46 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 10 / 46
Yayın Akdağ Kütlesi’nde (Batı Toroslar) Pleistosen buzullaşmalarının jeomorfolojik özellikleri ve optik uyarmalı lüminesans (OSL) ile yaşlandırılması(Türk Coğrafya Kurumu, 2017) Bayrakdar, Cihan; Güneç Kıyak, Nafiye; Turoğlu, Hüseyin; Öztürk, Tuğba; Canel, TimurBatı Torosların en yüksek ikinci zirvesine (Uyluk T. 3014 m) sahip olan Akdağ, batıda Eşen Ovası (60 m) doğuda Elmalı Ovası (1100 m) arasında yer alan ve 2700 m üzerinde birçok zirve barındıran, çevresine göre oldukça yüksek bir kütle görünümündedir. Akdağ Kütlesi'nde Kuvaterner'de meydana gelen buzul şekillerini incelemek ve OSL ile tarihlendirmek çalışmanın temel amacıdır. Bu çalışmada coğrafi bilgi sistemleri ve morfometrik analizler, OSL tarihlendirme yöntemi ve sedimantolojik analizlerden faydalanılmıştır. Akdağ Kütlesi'nin jeomorfolojik gelişiminde birden fazla etken ve sürecin rolü olmuştur. Bu süreçlerin başında karst, buzul, tektonik ve flüviyal gelmektedir. Akdağ Kütlesi'nde etkili olan Pleistosen buzullaşmaları, büyük ölçüde karstik yapıya uyumlu gelişmiş ve 2500 m ve üzerindeki paleo-karstik depresyonlarda kalın plato buzulları oluşmuştur. Akdağ Kütlesi'nde üçü büyük, beş buzul vadisi tespit edilmiştir. Bu buzul vadileri gelişmiş sirklerle başlayıp 2500 m seviyelerinde paleokarstik depresyonlara uyumlu olarak düşük eğimli, geniştabanlı ve büyük ölçüde taban ve yanal morenleri ile kaplı iken 2500 m seviyelerinden sonra vadiler daralıp klasik tekne vadi formu alıp 2000 m seviyelerinde cephe morenleri ile sonlanırlar. Akdağ Kütlesi'nde morenlerden alınan örneklere ait OSL tarihlendirmelerinde 17-21 bin yaşları çıkmıştır ki bu da son buzul dönemi MIS 2 ye denk gelmektedir.Yayın A new late holocene eolianite record from Altinkum Beach, North Cyprus(Scientific technical research council Turkey-Tubitak, 2012-06) Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Ertek, Topçu AhmetIn this study, we investigated the main depositional characteristics and obtained Optically Stimulated Luminescence (OSL) ages of coastal eolianite on the north coast of Cyprus, where this occurrence had not previously been recorded. Based on EDX/SEM and XRD data and field observations, the studied eolianite that crops out between elevations of 1 m and 14 m a.s.l. is made up predominantly of quartz grains, most of which consist of medium- to fine-grained sand. The rock comprises aragonite, calcite and quartz with lesser amounts of bornite and hematite as accessory minerals. OSL ages indicated that the initial deposition of eolianite sands took place at 1.51 +/- 0.21 ka years ago.Yayın Quaternary uplift of the northern margin of the Central Anatolian Plateau: New OSL dates of fluvial and delta-terrace deposits of the Kizilirmak River, Black Sea coast, Turkey(Pergamon-Elsevier Science Ltd, 2018-12-01) Berndt, Christopher; Yıldırım, Cengiz; Çiner, Tahsin Attila; Strecker, Manfred R.; Ertunç, Gülgün; Sarıkaya, Mehmet Akif; Özcan, Orkan; Öztürk, Tuğba; Güneç Kıyak, NafiyeWe analysed the interplay between coastal uplift, sea level change in the Black Sea, and incision of the Kizilirmak River in northern Turkey. These processes have created multiple co-genetic fluvial and marine terrace sequences that serve as excellent strain markers to assess the ongoing evolution of the Pontide orogenic wedge and the growth of the northern margin of the Central Anatolian Plateau. We used high-resolution topographic data, OSL ages, and published information on past sea levels to analyse the spatiotemporal evolution of these terraces; we derived a regional uplift model for the northward advancing orogenic wedge that supports the notion of laterally variable uplift rates along the flanks of the Pontides. The best-fit uplift model defines a constant long-term uplift rate of 0.28 +/- 0.07 m/ka for the last 545 ka. This model explains the evolution of the terrace sequence in light of active tectonic processes and superposed cycles of climate-controlled sea-level change. Our new data reveal regional uplift characteristics that are comparable to the inner sectors of the Central Pontides; accordingly, the rate of uplift diminishes with increasing distance from the main strand of the restraining bend of the North Anatolian Fault Zone (NAFZ). This spatial relationship between the regional impact of the restraining bend of the NAFZ and uplift of the Pontide wedge thus suggests a strong link between the activity of the NAFZ, deformation and uplift in the Pontide orogenic wedge, and the sustained lateral growth of the Central Anatolian Plateau flank.Yayın Dating fossil root cast (Black Sea coast, Turkey) using thermoluminescence: Implications for windblown drift of shelf carbonates during MIS 2(Elsevier Ltd., 2016-05-16) Polymeris, George S.; Kitis, George; Güneç Kıyak, Nafiye; Theodosoglou, Eleni; Tsirliganis, Nestor C.; Ertek, Topçu Ahmet; Erginal, Ahmet EvrenRhizoliths are mostly sub-aerially exposed root prints which appear through removal of the rock units that cap them. A horizontal-lying residual of a rhizolith, consisting purely of soft inner