Destekleme ve Yetiştirme Kurslarına (DYK) İlişkin Ortaokul Öğrencilerinin Görüşleri

DergiPark: 566362tredBu araştırmanın amacı ortaokul öğrencilerinin MilliEğitim Bakanlığı'na bağlı destekleme ve yetiştirme kursları (DYK) hakkındakigörüşlerini belirlemektir. Tarama yönteminin kullanıldığı araştırmanınörneklemini taşımalı eğitim veren bir ortaokulda kurslara devam eden 118ortaokul öğrencisi oluşturmaktadır. Araştırmacılar tarafından geliştirilen vedokuz açık uçlu sorudan oluşan yazılı görüş formu kullanılarak toplananverilerin çözümlenmesinde betimsel analiz yaklaşımı kullanılmıştır. Çalışmanınsonucunda, öğrencilerin yarısından fazlasının ders seçiminde kendi iradesinikullanırken kalanların ailelerinin ve okul yönetiminin yönlendirmesi ileseçtikleri belirlenmiştir. Bulgular DYK’ların genellikle test çözme ve konutekrarı yapma seklinde yürütüldüğünü göstermektedir. Kurslarda en yaygınkullanılan ders materyallerinin akıllı tahta, soru bankaları ve ders kitaplarıolduğu belirlenmiştir. Bununla birlikte öğrenciler akıllı tahtalarınetkinliğinin arttırılabilmesi için tablet olması gerektiğine vurgu yapmışlardır.Okul yönetiminin kurslar konusunda oldukça ilgili olduğunu belirten öğrencilerkursların gün sonunda olmasından dolayı çok yorulduklarını ifade etmişlerdir.Ayrıca yardımcı kitap eksikliği öğrenciler tarafından ifade edilen kurslarailişkin bir diğer sorundur. Bunun yanı sıra bazı öğrenciler kurslardasıkıldıklarını ve daha eğlenceli geçmesini istediklerini belirtmişlerdir

