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ÖgeDetermination of pattern, timing and mechanism of the active tectonic deformation in the western flank of the Central Taurides(Graduate School, 2024-09-02)The Central Taurides is located in the southern margin of the Central Anatolian Plateau and corresponds to the upper crust of the subduction between African and Anatolian plates, with a high relief of up to 2 km. This mountainous region has distinctive geomorphological features and presents a unique setting to investigate the mechanism of orogenic plateau margin development related to subduction and topographic evolution around the Eastern Mediterranean. Here, we combine new kinematic data from exposed fault planes, tectonic landforms from high-resolution digital elevation models, microstructural analysis and U-Th and U-Pb geochronology on syn-tectonic calcites to elucidate the pattern, mechanism and timing of active tectonic deformation in the western Central Taurides, above the Cyprus Subduction Zone. Our geomorphic analyses reveal a post-orogenic transient actively deforming topography. The geomorphic markers constrain long-term surface uplift pattern with a mean cumulative surface uplift of 1,710 ± 50 m and shows an increasing trend from west to east, from 1,600 ± 50 to 1,800 ± 50 m. Our results suggest a dome-like uplift pattern in the west-east direction across the southern margin that reaches up to maximum cumulative uplift values in the quadrangle of Alanya-Başyayla-Ermenek-Gazipaşa. Our kinematic measurements on the exposed fault planes reveal the presence of normal, strike-slip, and thrust/reverse faults, indicating a multiphase history of brittle deformation. Microstructural studies on syn-tectonic calcites show brittle deformation features such as microcracks, brecciation, and calcite twinlets, providing evidence of tectonic control over calcite precipitation. U-Th ages of fault-related calcites show continuous normal faulting from the Middle/Late Pleistocene to the Holocene due to NE-SW horizontal extension, with a conspicuous clustering at circa 450 ka, indicating a connection/coupling between deep-seated and surface processes. It suggests that extensional deformation and rapid surface uplift may occur concurrently, creating relief-bounding normal fault zones and high-relief dynamic landscapes on a short timescale in the overriding plates. The U-Pb carbonate geochronology of syn-tectonic calcite samples indicates three distinct phases of faulting from the Late Cretaceous to the Quaternary. Thrust/reverse faulting events, which represents the first faulting phase, were observed in the Late Cretaceous. The second faulting phase, strike-slip faulting, occurred from the Early Eocene to the Early Miocene with a clear cluster in the Oligocene. Normal faulting was the last faulting phase and is prevalent from the Early Miocene to the Quaternary. The Late Cretaceous thrust/reverse faulting could be associated with the collision of different tectonic blocks in Anatolia. The Oligocene strike-slip shearing in the region was probably driven by the convergence and collision of tectonic plates in Eastern Anatolia and the resulting block rotations in Southern Türkiye. The onset of normal faulting in the Early Miocene indicates a shift towards extensional tectonics during the Oligocene-Miocene transition, which continuous until the present day. The last faulting phase has been possibly driven by the coupling geodynamic processes such as slab retreat, slab deformation and mantle upwelling associated with convergence along the Cyprus Subduction Zone. Our findings have significant implications for understanding the morphotectonic evolution and post-orogenic deformation in the plateau margins and geodynamic evolution of the Eastern Mediterranean.
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ÖgeBüyük orman yangını geçirmiş alanlarda yersel ölçüm ve serpinti radyonüklid yöntemleri (Berilyum-7 ve Sezyum-137) kullanılarak toprak erozyonu hızının belirlenmesi(Lisansüstü Eğitim Enstitüsü, 2023-12-27)Büyük orman yangınları yol açtığı büyük ekonomik kayıpların ve kimi zaman da neden olduğu can kayıplarının yanı sıra doğal ekosistem üzerinde de önemli değişikliklerin ortaya çıkmasına yol açar. Orman yangınlarının flora ve fauna popülasyonundaki değişimler, toprak ve ana kaya özelliklerinin değişmesi, yüzeysel akış ve erozyon miktarındaki artışlar, heyelan ve moloz akmalarının artışı gibi doğrudan alanda yol