AYBE- Katı Yer Bilimleri Lisansüstü Programı - Yüksek Lisans

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Çıkarma tarihi ile AYBE- Katı Yer Bilimleri Lisansüstü Programı - Yüksek Lisans'a göz atma

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  • Öge
    Yer Radarı İle Karstik Boşluk Araştırmaları
    (Avrasya Yerbilimleri Enstitüsü, 2015-10-20) Tuzer, Mehmet ; Çakır, Ziyadin ; 601121002 ; Katı Yer Bilimleri Anabilim Dalı ; Solid Earth Sciences
    Bu çalışmada karbonatlı kayaçların hakim olduğu Konya ilinin Ilgın ilçesinde karstik boşlukların araştırılmasına yönelik yer radarı ölçümleri yapılmıştır. Yer radarı yöntemi, yüksek frekanslı elektromanyetik prensip ile çalışan sığ jeofizik araştırma yöntemlerinden biridir. Teknolojik gelişmelerle birlikte kullanım alanı da genişleyen yer radarı, jeolojik, arkeolojik ve diğer birçok araştırma alanında kullanılmaya başlanmıştır. Karstik bölgelerde insan sağlığı ve jeoteknik açıdan tehlike barındıran bu boşlukların tespiti ile söz konusu alanlara yapılacak mühendislik yapılarının planlaması daha doğru olarak yapılabilmektedir. Bu alanlarda oluşturulacak yapılar yer altında bulunan boşluklarda gerçekleşebilecek çökmeler neticesinde ciddi hasar alma ihtimaline sahiptir. Bu nedenle karstik boşlukların oluşum şekillerinin ve yer altındaki uzanımlarının dikkatle araştırılması gerekmektedir. Yer radarının kolay uygulanabilen bir yöntem olması ve kısa zamanda geniş alanlar tarayabilmesi, bu gibi araştırmalarda yoğun olarak kullanılmasını sağlamaktadır. Çalışma sahasında 100 MHz'lik merkez frekansa sahip anten kullanarak toplamda uzunluğu 7.3 km'yi derinliği 5 m'yi bulan profil verisi elde edilmiştir. Daha önceki çalışmalar dikkate alınarak, çeşitli aşamalardan oluşan veri işlem sonuçları karşılaştırılmalı olarak değerlendirilerek en uygun veri işlem yöntemi belirlenmiştir. Elde edilen radargramlardan toplam uzunluğu 350 metreyi bulan dört tanesi seçilerek yorumlanmış ve boşluklu, çatlaklı ve deformasyonlu bölgeler belirlenmiştir. Yorumlanan verilerde detaylı olarak polarizasyon analizi ve genlik analizi yapılmıştır. Boşluk olan yapılar belirlenerek empedans değerleri üzerinden birbirleriyle olan ilişkileri ortaya konmuştur. Elde edilen sonuçlar bölgede mevcut sondaj ve jeoloji verilerinin ışığı altında değerlendirilerek karstik yapıların modellemesi yapılmıştır. Radargramlarda yorumlanan anomalilerin parametreleri hesaplanarak önce basit modelleme ardından da karmaşık modelleme yapılmıştır. Modelleme sonuçları da radargramlarda yapılan analizleri desteklemektedir. Bu tez çalışması ile karstik bölgelerde yer radarı verilerinin işlenmesinde izlenilecek yaklaşımların belirlenmesi, elde edilen radargramların yorumlanması ve modellenmesi konusunda bilgiler sunan bir kaynak ortaya konulmuştur.
  • Öge
    Dynamic Modelling Of Back-arc Extension İs The Aegean Sea And Western Anatolia
    (Eurasia Institute of Earth Sciences, 2016-05-02) Mazlum, Ziya ; Göğüş, Oğuz Hakan ; 602141002 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    The Aegean Sea/Western Anatolia back-arc has predominantly been extending due to the southward retreat of the Hellenic subduction zone. This extension has been inferrred by the widespread magmatism, detachment faulting and the exhumation of metamorphic core complexes. While there is an agreement that the active slab retreat has been producing the extension in this back-arc (since the late Oligoce-early Miocene), the real nature of this extension may also be due to the other geodynamic mechanisms (e.g post-orogenic thinning). The major objective of this thesis is to test the geodynamic evolution of the back-arc extension by using numerical modelling and reconcile the model results with the observations from the Aegean Sea and Western Anatolia. Aegean Sea and Western Anatolia were under influence of collision between Sakarya continent and Menderes Taurides until Paleocene. The terminal closure of Northern branch of Neotethys compressed the area and it is thought that crust and lithosphere should have thickened. When the compression is worn of, the whole Aegean region started to extend. The large scale extension has been inferred by the exhumation of metamorphic core complexes (e.g., Kazdağ and Menderes massifs) and detachment faulting since late Oligocene. Interpretations of petrological data from the volcanic units show that the first arc volcanism, associated with the Hellenic subduction zone begun at Rhodope massif during the late Oligocene, and migrated towards SW. The problem is, while the Aegean Sea has possibly extended more than western Anatolia and lowered the topography < 0, the Western Anatolia has an average 1 km elevation above sea level It is possible that the various geodynamic reconfigurations may have been effective in differing the geological evolution of these two regions. For instance, it has been suggested that the slab tear/break-off affect the Western Anatolia inferred by the seismic tomography images. For modelling work, a geodynamic code named "SOPALE" that solves creeping flow for viscoplastic environment was used. A starting model was determined and some parameters were changed in order to understand their effects. Starting model was a simple subduction model with a thick continental lithosphere (40 km crust, 110 km mantle lithsophere) and a thinner oceanic lithosphere (100 km). The oceanic lithosphere was pushed with 1cm/year velocity in order to create a subduction. According to model results, trench was migrated 220 km to the south and crust was thinned down to 28 km. The back-arc topography was subsided 1.5 km. In order to understand the effects of both trench retreat and breakoff, tests for continous slab retreat for Aegean Sea, and discontinous subducting slab or "tear" for Western Anatolia has been conducted. For continous slab retreat, the oceanic lithosphere thickness, density, continental lithosphere thickness and moho temperatures of the back-arc have been changed. Models with different oceanic lithosphere thickness revealed that thicker oceanic lithosphere produced more extension at the back-arc. While 70 km thick oceanic lithosphere is used, slab was retreated 180 km and crust was thinned down to 32 km. But if the lithosphere thickness is increased to 110 km, the total amount of retreat was calculated 260 km and crust was thinned down to 26.5 km. Thicker lithosphere is heavier and produces more slab pull force that required for slab retreat. Likewise models with different oceanic lithosphere densities shown that denser material increases extension at back- arc. If density of oceanic material is selected 3290 kg/m3, the slab migrates 30 km and crustal thickness was calculated 37 km. In spite of that, if the material density is selected 3340 kg/m3, slab retreated 200 km and crustal thickness is decreased to 30 km. The important thing here is the density difference between lithosphere and asthenosphere. Asthenosphere density was selected as 3280 kg/m3. Bigger density difference produces more slab pull force and accordingly more extension. One other important factor is the thickness of the back-arc lithsophere. According to models, thinner continental lithosphere supports back-arc extension. If 90 km thick continent (40 crust, 50 mantle lithosphere) is selected, slab retreat increased to 350 km and crust of the back-arc thinned down to 24 km. On the other hand, model with 130 km back-arc lithosphere (40 km crust, 90 km mantle lithosphere) indicate that amount of slab retreat decreased to 280 km and crustal thickness to 27 km. That means that the thinner back-arc lithosphere may deform easily and contributes slab retreat related extension. Previous studies indicate that lithosphere of the region may have thinned down via convective removal or delamination. Different from Aegean Sea, experiments with discontious slabs or "tears" were conducted for Western Anatolia. To demonstrate the slab break-off, weak and dense material was used for the edge of the slab. According to tomography images, the slab is still under SW Anatolia, so break-off event has to be recent. Our models show that slab break-off is not so significant in terms of extension. Continental lithosphere thickness seems more important to understand the geodynamic properties of the region. If Paleocene compression affected the lithosphere of Western Anatolia more than than the lithsophere of Aegean Sea, there should be an thickness difference between these two. Continental lithsophere thickness models indicate that thicker overriding plate is less likely to extend, so there should be a shear zone within the subducting slab. The tear within the slab evolved at this counterclockwise shear zone. According to this interpretation, slab tear is not a cause, its an effect. Volcanism data also show that Isparta volcanics (where the tear is found) has age of 6-4 million yeas, corresponds to tear event. Slab break-off models show the remnant of the slab still sinking beneath asthenosphere just like the tomography images.