core material of white color was recovered 10 km west of Şile, Istanbul, in northwest Turkey within laminated oolithic massive aeolianite. The inner part, consisting purely of calcium carbonate, was dated by applying thermoluminescence, while for the outer shelves optically stimulated luminescence of quartz was used for age assessment. The age of the CaCO3 infill occupying the original place of the decayed plant roots was found to be 26.8 (±5.0) ka, corresponding to MIS 2. When compared with the ages of the middle (105.2 ± 15.6 ka) and outer (127 ± 9 ka) layers, corresponding to the later stage of MIS 5e or early stage of MIS 5d, the inner core coincides with the last glacial period when the sea-level was lower than the present, promoting transportation of ooids by offshore winds in conjunction with the exposed shelf carbonates. Based on the results yielded, rhizolith is much younger than the host rock aeolianite and witnesses to last glacial sea level lowstand when removal of shelf carbonates by offshore winds was promoted from the exposed shallow shelf plain. The results provide strong evidence that rhizoliths may not be coeval with the aeolianites within which they are embedded.Yayın A Preliminary note on depositional characteristics and optical luminescence age of a marine terrace, strait of Canakkale, Turkey(Coastal Education & Research Foundation, 2013-01) Avcıoğlu, Mustafa; Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Kapan Yeşilyurt, Sevinç; Yiğitbaş, ErdinçThis preliminary study investigated the depositional features and optical luminescence age of marine terrace sediments located on the east coast of the Strait of Canakkale, Turkey. With regard to depositional setting, the studied sequence is formed mostly of shallow marine deposits rich in quartz and oysters as well as other accessory minerals and various fossil sea shells. In vertical section, the sequence is characterized by two different stratigraphic units, i.e. a 1.50-m-thick sandy to gravely bottom unit (unit A) and an overlying 2.5-m-thick fossiliferous zone (unit B). On the basis of optically stimulated luminescence (OSL) age estimations obtained from six sampling levels from bottom to top, we determined superimposed cycles of deposition during interglacials from 246.47 +/- 25.32 ka (unit A) at MIS 7 to 127.48 +/- 8.91 ka (unit B) at MIS 5.Yayın The correlation of fast OSL component with the TL peak at 325 degrees C in quartz of various origins(Elsevier Science BV, 2010-02) Kitis, George; Güneç Kıyak, Nafiye; Polymeris, George S.; Tsirliganis, Nestor C.The fast component of the optically stimulated luminescence (OSL) signal in quartz is the basic tool for the optical dating. Its relation with the thermoluminescence (TL) glow-peak at about 325 degrees C is well established for naturally irradiated quartz. This relationship is also an important part of a general model for quartz on which many theoretical simulations of various OSL experimental results have been based. In the present work this relationship is systematically investigated in nine quartz samples of different origin. The linearly modulated OSL (LM-OSL) curves of all quartz samples for stimulation time less than 50s consists of two components discriminated easily by a computerized curve deconvolution (CCD) analysis. By comparing the un-bleached to the respective bleached TL glow-curve, it is found that the system of these two fast OSL components is directly related with only a small portion of the electron traps responsible for the TL glow-peaks in the temperature region 200-400 degrees C. By increasing the stimulation times, besides the two fast components, the medium and the slow components are also obtained. The medium and slow components are clearly related with the main body of the electron traps responsible for TL glow-peaks in the same temperature region 200-400 degrees C. Despite their different origin all quartz samples show an appreciable homogeneity concerning the number and time position of the individual components, whereas, the relative TL/OSL intensities vary strongly from sample to sample with the integrated TL intensity being generally much less than the integrated OSL intensity.Yayın Component resolved OSL dose response and sensitization of various sedimentary quartz samples(Elsevier Ltd, 2007-02) Güneç Kıyak, Nafiye; Polymeris, George S.; Kitis, GeorgeThe structure of the linearly modulated optically stimulated luminescence (LM-OSL) signal was studied for four sedimentary quartz samples, collected from different sites around Istanbul, Turkey. Applying a computerized deconvolution analysis to the LM-OSL curves, at least six individual components of first-order kinetics were identified and photoionization cross-section of each component was evaluated. The OSL dose-response curve of each component for each quartz sample was obtained, showing a remarkable differentiation from component to component. The behavior of a highly dosed sample to successive LM-OSL measurements was also studied showing a stable recuperation signal in the position of the "slow" and "medium" components and high resistance to OSL bleaching of the "slow" component. The individual sensitivity of each component as a function of the activation temperature was obtained. The sensitivity of each component was normalized over the respective sensitivity of the glow-peak at 110 degrees C of quartz in order to investigate the ability of the 110 degrees C glow-peak to act as a correction factor for all components of the LM-OSL curves examined.Yayın Optically stimulated luminescence to date coastel dunes and a possible tsunami layer on the Kavak Delta (Saros Gulf, NW Turkey)(Scientific Technical Research Council Turkey-Tubitak, 2009-01-21) Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Özcan, HasanOptically stimulated luminescence (OSL) dating was used to determine the timing of initial dune formation and reconstruct the evolution of coastal dunes that developed on the Kavak Delta, Saros Gulf, Turkey. Along a 500-mlong representative transect, dune sands were extracted from foredune, semistable (grey) dune, stable (dark) dune and dune-swamp boundary defined by a scarp 50?75 cm high. The data obtained showed that dune drift initiated 670 years ago. A pumice layer 15?20-cm-thick interbedded with marine clay and sand showed an OSL age of 340 years coinciding with underlying dune sand. XRF analysis showed that pumices were of similar composition to those erupted by plinian activity of Thera (Santorini) in 1628 BC. On the basis of OSL ages, these deposits, which are widely distributed on the western Anatolian coasts of Turkey, might have presumably transported landward along tide channels on the delta during a tsunami event that occurred in 1672 near Bozcaada and Kos islands according to tsunami history of the Aegean Sea.Yayın A comparative morphological, compositional and tl study of tenedos (Bozcaada) and Sile aeolianites, Turkey(Univ Agean, 2012) Polymeris, George S.; Erginal, Ahmet Evren; Güneç Kıyak, NafiyeAeolianites are carbonate-cemented deposits of coastal dune sands, mostly of Quaternary age. Even though aeolianite exposures on the coasts of the Mediterranean Sea are frequent, very few records have been documented from the coasts of either the Aegean or the Black Sea. The present study deals with evaluating and comparing both compositions and thermoluminescence (TL) ages of two recently reported samples of coastal aeolianites. Both were recovered at the Turkish coasts of Tenedos (Bozcaada) island, Aegean Sea and Şile, Western Black Sea. In the latter case, being the first record for the specific coastal area, the oldest age obtained was dated at 158±25 ka while the youngest age yielded was 108±14 ka. These values imply that both deposition and cementation occurred during the high sea stand of marine isotope stage 5 (MIS 5). In the case of Tenedos, the aeolianites were deposited between the early stage of the oxygen isotope stage 2 period (OIS 2) and the very late phase of the oxygen isotope stage 3 period (OIS 3). These latter TL results are in excellent agreement with a previous study of the same complex after applying OSL. Besides the ages, a number of luminescent features and properties in conjunction with compositional data suggest the dissimilarity for the quartz samples extracted from the aeolianites recovered at these two sampling sites, excluding thus any transport from one sampling site to the other, despite the short distance of the two sampling sites and the meteorological data regarding the preferable wind directions between them.Yayın Cement fabrics and optical luminescence ages of beachrock, North Cyprus: Implications for Holocene sea-level changes(Elsevier Ltd., 2016-05-16) Öztürk, Muhammed Zeynel; Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Öztürk, TuğbaCaCO3-cemented beachrocks are widely found along the northern coast of Cyprus. In this study, we aim to discuss the cementation history of beachrocks at ten particular sites within the context of Holocene sea-level changes. Cement fabrics, petrographic and geochemical characteristics, and optically-stimulated luminescence ages of buried quartz grains were studied. The seaward-inclined (~5-10°) parallel-stratified beds are composed mostly of sandstone alternating with conglomerate. Ooids, benthic and planktic foraminifera, bioclasts of red algae, echinoid spines and gastropods make up a significant proportion of the cemented beds. With CaCO3 content ranging between 37% and 65%, poorly-sorted grains are bonded by four distinct cements: circumgranular micritic coatings, sparry calcite infillings, pore fills, and meniscus bridges. This consecutive nature of cementation is typical of a marine phreatic and meteoric vadose environment when the sea level was lower than present but had a tendency to increase during middle to late Holocene. OSL ages ranging from 5.4 ka to 0.38 ka indicate that the deposition and ensuing cementation of the quartz grains occurred during two main stages; younger beds dated between 2.3 ka and 0.38 ka and older beds from 2.3 ka to 5.4 ka. A period devoid of beachrock formation was attested between 3.5 ka and 2.3 ka.