açtığı değişimler ilk akla gelenlerdir. Ancak bunlara ek olarak orman yangınının gerçekleştiği alanın kaynaklık ettiği çevre alanlarda da sedimantasyon miktarında artış, su kalitesinde azalma gibi önemli ekolojik sorunların da tetikleyicisi olduğu bir gerçektir. Ekstrem doğa olaylarının neden olduğu değişimlerin geçmiş jeolojik dönemlerde belirli periyotlarda gerçekleştiği ve doğanın bu tür değişimlerin etkilerine uyum sağlama eğiliminde olduğu bilimsel bir gerçeklik olsa da günümüzde meydana gelen doğal olayların hem ortaya çıkışında hem de etkileriyle mücadele edilmesinde insan etkisinin çok önemli bir paya sahip olduğu da yadsınamaz bir gerçekliktir. Bu bağlamda yoğun nüfus baskısıyla karşı karşıya kalan orman alanlarının çevresinde özellikle Akdeniz iklim bölgesinde küresel ısınmanın yol açtığı uzun ve daha kurak yaz döneminde gerçekleşen orman yangınları geniş alanları etkilemektedir. Gerek yangın sırasında yangın şiddetinin etkisiyle toprak özelliklerinin değişmesine bağlı olarak gerekse yangın sonrasında yangına maruz kalan arazideki hâlâ ekonomik değere sahip olan ağaçların kesilmesi, taşınması ve arazinin yeniden ağaçlandırılmasına yönelik ilgili merciler tarafından uygulanan ağaçlandırma ve diğer silvikültür çalışmaları sonucunda arazinin tekrar yangın öncesindeki şartlara ulaşması onlarca yılı alabilmektedir. Bu çalışmada Türkiye'nin güneybatı kıyısında Akdeniz iklimi etkisindeki Güneybatı Toroslar'da yer alan Göcek'in kuzeyinde 10 Temmuz 2019 tarihinde meydana gelen orman yangını ile Antalya İli, Kumluca ilçesi, Adrasan kuzeyinde 24-29 Haziran 2016'da toplam 15 km2 ormanlık alanda etkili olan orman yangınından sonra arazide meydana gelen değişimlerin erozyon hızına etkileri Türkiye'de ilk defa serpinti radyonüklidleri yönteminden yararlanılarak tespit edilmiştir. Çalışmada bu yöntemin dışında yangın alanındaki jeomorfik özellikler ile yangın şiddeti arasındaki ilişkileri ortaya koymak amacıyla İHA (İnsansız Hava Aracı) kullanılmıştır. Ayrıca doğrudan arazi ölçümlerine dayalı olarak yersel ölçüm yöntemleri kullanılmıştır. Bunlara ek olarak, kullanılan farklı yöntemler arasındaki validasyonun da sağlanması açısından yersel LİDAR ölçümünden de yararlanılarak yüksek çözünürlüğe sahip nokta bulutlarından elde edilen verilerle de diğer yöntemlerden elde edilen sonuçların desteklenmesi amaçlanmıştır. Ayrıca ülkemizde yürürlükte olan mevzuatlar gereği orman yangınları sonrasında yanan arazilerin kısa sürede yanmış ağaçlardan temizlenmesini kapsayan boşaltma kesimi (ing. salvage logging) yoluyla arazinin doğal yapısının büyük ölçüde zarar görmesinin yol açtığı antropojenik tahribatın bitki örtüsünün yenilenme hızı üzerindeki etkisi, Antalya ili Alanya ilçesi Sapadere mevkiinde 30 Haziran-2 Temmuz 2017 tarihleri arasında yangına maruz kalan 20.7 km2'lik alana ait Spot uydu görüntüleri kullanılarak NDVI analizi ile ortaya koyulmuştur. Çalışmada serpinti radyonüklidleri yönteminin, sarp arazi koşullarında örnek alınmasının zorluğu dışında orman yangını geçirmiş arazilerde erozyon hızının tespiti açısından elverişli sonuçlar verdiği görülmüştür. Son yıllarda kullanımı ve teknolojisi hızlı bir şekilde artan İHA tabanlı ölçüm ve analiz teknolojilerinin erişilmesi güç alanlarda ve özellikle de dönemsel değişimlerin incelendiği çalışmalarda başarılı sonuçlara ulaşılmasını sağladığı görülmüştür. Yersel ölçüm yöntemlerinden istenilen sonucun alınabilmesinin ise kurulan düzeneklerin dış etkilerden azami ölçüde korunabilmesine bağlı olduğu ve ülkemizde orman yangını sonrasında uygulanan restorasyon çalışmalarında başvurulan yöntemler göz önüne alındığında yersel ölçüm yöntemlerinden sonuç almanın ülkemiz şartlarında oldukça zor olduğu tecrübe edilmiştir. Çalışma sonucunda, 2 yıl boyunca gerçekleştirilen arazi çalışmaları ve kullanılan metodlar ile gelecekte daha pratik ve hızlı sonuç verebilecek bir yöntem olarak serpinti radyonüklidlerinin orman yangını geçirmiş arazilerde meydana gelen erozyonun ölçülmesinde etkili bir yöntem olduğu ortaya koyulmuştur. Ayrıca İstanbul Teknik Üniversitesi Bilimsel Araştırma Projeleri Birimi'nin (Proje No: 41755) ve TÜBİTAK-2232 Uluslararası Lider Araştırmacılar Programı (Proje No: 118C329) desteği ile geliştirilen bu çalışma, ülkemizde henüz yaygınlaşmamış olan orman yangını geçirmiş arazilerde serpinti radyonüklidleri ile erozyon hızının tespit edilmesine yönelik çalışmalar için öncülük etmesinin yanı sıra çok yüksek çözünürlüklü topoğrafik modelleme ile alansal, hacimsel hesaplama