  • Öge
    Geodynamic Modeling The Styles Of Lithospheric Delamination With Application To The Eastern Anatolia
    (Eurasia Institute of Earth Sciences, 2016-08-01) Memiş, Ömer Caner ; Göğüş, Oğuz Hakan ; 602131001 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    The East Anatolia High Plateau is a young and active collision zone and also known as a part of Alp-Himalaya orogenesis belt. The east Anatolian High Plateau has been rised by the continental collision of the Arabian plate to the south towards Eurasian plate to the north. by continental collision (13 ma). Former studies suggest that during the convergence motion of Arabian plate, the lithosphere shortened and thickened beneath the East Anatolia and regional topography isostatically compensated by its thick lithosphere. However, recent deep geophysical studies show that regional topography being compensated by hot and convective asthenosphere instead of thick lithosphere and the most of plateau devoid of its mantle lithosphere. Petrological studies address that the first volcanic products in Erzurum-Kars plateau (13ma) characterized by an asthenospheric origin. Corroborating geophysical and geophysical findings, the geodynamic evolution of the plateau accounted by hypothesis of slab steepening and following break-off. According to this hypothesis, being subducted Neotethys's oceanic mantle lithosphere benath the Eastern Pontides has been decoupled from overlying accreted prism and afterward its broke-off. This hypothesis occurs similar to delamination theory which is introduced by Peter Bird (1979) for uplift of Colorado Plateau. In this work, by using 2D numerical modeling method, we test lithospheric delamination model by changing rheological, physical and mechanical parameters. Also, we investigated the effects of lower crustal rheology, mantle lithosphere plastic yield stress, mantle lithosphere density, plate convergence rate and crustal thickness on delamination processes. Model results show that the evolution of lithospheric delamination is optimum when the lower crustal rheology selected as felsic granulite. On the other hand, break-off event occurs dependent on mantle lithosphere plastic yield stress and plate convergence rate. The break-off events occurs earlier when the mantle lithosphere plastic yield stress value kept low (<75 MPa) compare to models in which used higher mantle lithosphere plastic yield stress. Furthermore, increasing plate convergence rates has a big role on rising of topography and thickening of crust, however, it has a negative effect on slab break-off. We were not observed break-off event at higher plate convergence rates (>2 cm/yr). The model results reconciled against observations in the eastern Anatolia and by selecting the most viable models we argued that conformity of the proposed model for regional geodynamic evolution.
  • Öge
    Paleoenvironmental İnterpretations For Kizilirmak Delta Plain Using Sedimentological Records, Multiproxy Analysis And Palynology 
    (Eurasia Institute of Earth Sciences, 2016-11-25) Ertunç, Gülgün ; Çiner, Tahsin Attila ; 601141009 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    The Kızılırmak Delta is the delta of the Kızılırmak River and it's located near the province of Samsun, Central Black Sea Region of northern Turkey (41◦30 to 41◦45' N, 35◦43' to 36◦08' E). The latest major transgression of the Black Sea is related to the glacial melting accompanied with a worldwide sea level rise. The eastern Kızılırmak Delta platform is thought to be a part of a post-glacially filled canyon system, which has been incised into the former delta platform during the last glacial. The sediment fill of canyon were supplied by the Kızılırmak River. A sediment core was obtained from possible location of filled canyon system in the eastern wetlands of Kızılırmak Delta Plain. High sedimentation rate of the Kızılırmak River provide a perfect archive and continious records of the environmental and climatic conditions for Quaternary. Lithological properties, multi proxy analysis and palynological analysis were carried out from recovered sediment core and age model executed using radiocarbon analysis. By combining several techniques together, a broader data was determined and cross-correlations are made to ensure an accurate paleoenvironment reconstruction of the Kızılırmak Delta. This thesis was carried out in the context of Anatolian pLateau climatE and Tectonic hazards (ALErT) project, funded and supported by the European Commission as part of the Marie-Curie-Initial Training Networks (ITN). Observations and multiproxy analysis are carried out at Istanbul Technical University (ITU), Eurasia Institute of Earth Sciences (EIES) and Eastern Mediterranean Centre for Oceanography and Limnology (EMCOL) laboratories. Palynological analysis is carried out in Faculty of Natural Sciences Department of Geology and Paleontology, Comenius University in Bratislava, Slovakia. The age model was constructed using AMS radiocarbon analysis in Beta Analytic Inc. North American Facilities. Four major lithostratigraphic units have been identified in the BW-1 core section, along with a number of sub-units. This study provides around 7300 year high-resolution sedimentological record of using a multi-proxy approach of a sediment core from the Kızılırmak Delta Plain. Despite the limitations of a single core our results obtained from several methodologies (sedimentology, geochemistry and palynology) provide insights in the paleoenvironmental conditions.
  • Öge
    Labranda Antik Kenti Yer Radarı Araştırması
    (Avrasya Yerbilimleri Enstitüsü, 2016-11-25) Yiğit, Fırat ; Tüysüz, Okan ; 602101001 ; Katı Yer Bilimleri Anabilim Dalı ; Solid Earth Sciences
    Bu çalışmada, arkeolojik bir sit alanı olan Labranda Antik Kenti'nde kazı çalışmalarına yardımcı olmak ve daha sonra yapılacak kazı çalışmalarını yönlendirmek amacıyla jeofizik bir yöntem olan Yer radarı çalışması yapılmıştır. Çalışma yapılacak alanlar önceden belirlenmiş, koordinatları alınmış ve Yer radarı çalışmasının yapılması için uygun hale getirilmiştir. Çalışma alanı 2 alana ayrılmış ve her iki alanda da yer radarı ölçümleri yapılmıştır. 1. Alanda profil aralıkları 0,25 metre, 2. Alanda profil aralıkları 0,5 metre olarak uygulanmıştır. Çalışmada GSSI SIR-3000 kontrol ünitesi ve 400 Mhz merkez frekanslı anten kullanılmıştır. 400 Mhz merkez frekanslı anten ile araştırma derinliği 3,5 metre olmuştur. Arazi çalışmaları sonucunda elde edilen hem veriler bilgisayar ortamına aktarılarak işlenmiştir. Veri işlem aşamaları için ReflexW programı kullanılmıştır. Program üzerinde dewow, muting, statik düzeltme, enerji geri kazanımı, arkaplan gürültüsünün süzgeçlenmesi, bant geçişli süzgeçleme, f-k süzgeçleme aşamaları uygulanmıştır. İşlenmiş veriler yine ReflexW programı ile kat haritaları oluşturmak için düzenlenmiştir. Kat haritaları üzerinde derinliklere bağlı olarak, yeraltındaki muhtemel yapılar incelenmiştir. Kat haritalarının değerlendirilmesi sonucunda elde edilen bulgular yorumlanmıştır. Yeraltında olası yapı kalıntılarına ve yıkılmış yapılara ait olabilecek yığıntılara rastlanılmıştır. Çalışmanın sonunda yapı kalıntıları ve yığıntılar harita üzerinde gösterilmiştir.
