Plio-quaternary evolution of the Kucuk Menderes Graben southwestern Anatolia, Turkey

The Kucuk Menderes Graben (KMG) is part of the horst-graben system of southwestern Anatolia (Turkey), bounded by the Bozdag horst in the north and the Aydin horst in the south. The Plio-Quatemary evolution of the KMG has been evaluated using the nature of the Miocene-Quaternary fill sediments and palaeostress analysis of slip data measured in different parts of the graben

Süphan stratovolkanı'nın volkanostratigrafisi ve jeokimyasal evrimi

TÜBİTAK MAG01.09.2009Doğu Anadolu Bölgesinde yer alan çarpışma kökenli volkanizma kuzeydoğuda Erzurum-Kars Platosundan güneyde Karacadağ’a kadar uzanan geniş bir alanda yüzeylenmektedir. Bölgenin yaklaşık olarak 2/3 sini kaplayan volkanizma irili ufaklı çıkış merkezleri ile büyük hacimlere sahip kalkan ve stratovolkanlar ile karakterize edilir. Van Gölü’nün kuzeyinde yer alan Süphan Stratovolkanı 4050 m yüksekliği ile Doğu Anadolu’da yer alan Kuvaterner yaşlı volkanların en önemli üyelerinden biridir. Neojen-Kuvaterner yaşlı sedimanter birimler üzerine yerleşen Süphan volkanizmasının ilk ürünleri debris avalanche, I. evre piroklastik ürünler ve riyolitik obsidiyen lavlarıdır. Bu birimlerin üzerine ise bazalttan riyolite kadar uzanan lav akışları, riyolitik/dasitik domlar, piroklastik birimler gelmektedir. Volkanizmanın en son ürünleri ise Aygır Maarı’na ait piroklastik birimlerdir. Mineralojik-Petrografik çalışmalar ve lavların major-iz element karakteristikleri volkanizmanın gelişiminde plajiyoklaz + olivin + klinopiroksen + ortopiroksen + amfibol + biyotit + K-felsdpat fraksiyonel kristalleşmesinin etkin olduğunu göstermektedir. Süphan volkanikleri genel olarak subalkali ve alkali karakterler arasında geçiş göstermektedir. İz element içerikleri ele alındığında HFS elemetler LIL elementlere oranla, LRE elementler HRE elementlere oranla zenginleşme göstermiştir. Volkanikler içerisinde yeralan anklavların jeokimyasal özellikleri Süphan volkanizmasının genel karakteri ile uyum göstermektedir. Th/Y-Nb/Y ve izotop korelasyon diyagramları (87Sr/86Sr -143Nd/144Nd, 87Sr/86Sr – Pb206/Pb204, Pb207/204-Pb206/204) volkanizmanın kaynağının dalma-batma bileşeni ile zenginleşmiş bir manto kaynağı olduğunu işaret etmektedir. Bununla birlikte Ba/Nb - Ce/ Nb diyagramı üzerindeki karışım eğrisi de Süphan volkaniklerinin zenginleşmiş bir manto kaynağı ile dalma-batma bileşeni içeren bir kaynağın karışımından oluştuğunu göstermektedir. Doğu Anadolu Bölgesi’nde kabuk kalınlığı ile ilgili jeofizik tabanlı çalışmalar da göz önüne alındığında bu manto kaynağının, dalan levhanın krılması (slab breakoff) yoluyla yitim bileşeni kazanmış astenosferik bir kaynak olabileceği öngörülmüştür. Volkanikler üzerinde gerçekleştirilen Ar-Ar yaş analizleri trakitik lavlar için 0.55±0.34 ile 0.037±0.020 my arasında riyolitik lavlar için ise 0.040±0.022 my yaş vermiştir.Collision-related volcanics in Eastern Anatolia are exposed in a broad zone from the Erzurum-Kars Plateau in the northeast to Karacadağ in the south. Volcanic rocks covered two thirds of the plateau and are characterized by secondary eruption centers and huge shield and stratovolcanoes. Süphan Stratovolcano, located to the north of the Lake Van is one of the most important Quaternary volcanos in Eastern Anatolia with its 4050 m high elevation. Initial products of the Süphan stratovolcano which overly the Neogene-Quaternary sedimentary rocks are the debris avalanche, Ist cycle pyroclastic rocks and rhyolitic obsidian flows. These units are overlain by lava flows with compositions ranging from basalt to rhyolite, rhyolit-dasidic domes and pyroclastic rocks. Aygır maar deposits are the last products of the volcano. Mineralogical-petrographical and major-trace element compositions of the volcanic products point to the effects of plagioclase + olivine + clinopyroxene + ortopyroxene + amphibole + biotite + K-feldspar fractionation in the evolution of the volcanics. Süphan volcanics are transitional between subalkaline and alkaline character. LIL and LRE elements are enriched over HFS and HRE elements respectively. Most of the Süphan enclaves show similar geochemical properties with the Süphan volcanics. Th/Y-Nb/Y and isotope correlation (87Sr/86Sr -143Nd/144Nd, 87Sr/86Sr – Pb206/Pb204, Pb207/204-Pb206/204) diagrams point out a subduction modified enriched mantle source for the source of the volcanics. Mixing curves on Ba/Nb - Ce/ Nb diagrams further suggest that the Süphan volcanics are formed by mixing of an enriched mantle and a source bearing effects of subduction. In the light of geochemical constraints and recent geophysical data regarding lithospheric structure of eastern Anatolia, the source of the Suphan volcanics is interpreted as an astenospheric mantle bearing the effects of previous subduction events via slab breakoff. Ar-Ar ages of the trachytes and rhyolites range between 55±0.34 - 0.037±0.020, 0.040±0.022 ma respectively