çalışmalarının da entegre edilmesiyle bu alandaki çalışmalara ivme kazandırılabilecek ve farklı disiplinlerden araştırmacıları da bir araya getirebilecek bir çalışma olmuştur. Gerçekleştirilen çalışma ile orman yangını geçirmiş arazilerde meydana gelebilecek; erozyon, birikim, moloz akmaları ve heyelan gibi zamansal değişimlerin bölgesel etkilerinin incelenebileceği ve bu tür olayların yol açabileceği tehlikelerin öngörülebileceği ortaya koyulmuştur. Çalışmada özellikle yangın sonrasında yapılan boşaltma kesimleri ve takip eden iyileştirme çalışmalarının yangın sonrası gelişebilecek moloz akma tehlikesini neredeyse beş katı bir hızda artırdığı ve bitki örtüsünün doğal yenilenme süresini de olumsuz etkilediği sonucuna ulaşılmıştır.
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ÖgeBadland systems in Turkey: A holistic approach to understand the formation, controlling factors and geomorphologic characteristics(Graduate School, 2023-10-19)Badlands are extremely rugged, outstanding landscapes that can be seen in all ice-free climate regions over erosion-susceptible unconsolidated materials, and they have drawn attention with their spectacular and iconic. The distribution of badlands is primarily influenced by the occurrence of loose and unconsolidated rocks (such as marl, sandstone, mudstone, etc.). These lithological units, in conjunction with various environmental elements such as climate, tectonics, vegetation, and topography, collectively shape the appearance and dynamics of badland landscapes. Since badlands have the largest sediment flux and erosion rates, they are considered to be erosional hot spots. However, the morphological characteristics, origins, regional characteristics, and development processes of these badlands are not well known. Unlike nearly all badland studies conducted at the experimental site and watershed scale, the broader-scale evaluation has been neglected in the analysis of badland distribution, characteristics, and dynamics. The first part of the thesis provides an integrative new insight into badland landscapes by investigating the distribution, characteristics, and controlling factors of Turkish badlands on a broad, regional scale. Turkish badlands were inventoried using aerial imagery and studied their distribution using K-means clustering, an unsupervised machine learning algorithm, based on a set of major conditional geo-environmental factors that control the regional distribution and characteristics of badlands, including tectonics, lithology, topography, climate, and vegetation. Here, a total of 4494 km2 of badland areas were identified which are non-uniformly distributed across Turkey, substantially clustered in the Central Anatolian Plateau (CAP). According to regional analyses, a total of five badland regions have been determined comprising three major types classified as Semi-arid, Mediterranean, and Montane (humid), together with two transitional types in-between the Semi-arid and Montane badland regions. The results indicate that temperature seasonality, mean annual precipitation, and precipitation seasonality are predominantly assigned to the badlands clusters. The clastic rocks are revealed as the most crucial and inevitable factor for the development of Turkish badlands, which are represented in a wide geologic time-scale (Cretaceous to Quaternary) and diverse lithological units (i.e., lacustrine, volcaniclastics, and terrestrial). Neogene and Paleogene terrestrial clastics (77 %) constitute the majority of the lithologic settings of these badland landscapes. The active and complex tectonic history of Turkey has portrayed the fundamental frame of the identified badland regions, by providing a susceptible environment (i.e., development of sedimentary basins) and promoting badland development through successive base-level changes. Furthermore, tectonically-modulated (i.e., formation of orogenic belts, and uplifting of CAP) climate dynamics outline the distribution pattern and differentiation of the regional characteristics of badlands in Turkey. Overall, the regional-scale approach to badland mapping and regional synthesis may decipher not only the tectonic and climatic conditions of the identified badlands regions but may also contribute to the implementation of future effective strategies for the detection and mapping of erosion-susceptible and high sediment flux areas in very broad spatial contexts of similar unexplored territories. An ever-present intricate