  • Öge
    Reconstruction Of The Paleoclimate On Dedegol Mountain With Paleoglacial Records And Numerical İce Flow Models 
    (Eurasia Institute of Earth Sciences, 2017-05-05) Candaş, Adem ; Sarıkaya, Mehmet Akif ; 602151009 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    The current glaciers in Anatolia have been gradually disappearing with the ongoing climate changes. There are geological proxies left behind from the ice, which is an indication of paleoclimate changes. It is known that the glaciers carry large amounts of sediments in their life cycles. After they retreat, these sediments remain where they were. They are called as moraine, which has been well preserved in some Anatolia mountains. In this study, the paleoglaciers that existed in the Late Quaternary period on the Dedegöl Mountain were reconstructed under the prescribed paleoclimatic conditions. The main idea is to recreate paleoglaciers under different climatic conditions; it is the recreation of the paleoclimate. This approach, in a sense, is aimed at understanding the past-term climate. Thus the proxies left behind by the glaciers have been used as an important proxy to estimate the paleoclimate conditions. Dedegöl Mountain is located within the boundaries of Konya and Isparta provinces. The maximum elevation of the mountain is 2997 m above the sea level. Beys ̧ehir Lake is located about 15 km to the east of the study area. 30 m × 30 m resolution digital elevation model of Dedegöl Mountain was used. The model domain is covering 37.5670 - 37.7237 North latitudes and 31.2100 - 31.3667 East longitudes. The model area is about 16.92 km × 16.92 km = 286 km2. Glacial mass balance was calculated with today's climatic conditions. Then the paleoclimate was modeled. A two-dimensional numerical glacier flow model was written in MATLAB to reconstruct the flow of glaciers under different paleoclimatic conditions. An open source glacier flow model software named Parallel Ice Sheet Model (PISM) was also used. The glacier valleys in the area are identified during two field studies in the summer months of 2015 and 2016. The Sayacak Glacial Valley on the north, the Elmadere Glacial Valley on the east, the Muslu and Karagöl and the Karçukuru Glacier Valleys in the south and the Kisbe Glacial Valley in the north-west were studied. The moraine crests positions were identified and paleoglacier boundaries were determined. Then, paleoclimatic conditions of that fit the modeled glacier extent were determined. Positive Degree Days approach was used to calculate the ablation of a glacial. This approach is briefly based on the idea that there is a correlation between the sum of all the temperatures above the melting point and melting of snow (or ice) at the same location over a year. A decrease in glacial mass occurs for days with a temperature higher than 2°C. In the calculation of the accumulation mass, the amount of precipitation in the area is used. If the precipitation occurs at a temperature higher than 0°C degrees, all precipitation occurs as rain. The accumulation linearly increases between 2 and 0°C and it contributes to the annual mass balance. The precipitation is considered to be entirely snow below 0°C air temperature. Therefore, glacier's annual budget is based on the difference between accumulation and ablation. It is thus possible to establish a direct relationship between the amount of ice in a particular area and climate conditions. In these calculations, factors such as surface energy mass, the cloudiness, and the wind effect can be also used, but these factors are not included in this study. Previous studies in the region have indicated that paleoclimate was cooler and wetter than present-day climate during the Last Glacial Maximum period. It is stated that the temperatures were 8 to 11°C lower than today, with the precipitation being 20% higher. In this study, temperatures in the model of paleoglaciers were decreased by 8, 9, and 10°C. Precipitation values were increased by 0%, 25% and 50% than today. The best way as a glacial flow model is to solve the Full Stokes equations. However, the solution of these equations is not efficient in terms of processor requirements and time. Different models have been developed for the flow of glaciers moving. In this work, open source software named Parallel Ice Sheet Model (PISM) was used. However, a two-dimensional time-dependent glacial flow model has also been developed. The results obtained in these two models were discussed. PISM uses the netCDF file type as input. In this file, data such as temperature, precipitation, glacial thickness were stored. Within the scope of the thesis, a code was developed to provide appropriate data input for PISM. This code calculates the glacial mass balance under the paleoclimatic conditions and then transforms this data into an input for PISM. The results obtained from the study include: (1) although the Parallel Ice Sheet Model (PISM) has been developed for modeling larger-scale ice sheets, it is proved it can be also used as a model for valley glaciers, such as Dedegöl Glacier Valleys (2) a temperature depression between 10°C with an increase in precipitation of 25%, and 9°C with 25% for LGM and Early Holocene respectively, (3) existing digital elevation data used in the models may cause some degradation of glacier reconstruction because they contain moraine deposits of different glacial periods, (4) the results obtained from the models indicate that the moraine deposits formed at different times should be evaluated with different climatic conditions. There are various sources of uncertainty in the model. Firstly, the resolution of the climate models is 570 m. The digital elevation model resolution is 30 m, so this dismatching can create some uncertainty. However, sudden elevation changes in the digital elevation model can lead to high slopes. From the past, it can be assumed that the boundaries of the changing structure with erosional processes created uncertainty. Moreover, seasonal fluctuations in climate data can create uncertainty in the model. In further studies, the removal of the moraine deposits to reconstruct the digital elevation model will positively affect the ice flow. This is because these obstacles prevent the glaciers to advance to the past moraines. The glacier flow and climate models applied in this study can be used in other paleoglacial areas in the region which can increase the proxy data about Turkey's paleoclimatic conditions.
  • Öge
    Late Quaternary Glaciations And Cosmogenic 36cl Geochronology Of Mount Dedegöl 
    (Eurasia Institute of Earth Sciences, 2017-05-05) Köse, Oğuzhan ; Sarıkaya, Mehmet Akif ; 602151001 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    Recent years experienced a significant advance in the glacial geochronology of the Turkish mountains. These studies suggested that major glacial advances were occurred in the Late Pleistocene and partly in Holocene. Maximum extent of MIS-2 (Marine Isotope Stage) glaciers happened during the Last Glacial Maximum (LGM, i.e. 21 ka ago). Glaciers were as large as 6 km in length in some mountains. The extend and timing of paleoglaciers on the northern side of the Dedegöl Mountain (37.64oN, 31.27oE, 2992 m), on the western Taurus Range, was not known. Zahno et al (2009) used cosmogenic surface exposure dating method with cosmogenic 10Be and 26Al to date a glacier expansion out of the Muslu Valley, located on the eastern part of the Mount Dedegöl. They dated to maximum extent of paleo-glaciers to 24.3±1.8 ka ago and gave evidence for pronounced glacier advances prior to the global Last Glacial Maximum (LGM). According to Zahno et al (2009), the glacier retreated which driven by climatically was no later than 17.7±1.4 ka ago. Çılğın (2015) used OSL (Optically stimulated Luminescence) dating method to date the moraines in Mount Dedegöl. OSL age results revealed that at least two glacial stages occurred during late Pleistocene in the Mount Dedegöl. In this study, I focused on geomorphological evidence of the Quaternary glaciers on the northern valleys of Mount Dedegöl. The main goal of this study was to determine the glacial geomorphology and obtain the landform ages of glacial deposits of northern Mount Dedegöl. Therefore, to achieve these goals geomorphological maps of the study area were first prepared. Later, rock samples from moraines were taken for cosmogenic surface exposure dating. Main glacial valleys and moraine borders were positioned using the GPS. Both erosional and accumulation landforms such as lateral moraines and cirques formed by glaciers were determined. These landforms were sketched with direct observation to analyze the surface morphologies. The height, length and width properties of the moraines and sample locations noted during the field studies. After the field studies, the data obtained from the field and from the GIS database structure were compared and produced the final glacial geomorphological maps in GIS software (ArcMap 10.3). Based on digital cartographic symbols, sample locations, all moraine types, cirques, and other glacial landforms were drawn for each glacial valley. The cosmogenic 36Cl dating method was used in the Mount Dedegöl in order to determine the surface exposure ages of moraines. In this way, the length of time that any rock has been exposed to the cosmic radiation can be estimated. Samples for cosmogenic 36Cl dating were collected from the top of the boulders on the crest of the moraines. A hammer and chisel were used to take samples from upper few centimeters of the boulders. The boulders were selected according to their positions. Boulders were sampled based on their appearance, size, preservation and position on the crest. Stable boulders with strong roots in the moraine matrix were preferred. The sample preparation of collected rock samples was done in order to measure minute amount of cosmogenic 36Cl in rocks by AMS (Accelerated Mass Spectrometer). The laboratory methods consist of four preparation stages: (1) crushing, grinding and sieving, (2) leaching and digestion, (3) chemical separation and (4) target preparation. Final target samples prepared at ITU/Kozmo-Lab in İstanbul were taken to ASTER AMS lab, France (The French National Facility, CEREGE, Aix en Provence). Surface exposure of the samples were measured by the 36Cl Exposure Age Calculator v2.0 (http://cronus.cosmogenicnuclides.rocks/2.0/html/cl/). Rock samples were collected from a total of 20 boulders in the Mount Dedegöl. There were eight samples in Sayacak Valley, five samples in the Kisbe Valley and seven samples in Karagöl Valley in total. Cosmogenic 36Cl ages obtained from the moraines on Mount Dedegöl have contributed new information to glacial geochronology of Turkey. Twenty boulders from moraines in three glacial valleys of the Mount Dedegöl were dated by 36Cl surface exposure dating. Moraine ages from the Mount Dedegöl indicates that there are three glacial stages identified by dating of 20 samples. Pre-LGM moraines, 29.1 ± 1.7 ka and Early Holocene moraines 10.9 ± 0.8 ka were deposited in Sayacak Valley. In Karagöl Valley, LG (Late Glacial), 13.5 ± 0.7 ka and 16.4 ± 1.1 ka were deposited. There are only Early Holocene moraines, 11.6 ± 0.7 ka were identified in Kisbe Valleys. Surface exposure ages with cosmogenic 36Cl reveal that there is no glacier retreat earlier than 32.4 ± 3.3 ka ago in the Mount Dedegöl. The oldest age obtained from hummocky moraines in the Sayacak Valley give substantial evidence about ice accumulation prior to the global LGM (21 ± 2 ka). Pre-LGM ages from hummocky moraines in the Sayacak Valley are 24.6 ± 2.3 ka, 32.4 ± 3.3 and 30.3 ± 3.2 ka ago. Consequently, the timing of maximum glaciation on Mount Dedegöl can be considered as the average of both ages which is 29.1 ± 1.7 ka. The youngest glacial stage occured during the Early Holocene in the mount Dedegöl. There are only Early Holocene moraines were identified in Kisbe Valleys with ages 11.6 ± 0.7 ka. In Sayacak Early Holocene ages are obtained from right lateral moraine (10.9 ± 0.8 ka). Late Glacial moraines in the Karagöl Valley are well preserved. In Karagöl Valley, a terminal moraine was dated to 15.6 ± 1.4 ka to 17.2 ± 1.7 ka ago. Thus, it can be considered that Late Glacial glaciation in Karagöl valley occured 16.4 ± 1.1 ka ago, which is the avarage age of the terminal moraine ages.