Strength of selection pressure is an important parameter contributing to the complexity of antibiotic resistance evolution

Revealing the genetic changes responsible for antibiotic resistance can be critical for developing novel antibiotic therapies. However, systematic studies correlating genotype to phenotype in the context of antibiotic resistance have been missing. In order to fill in this gap, we evolved 88 isogenic Escherichia coli populations against 22 antibiotics for 3 weeks. For every drug, two populations were evolved under strong selection and two populations were evolved under mild selection. By quantifying evolved populations' resistances against all 22 drugs, we constructed two separate cross-resistance networks for strongly and mildly selected populations. Subsequently, we sequenced representative colonies isolated from evolved populations for revealing the genetic basis for novel phenotypes. Bacterial populations that evolved resistance against antibiotics under strong selection acquired high levels of cross-resistance against several antibiotics, whereas other bacterial populations evolved under milder selection acquired relatively weaker cross-resistance. In addition, we found that strongly selected strains against aminoglycosides became more susceptible to five other drug classes compared with their wild-type ancestor as a result of a point mutation on TrkH, an ion transporter protein. Our findings suggest that selection strength is an important parameter contributing to the complexity of antibiotic resistance problem and use of high doses of antibiotics to clear infections has the potential to promote increase of cross-resistance in clinics

Tectonic and stratigraphic characteristics of the Koyulhisar segment of the North Anatolian fault zone (Sivas-Turkey)

Ph.D. - Doctoral Progra

Determination of Stress Orientation Using Slip Lineation Data in Pliocene Around Derinkuyu Fault Nevşehir

Slip lineation data developed on the cooling joints of a Pliocene ignirnbrite sheet are measuremed in the vicinity kuyu Fault to determine the state and the orientation of stresses in the region. The data are taken along three different survey lines in order to improve the reliability of the data as well as to observe the change in the nature of reactivation as a of distance to the main fault. The analysis involved in the evaluation of the data to find the stress are graphical solutions, namely, the and P-T dihedra methods. The solutions of the methods have shown that a, is sub-vertical. and and are sub-horizontal There is no preferred orientation of reactivation as displayed by the development of slickensided surfaces in all directions. terns of the diagrams are consistent in all survey lines indicating that the distance to the main fault is not significant. there is not any direct control of the main fault on the development of the reactivation of preexisting cooling joints, but rather the fault is a result of the present state of stress which reflects a typical example of radial stress field

Filtering of satellite images in geological lineament analyses: an application to a fault zone in Central Turkey

Lineament extraction and analysis is one of the routines in mapping large areas using remotely-sensed data, most of which is the satellite images. In this study, we aimed to test different lineament extraction techniques including single band, multiband enhancements and spatial domain filtering techniques. A fast algorithm has been developed for time and cost limited surveys in an area with known dominant and/or any selected orientation of lineaments. During the study for single band analysis, histogram equalization and stretching, for multiband, Principal Components Analysis (PCA) and for spatial domain filtering Prewitt and Sobel filters are utilized. Furthermore, we have developed a new algorithm which consists of a combination of large smoothing filters and gradient filters, in order to get rid of the artificial lineaments which are out of interest and to determine discontinuous and/or closely spaced regional lineaments. The results are as follows; the number of lineaments and their total lengths are 218 285.3 km using the single band; 255 343.9 km in multiband enhancements, and 347 644.9 km in the combination of spatial domain filtering including our algorithm. The 59.17 per cent increase in the number of lineaments and the 126.04 per cent increase in the total lengths indicate that a combination of spatial domain filters is the most cost-time efficient algorithm in lineament analyses