association between weathering and erosional processes is largely controlled by climate disparities. Weathering as a predisposing process for natural hazards, landform evolution, and sediment mobility hosts key uncertainties in our understanding of how climate controls differential weathering types and rates. Here, the second part of thesis shows an approach to test the hypothesis controlling of weathering trends with the influence of seasonal characteristics of precipitation and temperature, which has been not well understood in badland landscapes, yet. Previous studies have adopted a rainfall simulation approach either in the field or laboratory, which is essential but is also limiting in that only steady climate conditions can be monitored in understanding weathering dynamics. In this context, by taking advantage of the laboratory environment to accomplish the aim of this part, the climate settings were simulated by exposing samples collected from four different climates and sedimentary environments previously defined as characteristic badland landscapes in Turkey to the seasonal precipitation and temperature conditions in twelve sequential seasons mirroring 3-years in order to understand the weathering rebounds. The pH, electrical conductivity (EC), ion, and surficial changes have been used as chemical and physical proxies, respectively, in referring to certain types and trends of weathering. Based on the incontrovertible influence of sediment physicochemical properties (especially high SAR values) on weathering processes, the findings reveal that sinusoidal trends attaining their peak level in spring in Na+, which overcomes other ions, contribute to an accelerated dispersion degree with concurrently decreasing pH in marly sediments in the arid region. Additionally, the recurrent increase pattern of Ca2+, particularly in winter seasons, can enhance the extent of sediment aggregations in Mediterranean sandy mudstones. In conclusion, consistent with previous studies, wetting–drying cycles are crucial in physical weathering and regolith behavior, which resulted in cyclic deep crust formations in the spring and summer seasons due to the higher swelling capacity of samples. Overall, this study demonstrates how seasonal changes in climate regulate the degree of chemical and physical weathering processes in badland landscapes. The combination of bedrock weathering, climate seasonality, and the controversial contributions of hillslope and river erosion processes, as part of the earth's dynamic systems, is what primarily develop badland environments. Although modern definitions make it clear that gully channels dominated by overland flow, mass movements dominated by gravitational processes, and piping driven by subsurface processes are all necessary for badland initiation, the questions remain to be tackled regarding their topographic position in the landscape. The third and last part of thesis focused on this problem by comparing Turkish badlands and globally known badland sites in order to understand the geomorphometric and topographic imprints of badlands. As a result, the topographic character of badlands at the sub-catchment scale may provide an adequate example of a transitional domain from a diffusive erosional process to a fluvial erosion process.
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ÖgePaleoclimatology and glacial geochronology of the Western Taurus (Sw Türkiye) using comparative, relative and numerical methods(Graduate School, 2024-07-26)Türkiye possesses a remarkable heritage of the Late Pleistocene glaciations, evident across almost all of its lofty mountainous. Numerous individual mountains, particularly in the Eastern Black Sea and Taurus mountain ranges, host most of these glacial landscapes. In the 20th century, many pioneering studies on Late Pleistocene glaciations were conducted by various researchers in Anatolia. However, it was not until the 21st century that a comprehensive understanding of the glaciers in both spatial and temporal dimensions became possible. Thanks to numerical dating techniques, we now know the temporal resolution of the glaciation. Among these methods, the Terrestrial Cosmogenic Nuclide Dating (TCND) has gained considerable popularity since the early 2000s. In this study, first I reviewed the existing records on glacial chronology in the SW Türkiye. Additionally, I employed TCND to elucidate and fill certain gaps in the glacial geochronology of the Western