  • Öge
    Distribution Of Quaternary Deformation Along The Coasts Of Cyprus, İnferences From Marine Terraces
    (Eurasia Institute of Earth Sciences, 2018-05-08) Altınbaş, Cevza Damla ; Yıldırım, Cengiz ; 602141005 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    Cyprus is located on the subduction zone between African and Eurasia Plates. The topography of the island is a result of distributed deformation associated with the subduction related processes in the south of the Eurasia Plate. Trodos and Kyrenia mountains are major morphotectonic units that integrally tied to plate boundary deformations. The presence of uplifted marine terraces is piece of evidence of subduction related active deformation in the part of the island. To understand rate and pattern of deformation, I conducted geomorphic mapping of marine terraces by ArcGIS and analyzing of paleo-cliffs by TerraceM Matlab based program. As a result of these analyzes I calculated the uplift rates with reference to MIS 5. Here will present morphotectonic implications from temporal and spatial distribution of marine terraces along the Cyprus.
  • Öge
    Determination Of Last Glacial Equilibrium Line Altitudes Of Turkey By Glacial Mass Balance Model
    (Eurasia Institute of Earth Sciences, 2018-06-28) Gündüz, Savaş ; Sarıkaya, Mehmet Akif ; 602161006 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    Turkey is located in the Eastern part of Mediterranean region between 36°N and 42°N latitude and 26°E and 45°E longitude. Turkey's climatic and topographic features have strong contrasts which indicate a characteristic feature for Turkey. As a general view, Turkey has a varied topography for its all geographical regions. Turkey is a mid-latitude country located with a relatively high topography. In the current climate of Turkey, glaciers do not occupy large areas but it is known that paleo-glaciers covered larger areas during the Last Glacial stage based on earlier studies. There is a close relationship between climate and equilibrium line altitude (ELA) of a glacier. Glaciers are the most commonly used indicators for climate change. The purpose of this study is to calculate Turkey's ELA by glacial mass balance model during the Last Glacial Maximum (LGM) and compare with previous studies. For this purpose, monthly present day temperature and precipitation were used to make paleo-climatic estimations. The Last Glacial stage ELA were determined by a glacier mass balance model and compared with previous studies. In total, 25 glacial areas have been studied. Using the monthly temperature and precipitation data obtained from WorldClim, annual ablation was calculated by positive degree day model and annual accumulation were calculated assuming that precipitation falls as snow at 0°C. Calculations made by an in-house Matlab program. Annual mass balances were found with the difference between the accumulation and ablation values. The simulations for the last glacial period were firstly done with the precipitation was kept the same as the present conditions, and the temperature depressions was changed between -8°C and -12°C. In the second case, the temperature was kept constant (-10°C lower than today), the precipitation was changed from drier (%25 drier) to humid (%25 wetter) conditions than today. Accordingly, the last glacial paleo-equilibrium line altitudes in Turkey were calculated and spatially compared with earlier studies. When temperature is 10°C cooler than today and precipitation is in the present day condition (Precipitation=1), ELA decreasing from south of Turkey to the north. It is almost between 2400- 2500 m a.s.l. in the Southeast Taurus. In Akdağ and Beydağ, ELA is more than 2200 m a.s.l in Sandıras, Davraz, Dedegöl, Geyikdağ, Aladağlar and Bolkar, ELA is about 2200 m. It has a decreasing pattern toward to north. Erciyes and Soğanlı Mountains have ELA 2000-2200 m. In Uludağ which is situated in the north part of the Turkey it is in between 1600-1800 m. In the eastern part of Turkey, ELA is higher when it compared with western Turkey. In Buzul and İkiyaka Mountains, ELA is in between 2600-2700 m. Southeast part of Turkey has the highest ELA value. For –10°C temperature decrease and same as today's precipitation values (from south to north) there is a decreasing pattern. It shows that there is clear latitude effect in Turkey's ELA. From west to east ELA is increasing as elevation 'increasing from west to east. It also shows that elevation affects the ELA in Turkey because elevation is increasing from west to east. The places where elevation is high have higher ELA compared to other places in the Turkey. According to the study of Messerli (1967), ELA is 2300 m in the Black Sea region. When the temperature -8 °C below today and present day precipitation condition, ELA estimates of 2000- 2100 m in the Black Sea close the Messerli's estimates. In the Mediterranean ELA is around 2500 m. For Mediterranean, all results that I have are higher than 2000 m. This can indicate ELA is almost same values in the Mediterranean in LGM. In the south east region that have most of the glaciers, ELA is between 2700-2800 m in the study of Messerli (1967). It is more than 2400-2500 m in southeast region for all the cases applied. That also shows that there is a match between these values. In the west part of Turkey, ELA is around 2300 m in Messerli (1967) study but in this part, I got lower ELA values when it compares to Messerli (1967)'s study.
  • Öge
    Tokat Masifi Kuzeyinin (Taşova-Ladik) Metamorfik Evrimi
    (Avrasya Yerbilimleri Enstitüsü, 2018-10-30) Atlı, Erbe Nur ; Topuz, Gültekin ; 602151003 ; Katı Yer Bilimleri Anabilim Dalı ; Solid Earth Sciences
    Bu tezin amacı, Tokat Masifinin en kuzeyinde yer alan Liyas-önecesi yaşlı kayaçların evrimini ortaya koymaktır. Bu amaç için başlıca Taşova ve Ladik bölgeleri seçilmiştir. Taşova bölgesinde Liyas öncesi birimler düşük dereceli metamorfitler ve Orta Permiyen yaşlı kireçtaşlarından oluşurken, Ladik bölgesinde ise yalnızca Orta Permiyen yaşlı kireçtaşlarından oluşmaktadır. Tokat Masifi, Taşova ilçesinde, başlıca metabazit, fillit, mermer, kalkfillit ve bu metamorfik kayaçların içerisinde ~2 km2'lik bir alanı kapsayan ve metamorfik olmayan kireçtaşı kitlesi tarafından temsil edilmektedir. Bu birlikteki metamorfik birimleryeşilşist-mavişist geçişli koşullarda başkalaşıma uğramıştır. Metamorfitler içindeki metabazitler okyanus adası bazalt-zenginleşmiş okyanus ortası sırtı bazalt niteliği sunmakta olup, olasılıkla okyanus içi deniz dağlarının (semount) eklenmiş parçalarını temsil etmektedir. Kayaç birlikteliği bakımından, Taşova kuzeyindeki metamorfik kayaçlar bir yığışım karmaşası niteliğindedir. Bu verilere göre, Tokat Masifi, Lavrasya kıtasının Permo-Triyas döneminde aktif güney kenarı boyunca bulunan Tetis Okyanusunun kapanması ile ilişkilidir. Bu özelliği ile Sakarya Zonu'ndaki, Karakaya Karmaşasının Nilüfer birimi ile deneştirilebir. Dolayısıyla Taşova yöresinde metamorfitler, daha doğuda bulunan Ağvanis metamorfitleri ve Pulur masifinin tabanındaki düşük dereceli birimin batıya doğru devamı niteliğindedir. Liyas önceki birimler arasındaki kireçtaşlarının her iki bölgede tabanı direk olarak gözlenmemektedir. Bu kireçtaşları bol miktarda Orta-Üst Permiyen (Vordiyen-Kapitaniyen) çağını karakterize eden Foraminifer fosili içermektedir. Yer bilimleri literaturunde genel itibarıyla bu kireçtaşlarının daha güneyde bulunan Gondvana kıtasından türemiş olduğu görüşü savunulmaktadır.
