AYBE- Katı Yer Bilimleri Lisansüstü Programı - Yüksek Lisans

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http://hdl.handle.net/11527/268

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Konu "Coğrafya" ile AYBE- Katı Yer Bilimleri Lisansüstü Programı - Yüksek Lisans'a göz atma
  • 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
    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
    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.