Taurus Mountains. Finally, I tested a calibrated dating technique known as Schmidt Hammer Exposure-Age Dating (SHD) on different lithologies in the region for a cross-validation of TCND ages. In the first part of this thesis, the Late-glacial to Holocene glacier chronologies in Türkiye are reviewed. Despite the extensive extent of Turkish glaciers during the Last Glacial Maximum (LGM), traces of glaciers from the Late-glacial period are notably scarce in Türkiye. Certain landforms have been evaluated as Late-glacial and/or younger, but solid evidence, such as numerical dating, has not been obtained. In this section, Late-glacial and Holocene glacial areas are identified based on their TCND chronologies. Most of these areas are part of the Taurus Mountains, including the Dedegöl Mountains, Geyikdağ, Bolkar Mountains, and Aladağlar. Younger Dryas advances are evident in these mountains, especially in Aladağlar. Erciyes Volcano is the only location outside the Taurus Mountains in this study. Generally, the Late-glacial to Holocene glaciers of Turkish mountains extend from 14.8 ± 2.9 ka to 1.0 ± 0.3 ka, with certain Early to Late Holocene ages. Evidence for Little Ice Age (LIA) glacier advances is rare in Türkiye. Despite the rich glacial chronology of the Taurus Mountains, there are still areas with well-developed glacial geomorphology but lacking a strong dating control. In this thesis, I examined two of these areas to reveal their glacial history. One of these areas is known as Mount Barla, situated in the northernmost part of the Western Taurus Mountains. Polygenetic and polycyclic processes play an important role in the origin of the glacial valleys of Mt. Barla. Glacial, karst, mass movement, and fluvial processes are intertwined, paving the way for glacial valley formations. The paleoglaciers here date back to 78.5 ± 17.6 ka (MIS5). It is also observed that there was a co-deglaciation between two different glacial valleys. The TCND ages indicate that these glacial retreats occurred around 42.1 ± 5.2 ka and 45.5 ± 6.8 ka (MIS 3). Despite the absence of an LGM deglaciation, the final glacial retreat dates back to 16.6 ± 2.6 ka (Late-glacial). Mount Davraz is another mountain with a well-established glacial geomorphology. However, this mountain has also lacked numerical ages until this thesis. It is located roughly 30 km south of Mount Barla, yet the paleoglaciers shaped this mountain's geomorphology in a notably different manner. The peculiar glacial geomorphology, considering its relatively small scale, is attributed to the existence of piedmont glaciers during the Late Pleistocene. The paleoglaciers within the cirques on the north-facing slopes, aligned in an E-W direction, were sufficient to support these piedmont glaciers. The paleoglaciers of Mount Davraz most probably benefited from strong southerly winds. These winds carried snow from the relatively flat top side to the north-facing slopes of the mountain. Consequently, the piedmont glaciers moved northward, extending over a northerly flat area and forming the Davraz paleoglacier. In this study, the remnants of this paleoglacier were dated using the TCND method. These remnants, known as "hummocky moraines," are common landforms formed after the disappearance of an ice sheet or a piedmont glacier. I utilized TCNs obtained from glacial boulders located on these moraines to calculate the latest deglaciation phase in Mount Davraz. The results indicate two periods: the Davraz paleoglacier began to retreat from east to west around 21.8 ± 2.4 ka (LGM) and completely disappeared around 17.7 ± 2.2 ka (Late-glacial). Finally, I utilized Schmidt Hammer Exposure-Age Dating (SHD) to evaluate its applicability on Mount Sandıras, Karadağ, and Akdağ, as part of the Western Taurus Mountains. I measured rebound values (R-values) from the glacial surfaces to assess surface hardness. These measurements were conducted on both dated ("control surfaces" with TCND ages) and undated surfaces (test surfaces), with each control and test surface forming a sample group. The primary objective of this approach was to ascertain whether serpentinized harzburgite (Mount Sandıras) and limestone (Karadağ and Akdağ) surfaces are suitable for SHD applications. While the method yielded partial success with Mount Sandıras samples, the results from Karadağ and Akdağ did not align with expectations. The SHD glacial chronology of Mount Sandıras exhibited a substantial fit with its TCND glacial chronology.