  • Öge
    Comparison Between Hydrostatic And Nonhydrostatic Simulations Of Turkish Strait System
    (Eurasia Institute of Earth Sciences, 2018-12-13) Parkan, Ece Nil ; Ilıcak, Mehmet ; 602161002 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    Turkish Strait System (TSS) consists of Dardanelle Strait, Marmara Sea and Bosporus Strait is a coupled system where the fully coupled effects are significantly different than three individual members of the system. Due to the deep inflow from Mediterranean Sea and also outflow of the Black Sea, Marmara Sea acts like a buffer zone of these two important water masses. In addition, the Marmara Sea has its own separate temperature and salinity water characteristics that is resulted in significantly different stratified layers than the neighbor seas. The more saline (38 psu) and warmer (26⁰C) waters from the Mediterranean Sea mixes with colder (22⁰C) and less saline (18 psu) Black Sea water in the Marmara Sea and creates cold intermediate layer (CIL) which is highly effected from surface fluxes that will change its thickness and depth from the surface. We employ a 3D hydrostatic and non-hydrostatic ocean general circulation model in this study. The hydrostatic simulation is carried out from Sanino et al, 2017, where they investigate the impact of volume fluxes on the TSS circulation. The initial conditions for the three different Seas are based on the measurements that are taken from the CTD's during the summer season. This initiliazed warm upper surface waters along basins, couldn't reach to climatological cold surface water of Black Sea without heat fluxes like in the other months of the year. Surface waters, summer time is the special case, are colder in general. (According to the SHOD(2009), Month of February Dardanelle Strait has temperature down to 8.6⁰C; and in the Bosprous Strait it is 4.5⁰C) On the other hand, boundary condition of the Aegean side of the domain, a problem seems to exist due to mesoscale eddies created and trapped because of the closed boundary conditions. However, we believe that this will not affect the Marmara basin because of short integration time length. Our aim to understand the performance of non-hydrostatic terms in mixing of exchange flows in TSS. In our control simulation, we find that there are four different layers in the temperature field in the Dardanelle Strait whereas in the Bosporus Strait, there are 3 layers seen as a result of density differences of two water distinct sources (Black Sea and Eagean Sea). In the salinity field of the Bosporus Strait, vertical mixing effect is observed close to the surface waters in which salinity concentration is decreased. The interfacial layer between surface and deep layers is also increasing in thickness towards the Bosporus Strait. Circulation in the Marmara Sea is effected dominantly from jet flux issued to the Sea of Marmara from Bosporus. Jet has three branches which splits into firstly to the west side of the Bosporus Strait, opening of the Izmit Bay, secondly to southern boundary of the Marmara Sea by bending and converging with the big gyre in the middle and lastly to the North. This Northern branch also splits into two; one which directly flows trough the northern side of the Marmara Island and combined with small scale eddy by increasing its circulation speed and the other branch is shooting into the Marmara islands. This extended part of the jet also splits into many branches and flows into the entrance to the Dardanelle Strait. In our non-hydrostatic simulation, we find that the differences between two simulations are minor in the deep at this resolution. Surprisingly, the largest differences are close to the surface in terms of circulation and mesoscale eddy processes. The main reason behind this difference is resolving the evolution of vorticity using the full 3D vertical acceleration term in the non-hydrostatic simulation.
  • Öge
    Metamorphic Evolution of the Elekdag Eclogites (Central Pontides)
    (Avrasya Yer Bilimleri Enstitüsü, 2019-01-13) Burlick, Theodore Douglas ; Topuz, Gültekin ; 602141003 ; Solid Earth Sciences ; Katı Yer Bilimleri
    The topic of the thesis is focused on the metamorphic and tectonic evolution of high-pressure metamorphic eclogites and by extension, the surrounding meta-lherzolite and serpentinite of the Elekdag Ophiolite within the Central Pontide Mountains of Turkey. The goal of this study is to continue the work of previous authors in better understanding the timing and conditions of metamorphism and their associated tectonic events through field mapping, detailed petrographic and microstructural analysis, investigation of stable equilibrium assemblages with wavelength-dispersive x-ray, energy-dispersive, angle-selective backscatter spectroscopies coupled with isochemical phase equilibria diagrams and conventional cation exchange geothermobarometry analysis. The Elekdag Ophiolite and other related ophiolites in the Central Pontide Mountains of Northern Anatolia are interpreted as being mantle and crust accretionary prisms which formed along the southern edge of the Laurasian Supercontinent prior to the closure of the Paleotethys Ocean and the Formation of Pangea together with the Gondwana Supercontinent. Elekdag is closely associated with the larger Cangaldag Island Arc and the larger Domuzdag HP mélange. During subduction in the Cretaceous the Elekdag Complex experienced up to eclogite-facies metamorphic conditions. Metamorphic rocks present in the study area include typical ophiolite assemblages with the addition of HP-LT blueschists, greenschist facies mineral assemblages, serpentinite, mica schists and HP-MT eclogites. The HP-LT units are contained within lenses along the boundary of the serpentinite body and are also in contact with the neighboring Domuzdag Complex. Typical mineral assemblages of the eclogites are garnet + omphacite + glaucophane + clinozoisite + white mica ± lawsonite ± tourmaline ± rutile. Blueschist mineral assemblages consist of garnet + glaucophane + clinozoisite + white mica + chlorite ± quartz ± lawsonite ± rutile. Most primary mineral assemblages have been heavily overprinted with lower grade hydrous mineral assemblages. Retrogression occurred due to lower pressures and temperatures during exhumation and the extensive infiltration of hydrothermal fluids within the rocks characterized by chlorite. Typical retrograde phases are glaucophane (for eclogites), as well as the common greenschist facies assemblage of chlorite + albite + clinozoisite ± stilpnomelane. The metabasite samples investigated show mid-ocean ridge basalt affinities (MORB) with at least one protolith being a cumulate. Constraints on maximum pressures and temperatures of metamorphism, and by extent depth of subduction and subsequent exhumation were inferred based upon geochemical and petrographic analysis. Two distinct samples were modeled in isochemical phase diagrams. One, a cumulate metabasite yielded maximum PT conditions of 21±2 kbar at 360 ± 50 °C based upon garnet and phengite compositional isopleths as well as a maximum temperature of metamorphism of 400 °C according to Fe/Mg cation exchange thermometry between garnet and clinopyroxene. A second modeled sample yielded lower pressure ranges of 10±2 kbar at a higher temperature of 500 °C which is in contrast to similarly thermometry results which give maximum temperatures of ~450 °C.
