (earliest deposition) to centres of fissures (last deposition) identifies directional migrations reminiscent of PSV. Thermal demagnetisation shows that goethite pigment is not a significant remanence carrier; instead hematite, and more rarely magnetite, is the carrier. Magnetic susceptibility of fissure travertine is proportional to the calcite: aragonite ratio. Two-frequency susceptibility analysis identifies a ferromagnetic content in bedded travertine dominated by fine superparamagnetic grain sizes whereas the fissure travertine has mostly single and multidomain grain sizes, a difference interpreted to reflect contrasting energies of the two environments plus atmospheric input in the bedded travertine. Fissure travertine possesses strong lineated anisotropy of magnetic susceptibility (AMS), with horizontal k(max) axes oriented along the fissure axes and k(int) and k(min) distributed within the orthogonal plane; this is explained by rolling of ferromagnetic grains up the side of the fissure during repeated water ejection until fixed by the host carbonate precipitation. In contrast bedded travertine has low magnitude AMS with near neutral ellipsoid shapes controlled by settling of grains during weak outflow from the axis of the fissure ridge. The source of the magnetic minerals in the fissure travertine is probably in material washed down by meteoric waters from the local terra rossa soil and concentrations of these minerals (and hence magnetic susceptibility) could be a signature of pluvial environments. Fissure travertine is a reliable recorder of the ambient field when layered although bedded travertine is found to exhibit inclination shallowing. On the assumption that PSV cycles record periods of 1-2 ky, layering in the travertine identifies resetting of the geothermal system by earthquakes every 50-100 years in this region. Travertine precipitation occurs at rates of 0.1-0.3 mm/year on each side of the extensional fissures and possibly at a rate an order higher as bedded travertine on the surface. Earthquakes of magnitude M <= 4 occur much too frequently to have any apparent influence on travertine deposition but earthquakes with M = 4.5-5.5 occur with a frequency compatible with the travertine layering and appear to be the events recorded by the layering. Two signatures of much larger earthquakes on a 1-10 ky timescale are also recorded by travertine deposition. These are (i) incidental emplacement of massive travertine or fracturing of earlier travertine without destruction of the fissure as a venue of travertine emplacement and (ii) termination of the fissure as a site of deposition with transfer of geothermal activity to a new fracture. Palaeomagnetic estimates of fissure duration and the presence of some 25 fractures in the similar to 300,000 year old Sicak Cermik field growing at rates of 0.1-0.6 mm/year suggests that the type (ii) signature is achieved by an M similar to 7.5 event approximately every 10,000 years. (c) 2007 Elsevier B.V. All rights reserved.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 Paleoseismological Findings on the Ortakoy-Susehri Segment of the 1939 Erzincan Earthquake Surface Rupture, North Anatolian Fault Zone(Tmmob Jeoloji Muhendisleri Odasi, 2012) Polat, Ali; Tatar, Orhan; Gursoy, Halil; Karabacak, Volkan; Zabci, Cengiz; Sancar, TaylanThe study area is located within the Susehri-Golova basin on eastern part of the North Anatolian Fault Zone (NAFZ). Great devastating earthquakes have been occurred on this highly active seismic fault zone in near historical period. The last great earthquake causing loss of many life and properties was occurred on 27 December 1939 in Erzincan along the eastern part of the NAFZ. This earthquake has created hundreds of kilometers surface rupture, and can also be traced in the study area. Significant information is obtained by early paleoseismological studies carried out especially on the middle and western parts of the NAFZ proving important data about earthquake return periods and magnitudes of seismic activity in the period. Paleoseismological studies on eastern part of the NAFZ are less than western part of the NAFZ. In this study, three trenches were excavated on the 1939 Erzincan earthquake surface rupture. These trenches are located from west to east, in Eskibag, Asagiyenikoy and Asagitepecik villages. Eskibag trench was excavated on a sag pond to the southeast of Sevindik and northeast of Eskibag villages. Asagi Tepecik trench was excavated on the same lineament to the northeast of Asagiyenikoy where a clear fault morphology is observed. The Asagi Tepecik was excavated 2.5 km southeast of the Lake Sut. These trench data are significant because of showing data of large earthquakes repeated during Holocene times. Beside the fact that 1939 surface rupture was observed, the earthquake ruptures formed before 1939 were also observed on trench logs. It is showed that 1939 earthquake surface rupture follows older ruptures and reveals the existence of several different seismic activities prior to 1939 earthquake.Öğe Two-phased evolution of the Susehri Basin on the North Anatolian Fault Zone, Turkey(TAYLOR & FRANCIS LTD, 2012) Polat, Ali; Tatar, Orhan; Gursoy, Halil; Yalciner, C. Caglar; Buyuksarac, AydinThis study has aimed to evaluate the current tectonic structure of the Susehri Basin located on the eastern part of the North Anatolian Fault Zone (NAFZ), one of the most important active faults in Turkey. The work extends earlier investigations of offset and seismicity on the NAFZ and tests a range of evolutionary models. In this study, buried faults have been determined from Ground penetrating radar and magnetic anomalies and possible discontinuities identified by interpolating these data in a region between Golova and Susehri. The discontinuities are shown to be linked to negative flower structures formed within the strike-slip fault zone. Quickbird satellite images have been used to map faults and produce kinematic analyses which show that the active stress regime is dominantly strike-slip. However, normal faults and oblique-slip faults are also observed in the basin together with strike-slip faults and the stress regime creating the strike-slip faults is shown to have formed under NW-SE directed transtension. In addition, oblique faults formed under an extensional regime with NNE-SSW direction also occur in the Susehri Basin as subsets formed under the constraining strike-slip regime. We conclude that the Susehri Basin started to grow as a fault wedge basin following which it transformed into a pull-apart basin by a south splay on the NAFZ so it is now dominantly a transtensional pull-apart feature.