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ÖgeDifferential tectonics of Aydın Range in western Anatolia Extensional Province: Inferences from catchment-wide erosion, river incision, and range-front deposition(Graduate School, 2023-10-27)The western Anatolian Extensional Province is a rapidly extending region characterized by dynamic landscapes resulting from the ongoing deformation of the Earth's crust. The Aydın Range, located along the northern margin of the Büyük Menderes Graben, is a major horst within the western Anatolian Extensional Province. This region has experienced a series of extensional events since the Late Oligocene, leading to ongoing uplift and erosion, shaping a complex landscape of mountains, valleys, and river systems. The tectonic deformation within the Aydın Range has not been uniform, resulting in differential uplift along the range and variations in erosion rates. This differential uplift has shaped the landscape, giving rise to distinctive erosional and depositional landforms along the northern margin of the Büyük Menderes Graben. The morphostratigraphy and morphology of these landforms provide valuable insights into the source-to-sink relationships and the Quaternary tectonics of the region. The active tectonic regime and steep topography of the Aydın Range create favorable conditions for enhanced erosion rates, leading to the development of the distinctive range-front deposition. However, the understanding of the active tectonics of the Aydın Range and its relationship to catchment erosion, river incision, and range-front deposition remains limited. To understand the differential tectonic uplift pattern of the Aydın Range, this thesis focuses on erosional and depositional features along the southern flank of the Aydın Range. The main objective of this Ph.D. thesis is to unravel the interplay between differential rock uplift dynamics of the Aydın Range and the range-front depositional and erosional patterns within the range, considering the tectonic activity, lithology, and varying erosion rates across the region. The study area offers favorable conditions for analysis, including numerous alluvial fans aligned along a segmented normal fault, similar climatic and vegetative characteristics within catchments, and a mixture of granite and gneiss lithologies. A comprehensive approach combining catchment-wide erosion analysis, river incision analysis, river longitudinal profile analysis, and range-front deposition analysis is employed. Catchment-wide erosion patterns, based on 10Be cosmogenic nuclides are examined to understand the relative contributions of various factors on erosional dynamics and decipher the tectonic uplift pattern of the range. River incision processes and channel characteristics are investigated to gain insights into underlying tectonic processes and their spatial variations. Furthermore, the morphology of alluvial fans at the range front are studied to evaluate tectonic uplift and the relative contributions of different processes to sedimentation patterns. Higher catchment-wide erosion rates and higher river incision rates in Section 3 and Section 5 of the Aydın Range are shown by the results. In addition, higher channel steepness index values and slope break knickpoint distributions imply that a higher rock uplift rate is responsible for thicker alluvial fans in sections 3 and 5. In contrast, Section 1, section 2, and Section 4 have lower catchment-wide erosion rates and lower river incision rates. In addition, the lower ksn and absence of slope break knickpoints in these sections is an indication that these sections have lower tectonic rock uplift. This resulted in the less thick and spatially larger distribution of alluvial fans in Section 1, section 2, and Section 5. A comprehensive understanding of the differential tectonics and range-front deposition processes is provided by the source-to-sink approach employed in this thesis, enhancing knowledge of the active tectonics and surface processes in the region. Additionally, the detailed morphostratigraphy of Quaternary landforms in the study area provides valuable insights into landscape evolution and hazard assessment in this dynamic setting. The map of Quaternary landforms fills the existing gaps in the region-wide correlations and maps associated with the Quaternary geology and geomorphology, facilitating a more comprehensive understanding of the tectonic processes shaping the Aydın Range.