  • Öge
    Subduction Roll Back and the Generation of Wet and Decompression Melting
    (Eurasia Institute of Earth Sciences, 2019-05-03) Şen, Mehmet Barış ; Göğüş, Oğuz Hakan ; 602171007 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    Subduction zones are the major element of active tectonics (55.000 km) of planet Eart (Stern, 2002). Subduction zones are regions of the Earth affected by the sinking of relatively cold and dense oceanic lithospheres into the mantle. Geophysical and geological evidences have led to interpretation of oceanic lithosphere subduction beneath the Sunda and Japan subduction region. Active subduction is taking important role to creation of serial volcanic province. These volcanic areas show variable chemical properties such as alkaline and calc-alkaline compositions. Alkaline composition is related with low pressure conditions and common at ridge regions however they are observed at some subduction zones such as Sunda arc. Calc-alkaline magmatism is related with dehydration reactions at subduction slab. Volatiles inside the top of the subducted oceanic lithosphere are releasing at 80 - 200 km depth condition. Volatiles decrease the melting temperature and cause partial melt of mantle wedge (triangular asthenospheric window beneath the volcanic arc). Thickness of the subducting slab is changing with oceanic lithosphere age. Feature of the subduction is dominated by thickness of the slab which is changing with age. Numerous 2D numerical geodynamic experiments (I2ELVIS) in the context of the tectonic evolution of the region are conducted to test the effects of the oceanic lithosphere age on melt generation. Within the scope of the models, the age of the oceanic lithosphere has been tried by increasing the age from 50 million to 120 million years. The plate convergence rate was defined as 4 cm / year and 8 cm/yr. The model boundaries are 1400 km vertical and 4000 km horizontal. as defined. The geology of the layers used in the models is defined as follows; 10 km atmosphere, 2 km. ocean, 20 km. felsic upper continental crust (wet quartzite), 15 km. felsic lower crust (wet kurtzite), 3 km. upper oceanic crust (basalt), 5 km. lower oceanic crust (gabbro) and 2 km. width is used for the zone of weakness hydrated mantle. Model result for subduction are comparable with observations related to the geodynamic evolution of the Sunda. The mantle structure compared by seismic profiles, considering convergent rate of plate motion. Chemical composition distribution of volcanics are correlating with geochemistry studies.
  • Öge
    Eclogite İnduced Deformation of the Siberian Craton
    (Eurasia Institute of Earth Sciences, 2019-05-03) Ballı, Açelya ; Göğüş, Oğuz Hakan ; 602171001 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    The deformation of the cratons, whose roots are approximately 250 km deep is very difficult. The removal of the mantle lithosphere, which is one of the proposed mechanisms for the deformation of the craton that is stable for long periods, is carried out by many different processes. Deformation of the craton as a result of a gravitational instability is one of the most likely mechanisms. According to isopycnic hypothesis, lithospheric mantle of cratons thought to be buoyant due to their depleted composition, even though most of them Archean in age and cold. Since the mantle lithosphere of the craton is lighter in density than asthenosphere, an additional force is required for a gravitational instability to occur. This thermo - mechanical force causes deformation of the roots of the craton by creating an instability between the mantle lithosphere and the asthenosphere. The Siberian craton is one of the world's largest Archean - Proterozoic cratons. The Siberian craton has approximately 100 - 1300 m surface topography, 35 - 53 km MOHO thickness, and a maximum depth of 350 km LAB which are acquired from petrological studies, seismic tomography and gravity anomalies. Specifically, the LAB varies among 170-350 km and such depth change is not well understood. Until the formation of the Siberian craton is completed, it hosts many tectonic and magmatic events. These include active margin zones, continent collisions, and rift zones. As a result of pressure change in the active boundary regions, the transformation of basalt to eclogite takes place. Therefore, it creates a gravitational instability in the environment. Gravity anomalies observed near kimberlite fields, reflect the possibility of denser eclogitic bodies under the crust of Siberian craton. Our study focuses on testing potential deformation of the Siberian continental lithosphere with the presence of these eclogitic bodies. We performed 2D numerical experiments to investigate the effects of eclogite blocks that are varying in size and density. Crust rheology was prepared in accordance with Siberian craton. The density of the mantle lithosphere (3330 kg / m3 - 3410 kg / m3 +20 kg / m3) is changed to observe its effect on the system, and eclogite blocks of different size (5 km x 500 km, 10 km x 250 km, 25 km x 100 km) are added to the lower crust base to start a gravitational instability. According to model results, depending on the deformation of the mantle lithosphere, eclogite block can either stay attached to the lower crust, or it can be detached from it. In the case where the eclogite block attached to the lower crust, two different conditions: localized deformation (do not occur the drip mechanism) and non-localized deformation occurs due to the small-scale convection movement. Also, two different removal mechanism for the case where eclogite becomes detached are also observed: high degree deformation of mantle lithosphere, and the eclogite block pierce through the mantle lithosphere. Comparison of experimental results with geophysical data for MOHO and LAB depths showed that, the most convenient models for Siberian craton are the models where the dripping were not observed. Mantle lithosphere densities of 3350 kg / m3 or less yields the most consistent results. While the width of the eclogite block causes high-degree deformation, it is observed that with increasing thickness it leads to formation of viscous drips. Taking MOHO and LAB depths into account obtained from the model results, it has been observed that the model #A1, #A2 and #A3 agrees well with the BB' cross-section at 20.92 Ma, 25.36 Ma and 20.92 Ma, respectively. Experimental results indicate that, eclogite block(s) under the Siberian craton may still be there and craton itself does not undergo any significant deformation.
  • Öge
    Mobile Cratons, Subcretion Tectonics and Formation of Ttgs
    (Eurasia Institute of Earth Sciences, 2019-05-03) Çetiner, Uğurcan ; Göğüş, Oğuz Hakan ; 602171003 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    The formation of Archean cratonic lithosphere and TTG (Tonalite-Trondjemite-Granodiorite) suites is not well understood, in part because the style of global tectonics active at that time is uncertain. The non-plate tectonic hypothesis for formation and evolution of continents we test in this study involves: intense magmatism above mantle upwellings in an unstable single plate regime to form cratonic nucleii; imbrication and anatexis of crust-dominated oceanic lithosphere at convergent margins driven by mantle flow, with build-up and thickening of cratonic keels by collisions. We use 2D numerical geodynamic models to investigate whether differential motion between the convecting mantle and cratonic keels can induce horizontal motion of a craton to form an accretionary orogen. Using the convection code StagYY, we attempt to model a self-consistent subcretion of oceanic lithosphere pushed by a pre-imposed craton. Initially, 40 km thick basaltic crust, accompanied by 20 km thick sub-oceanic lithosphere, is introduced on both sides of the 230 km thick cratonic lithosphere, with an initial potential mantle temperature of 1750 K. The domain is divided by 64 vertical cells and 512 lateral cells corresponding to 660 km depth and 2000 km length. Both for upper and lower boundary, free-slip surface conditions are used. Left and right boundaries are periodic. Velocities are forced to be zero until a critical depth of 60 km, after that, a sub-lithospheric mantle flow of 4 cm/yr imposed into the model. Diffusion creep has chosen to be the main deformation mechanism for computational reasons. Our study involves investigating the effects of different parameters on the evolution of the experiments, such as; reference mantle viscosity, eclogite phase transition depth, yield stress of the oceanic lithopshere, and a change in the deformation mechanism. Our experimental results indicate that, cratonic keels can be mobilized by the sub-lithospheric mantle winds. We chose a reference model with typical yield stress (20 MPa), mantle viscosity (1020 Pa s), and eclogite transition depth (40 km) values, where craton becomes mobilized after ~160 Myr from model initiation, and oceanic lithosphere becomes subcreted at the cratonic margin. It has been found that, reference mantle viscosity has a significant impact on the exact time that the craton has become mobilized. Experiments with a 1021 Pa s reference mantle viscosity yielded in faster mobilizaiton times by a factor 22 – 23 times. In these models, subcretion of oceanic lithosphere at continental margins did not occur, but thickened oceanic lithosphere parts created downwellings resembling to subducting oceanic slabs. Lower mantle viscosities (1019 Pa s), however, could not generate sufficient stress to drift the craton away, but they led to a more vigorous convection and thermally eroded the cratonic roots. Increasing yield stresses from 20 MPa to 25 MPa and 30 MPa, made the oceanic lithosphere stronger and elongated the time needed for cratonic mobilization. Increasing it to 40 MPa led to a stable tectonic state, where craton did not become mobilized. Experiments with increased surface yield stresses did not provide an environment for subcretion tectonics, instead, lithospheric removal was due to eclogitic dripping where oceanic lithosphere became thick enough. Removal of the oceanic lithosphere changes velocity and orientation of the flows within the asthenosphere. In relation to that, evolution of some experiments contained convection cells generated within the mantle that ceased the motion of the craton, and even pushed it backwards for brief amount of time in some cases. Experiment performed to investigate the effect of deformation mechanism reflected the best example for this. In this case, rigthward moving craton traveled backwards at some point, created a subcretion on the left margin, and then, it started to move forward again to create a secondary subcretion, which has been classified as asynchronous double-sided subcretion. Our results indicate that, lithospheric removal mechanisms and craton mobilization times can vary with different parameters, but a displacement of 1350 km takes place in 30 to 40 Myr in all experiments, when the craton becomes mobile. Subcretion tectonics can only start in a narrow window, where surface yield stress is 20 MPa and reference mantle viscosity is 1020 Pa s, with the exception of eclogite transition depth being 60 km. Results indicate that subcretion mechanism can be achieved under given conditions, and TTG genesis via this mechanism can be valid when certain P-T conditions are met.
  • Öge
    Modeling the Structural Evolution of the Detachment Faults at Western Anatolia Back Arc System
    (Eurasia Institute of Earth Sciences, 2019-05-03) Bodur, Ömer ; Göğüş, Oğuz Hakan ; 602171002 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim Dalı
    Extensional tectonics in the western Anatolia-Aegean region feature exhumation of the metamorphic core complexes that is accommodated by low angle normal (detachment) fault systems. Specifically, the central Menderes massif contains two symmetrically developed outward facing (Gediz and Büyük Menderes) detachment faults, which accommodated large scale displacements. Additionally, there are many younger high-angle normal faults in conjunction with the initiation of extension and synextensional magmatism since the Early Miocene. The standard fault mechanical theory does not allow such orientations, the occurrence of these faults at low angle and the seismicity on them are still not well-understood. Here, we investigate the evolution of the normal fault systems on lithospheric scale using thermomechanical forward models. We employ the numerical finite element code ASPECT to compute the visco-plastic deformation within a model domain that is 500 km wide and 165 km deep. The initial condition of our model is designed to reproduce the first-order lithospheric structure at the onset of Western Anatolia extension approximately 20 million years ago and consists of an upper crust (25 km thick) with wet quartzite rheology, a lower crust (25 km thick) with wet anorthite rheology, and a mantle lithosphere (30 km thick) with dry olivine rheology. We conduct two model suits where we investigate the impact of key parameters within a plausible range: (1) we vary the extension velocities imposed on the margins of the model boundary from Vext = 1- 4 cm/year full rate. (2) we vary the friction strain weakening factor of the upper crust (fc = 0.1 to 0.5). Our models show that these two parameters directly control the initial dip angle and development of the normal faults. We find that major faults are formed initially at 50-52° dip but evolve towards shallower dipping angles, 10-15°, because of the isostatic adjustment due to thinning/exhumation of the crust. The sequentially tilted faults on where slip can no longer be accommodated are abandoned and left behind as inactive low angle fault surfaces. Basin ward migration of newer fault is formed in the hanging wall to accommodate strain. The tectonic evolution of the central Menderes region is best reproduced in our reference model with a friction strain weakening factor of 0.2 and an extension rate of Vext = 3 cm/yr. Namely, this model agrees well with the detachment faults shallowing dip angles, outward facing faults and symmetry with respect to the central Menderes massif. In addition, the exhumed massif has a dome shaped structure and the distance to one another (80 km) is comparable to those of Western Anatolia. Also, high angle normal faults are formed above the detachment faults, typical for Gediz and Büyük Menderes grabens. When the friction strain weakening factor of the upper crust and extension rates are changed, differences in these structural elements are observed. We conclude that our reference model supports the two rolling-hinge detachment system separated by elongated metamorphic domes with fold axes perpendicular to the direction of extension.
  • Öge
    Trakya Havzası Güneybatı Kesiminin Stratigrafisi Ve Geç Oligosen-erken Miyosen Deformasyonu
    (Avrasya Yerbilimleri Enstitüsü, 2019-11-15) Erbil, Ümitcan ; Okay, Aral ; 602171004 ; Katı Yer Bilimleri Anabilim Dalı ; Solid Earth Sciences
    Kuzeybatı Türkiye'de bulunan Trakya Havzası, Eosen-Oligosen yaşta çökel bir alanı temsil etmektedir. Havzada Orta-Geç Eosen döneminde başlayan sedimentasyon, Geç Oligosen döneminde sonlanmış, bölge yükselerek aşınmıştır. Bu yükselim ve aşınma döneminde Trakya Havzası'nda birçok kıvrım gelişmiştir. Bu yüksek lisans tezi çalışmasında, Trakya Havzası'nın güneybatı kesiminin Eosen-Oligosen stratigrafisi ve Geç Oligosen-Erken Miyosen deformasyonunun yapısal özellikleri incelenmiştir. Bu kapsamda araştırma yapmak üzere geniş bir antiklinal olan Korudağı bölgesi seçilmiş, klasik saha jeoloji yöntemi başta olmak üzere, LA-ICP-MS zirkon jeokronolojisi ve biyostratigrafi gibi yöntemler kullanılarak kaya stratigrafi birimlerinin yaşları tespit edilmiştir. Korudağı bölgesinin temel kayalarını Eosen öncesi yaşta metamorfik birimler oluşturur. Yunanistan'daki Rodop Çevresi Kuşağı'na dahil edilen metamorfik temel kayaları; fillat, sleyt ve rekristalize kireçtaşlarından meydana gelmektedir. Temel kayaları üzerinde uyumsuzlukla baskın olarak konglomeralardan ve eser miktarda kumtaşlarından oluşan Fıçıtepe Formasyonu bulunur. Fıçıtepe Formasyonu üzerinde sığ denizel platform karbonatlarından yapılı Orta-Üst Eosen yaşlı Soğucak Formasyonu yer almaktadır. Soğucak Formasyonu'nun üst kesiminden ölçülen bir adet kesit Korudağı bölgesindeki transgresyonun Geç Priyaboniyen (SBZ 20) döneminde gerçekleştiğini göstermiştir. Soğucak Formasyonu üzerinde uyumlu olarak, kalın bir yakınsak türbidit istifinden meydana gelen Keşan Formasyonu bulunmaktadır. Keşan Formasyonu içerisinden derlenen bir adet tüf örneğinden yapılan LA-ICP-MS zirkon yaşı Erken Oligosen (31.63±0.37 My) yaş vermiştir. Keşan Formasyonu içerisinde bu çalışma kapsamında üye mertebesinde tanımlanmış olan Çeltik Kireçtaşı bulunur. Baskın olarak pelajik kireçtaşları, az miktarda kalsitürbidit ve marnlardan oluşan Çeltik Kireçtaşı Üyesi'nin yaşı yapılan paleontolojik çalışmalar sonucu Üst Eosen (P15-P16/P17) olarak belirlenmiştir. Korudağı bölgesinde Orta-Üst Eosen döneminde başlayan çökelim dönemi Geç Oligosen-Erken Miyosen döneminde gerçekleşen kıvrımlanma ve yükselim sonucu bitmiş, Eosen-Oligosen birimleri uyumsuzlukla Neojen yaşlı karasal çökellerden yapılı Mahmutköy Neojen İstifi ve Mahmutköy Bazaltı tarafından örtülmüştür. Geniş bir antiklinali temsil eden Korudağı'nın oluştuğu döneme karşılık gelen bu deformasyonun yapısal özelliklerini belirlemek amacıyla bölgedeki tabaka duruşları incelenmiştir. Korudağı, yukarı doğru bakan, dik kıvrım eksenli, ekseni yatay dalımlı antiklinal bir yapıyı temsil etmektedir. Kıvrım ekseninin gidişi K65ºD yönlüdür. Korudağı antiklinalinin güney kanadı dikçe eğimlidir ve bir kör bindirme fayı sonucu gelişmiştir. Korudağı antiklinali yapı ve yaş bakımından Trakya Havzası'nın güney kesimindeki kıvrımlara benzerlik sunmaktadır. Bölgedeki kıvrım eksenlerinin gidişi, asimetrik kıvrım geometrileri ve bölgesel Neojen uyumsuzluğu, Korudağı antiklinali ve ilişkili kıvrımların, Geç Oligosen-Erken Miyosen döneminde tabakalanmaya paralel kısalma sonucu oluşmuş büklümlü kıvrımları temsil ettiğini göstermektedir.
  • Öge
    Sakarya Zonunun Orta Kesiminde Yer Alan Jura Öncesine Ait Temelin Özellikleri Ve Kökeninin Belirlenmesi
    (Avrasya Yerbilimleri Enstitüsü, 2020-04-15) Egi, Ali Yetkin ; Sunal, Gürsel ; 602161008 ; Katı Yer Bilimleri Anabilim Dalı ; Solid Earth Sciences
    Çalışma bölgesi Sakarya zonunun doğu kısmında ve Doğu Pontidlerin batısında yer almaktadır. Bölgenin jeolojisi özet olarak Jura yaşlı ve Neo-Tetis Okyanusu’nun güney pasif kıta kenarını oluşturan çökeller ve onun altındaki temel birimler olarak ifade edilebilir. Erken Jura transgresyonu Paleo-Tetis Okyanusu’nun kapandığı, Gondwana-Kıtası temel birimleri üzerinde gelişmiştir. Temel metamorfikler Tokat masifi fillat, şist, metabazit ve bunların içerisinde yer alan mermer mercekleri ile temsil edilmektedir. Yeşilırmak metamorfitlerinin içerisine faylı şekilde magmatik kütleler yerleşmiştir ve sonrasında da hep beraber bir metamorfizmaya uğramışlardır. Temeli temsil eden bu kayaçlar Alt Jura yaşlı karbonat ve kırıntılı birimlerince uyumsuzlukla örtülmektedir. Üst Kretase’de bölge derin denizel çökellerle temsil edilir. Paleosen dönemi çökelmenin görülmediği bir dönemdir. Lütesiyen ve Neojen birimleri daha yaşlı kayaları (Eosen karasal çökelleri, Kretase ve Jura denizel birimleri ve Jura öncesi temeli) uyumsuzlukla üzerlemektedir. Metamorfik istife stratigrafik ve paleontolojik verilere göre Pre-Silüryen-Silüryen (Alp, 1972) ve Triyas (Çapkınoğlu, 1998) yaşı verilmiş olsa da atfedilen bu yaşlar tartışmalıdır. Ayrıca birçok çalışmada bölgede iki ayrı temel tarif edilmiş ve bunlar arasında da farklı jeolojik ilişkiler belirtilmiştir. Bu çalışma ile bölgede jeolojik haritalama çalışmaları yapılarak temelde yer alan metamorfiklerin özellikleri ve bir birileri ile olan ilişkileri belirlenmiştir. Bu amaçla birimlerden yapısal ölçümler alınıp, petrografi çalışmaları ile birlikte kökenlerine dair veriler elde edilmiştir. Çalışma alanı içerisinde Jura öncesi temel Triyas yaşlı iki birimle temsil edilmektedir. Bunlardan ilki Triyas yaşlı gabrolarca kesilen (Eyüboğlu ve diğ., 2015) Yeşilırmak metamorfitleridir. Birim iyi yapraklanmalı ve yeşilşist fasiyesinde metamorfizmaya uğramış fillat-metabazitlerden oluşmaktadır. İkinci temel ise bu birimin üzerinde yer alan Karasenir formasyonudur. Bu birim çeşitli karbonat blokları içeren düşük metamorfizmalı (ankimetamorfik) bir istiftir. Her ne kadar bu birim Yeşilırmak metamorfitlerine bindiriyor olarak gösterilse de böyle bir ilişki arazide gözlenememiştir. Bu birim Yeşilırmak metamorfitleri üzerinde geçişli olarak gözlenmektedir. Triyas yaşında (erken?) olduğu düşünülen bu temel batı Sakarya temelinde yer alan Karakaya birliğinin eşleniği olarak atfedilmiştir.
  • Öge
    Upper Cretaceous Stratigraphy and Volcanism in İğneada Region, Pontides, NW Turkey
    (Avrasya Yer Bilimleri Enstitüsü, 2020-07-24) Sağlam, Ezgi ; Okay, Aral I. ; 602171006 ; Katı Yer Bilimleri ; Solid Earth Sciences
    The Pontide Upper Cretaceous magmatic arc can be traced for over 1000 km along the southern Black Sea coast from Georgia to Bulgaria. The arc extrusive sequence is wellexposed in İğneada region in Thrace close to the Bulgarian border. The Upper Cretaceous sequence in İğneada region overlies the schists and phyllites of Strandja Massif with an unconformity. The sequence consists at the base of Cenomanian shallow marine limestone, which pass up into carbonate-rich sandstone, marl and calcareous siltstone indicating deepening upwards. The sedimentary rocks pass up into a volcanic-volcaniclastic sequence of andesitic tuff, lapilli-tuff, lapillistone, agglomerate, andesitic and basaltic-andesitic lava flows. The volcanic-volcaniclastic sequence is divided into three domains for a detailed investigation and they are indicated on the prepared geological map as D1, D2 and D3. The volcaniclastic rocks are intercalated with lava flows, rare pelagic limestone and shale beds. The sequence starts with andesitic volcaniclastic rocks and lava flows, and changes to basaltic-andesitic and then, to andesitic and dacitic rocks. The calc-alkaline characteristic of volcanic rocks and negative Nb-Ta anomaly indicate a volcanic arc setting. Although it is disrupted by several normal faults, the volcanic sequence can be traced from older to younger along the coast of İğneada. The sea floor alteration, which is found in all volcaniclastic and volcanic rocks, the intercalated pelagic limestones, and turbiditic sedimentary structures show that the rocks were deposited in deep submarine conditions in an intra-arc to fore-arc environment.
  • Öge
    Antakya Ve Çevresindeki Aktif Fayların Araştırılması Ve Haritalanması
    (Avrasya Yer Bilimleri Enstitüsü, ) Lom, Nalan ; Tüysüz, Okan ; 277001 ; Katı Yer Bilimleri ; Solid Earth Sciences
    Bu çalışma kapsamında, jeolojik ve jeofizik yöntemler kullanılarak Antakya ve çevresinde etkili olan faylar ve geometrileri araştırılmış, bu fayların bölge morfolojisindeki etkileri incelenmiştir. Bu kapsamda öncelikle uydu görüntüleri ve sayısal arazi verileri kullanılarak morfolojik analizler yapılmış ardından saha çalışmalarında tektonik yapılar gözlemlenerek ölçümler alınmış ve haritalanmıştır. Belirlenen faylar yapısal jeoloji ve jeomorfoloji ağırlıklı, jeofizik destekli çalışmalar ile değerlendirilmiş ve aktiviteleri yorumlanmıştır. Çalışmada, Pliyo-Kuvaterner yaşlı çökeller, kırık sistemleri, depremlerle oluşan yüzey kırığı ile morfotektonik elemanlar detaylı olarak haritalanmıştır. Ayrıca, Antakya ve çevresindeki aktif fayların Yer Radarı (GPR) metodu kullanılarak incelenip bölgenin aktif tektoniğini araştırılmıştır. Jeolojik değerlendirmeler sonucunda graben içinde yanal atımlı ve düşey atımlı iki sistemin egemen olduğunu göstermiştir. Düşey atımlı faylar grabeni oluşturan faylar olarak nitelendirilirken Pliyosen ve Miyosen birimleri kesen yanal atımlı faylar aktif faylar olarak yorumlanmışlardır. Ancak kesin olarak bu faylanmaların ne zaman olduğuna dair veri elde edilememiştir. Yer Radarı ile toplamda 66 profil ölçüm alınmıştır. Aktif olduğu düşünülen Çöğürlü ve Sutaşı faylarının bölgedeki uzanımı incelenmiştir. Değerlendirmeler sonucunda basamaklı bir yapıda olan Sutaşı fayının GB'sına ait ölçümlerde fay izi tespit edilmiştir. Çöğürlü fayı üzerinde yapılan araştırmalar fayın Akdeniz kıyısına kadar uzandığı olasılıkla Kıbrıs Yayı ile bağlantılı olduğunu göstermektedir. Jeolojik ve jeofizik veriler Hatay Grabeni'nin DAFZ, ÖDFZ ve Kıbrıs Yayı etkisinde gelişen bir üçlü eklem olduğunu ortaya koymaktadır.