Tectonics Of The Northwest Anatolia And Palaeomagnetic Results

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1995Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 1995Batı Anadolu'nun tektonik evrimine ışık tutmak amacıyla; Çanakkale- Foça arasında kalan ve doğuda Bergama hizasından sınırlanan çalışma alanından 8 üst Oligosen, 35 alt-orta Miyosen ve 4 üst Miyosen olmak üzere 47 paleomanyetik mevkiden numune toplanmış ve bu mevkilerden sadece ikisi duraylı sonuç vermediği için değerlendirme dışı tutulmuştur. Numune toplama, mıknatıslanma doğrultularının ölçülmesi ve ikincil mıknatıslanmaların temizlenmesinde paleomanyetik teknikler kullanılmıştır. Paleomanyetik verilerin değerlendirilmesinden çıkan sonuçlar şunlardır: 1-) Üst Oligosen yaşlı mevkiler saatin ters yönünde 20°-30° arasında bir dönmenin olduğunu göstermektedir. 2-) Çalışma alanında en yaygın olarak bulunan alt-orta Miyosen yaşlı volkanizmaya sahip mevkilerde; Edremit Körfezi'nin kuzeyi için saatin ters yönünde 25°'lik bir dönme, güneyi için ise yine saatin tersi yönünde 15°-40° arasında dönmelerin olduğu tespit edilmiştir. Yine aynı yaşlı kayaçlarda; Assos ve civarında, listrik faylanmadan ötürü oluşan bir çok mikrobloğun farklı doğrultu ve eğime sahip olacak şekilde düşerek yerdeğiştirdikleri saptanmıştır. Edremit Körfezi'nin güneyinde ise Kozak Dağı diğer mevkilere göre ters yönde (saat yönünde 31°) bir dönme gösterdiği için bir blok olarak ayırtlanmıştır. 3-) Üst Miyosen yaşlı mevkilerin ise, saatin tersi yönünde 16°'lik bir dönmeye sahip olduğu bulunmuştur. Bu verilerin ışığı altında; kuzeybatı Anadolu'nun Neojen'den bu yana saatin tersi yönünde bir dönme hareketi geçirdiği ve bu dönme esnasında, Edremit Körfezi'nin kuzey ve güney kesimindeki levhaların birbirlerine göre farklı hızla hareket etmesi sonucu Edremit Körfezi'nin açıldığı kanısına varılmıştır.Neotectonic of Anatolia has started with the closure of neotethis during the latest Cretaceous-earliest Tertiary. During late Cretaceous, compressional regime sequized plates and ophiolithic naps were formed. During late Eocene-early Miocene this compression continued and thickness of the crust riched 60 km. This regime caused partial melting of lower crust. The results of partial melting can be seen in silisic volcanic activities in western Anatolia during this period. Until early Miocene, thickening of the crust continued and because of this, the gravitational force (Menderes Massive) subsided. Thus caused extensional regime in western Anatolia and the grabens were formed possibly mid-Miocene. During mid and late Miocene Çüngüş Basin closed complety and collision was started between Arabian and Eurasia plates. This collision caused the crust thickening in Eastern Anatolia. Force exerted from thickening of the crust, converted into the lateral forces, produced strike slip faulting on the weak parts of the Anatolian block, namely North Anatolian Fault (NAF), East Anatolia Fault (EAF). Along this faults, Anatolian blocks moved westwards. This movement of Anatolian block was stopped by Greece Shear Zone, producing a movements of plates towards Southwest, and producing extensional regime in North-South direction. This extensional regime generated volcanic activity in western Anatolia, Tertiary volcanism of Biga peninsula has started in Eocene. These volcanics consisting generally of tuffs, agglomerates and lava flows of dacites and green-gray andesites are locally intercalated with sedimentary rock of Middle Eocene age, cropping out between Biga and Çanakkale. From Upper Oligocene onwards, a new episode of volcanism has started to be effective, yielding rocks of andesitic, dacitic, trachy-andesitic and rhyodacitic composition, in the medial and eastern parts of the like peninsula and locally in the vicinity of Gökçeada and Altınoluk. The rocks have mostly been altered and locally have been silicified. Radiometric dating have yielded K/Ar ages of 28.2-23.6 My. Most of the metallic ores of NW Anatolia are related to this event. Miocene volcanism of the Biga peninsula has occurred in two episodes occupying a very large area. It has been effective Northwest of the peninsula, Bozcada and Gökçeada in Lower Miocene slowing down Late Middle-Miocene. Lava, tuff and ash of dacitic, rhyodacitic, andesitic, latitic and trachy-andesitic composition are observed. Lava flows domes, volcanic necks, ignimbrites and lahars are characteristic elements of the Lower-Middle Miocene volcanism. K/Ar ages of 13.6-22.3 have been obtained. The most important centre of eruption is the Behram caldera situated in the marine area between Behram and the Midilli island. A new episode has been effective in Upper Miocene with initial eruptions of trachy-andesitic dare coloured rocks followed by alkali olivine basalts. These crop out as dykes intruding the previous Tertiary volcanism or as lava flows in the vicinity of Ezine, Ayvacık, Çanakkale, Çan and Tavşan island. The radiometric dating yields an age of 9 My. The Eocene volcanism of the region is of calcalkaline character, ascribed to a subduction zone. Upper Oligocene, Lower-Middle Miocene volcanism is calcalkaline and hybride and ascribed to crustal thickening following the Eocene collision between the Anatolids and Pontides. The alcaline volcanism of Upper Miocene has presumably originated from the mantle. Tectonic movements can produced a rotation of blocks which can be determined from palaeomagnetic studies. Although there are some research undertaken in Western Anatolia (Kissel etal, 1986 ; Orbay etal, 1993), they deal mainly on global scale. In this study, palaeomagnetic samples collected from 47 sites (eight of them late ageing Oligocene, 35 of them early Miocene, 4 of them late Miocene), around Çanakkale-Foça and Bergama, have been analysed in order to understand the tectonics of Western Anatolia. Only two of sites were rejected because they exhibit unreliable magnetization. 386 core samples were collected and cut intol inch in length making 835 cylindrical samples, prepared for palaeomagnetic measurements. In the laboratory, first Natural Remanent Magnetization (NRM) were measured for each sites, then two pilot samples were chosen for alternative demagnetization and thermal demagnetization. Using alternative and thermal demagnetization methods, primary magnetization of the samples were obtained. If the coercivity of magnetization is high enough 25, 50, 75, 100,..., 600 (Oe or °C) steps were used, otherwise demagnetization steps were chosen as 10, 20, 30, 40,..., 250 (Oe or °C). For each step of cleaning, Magnetization magnitude, declination and inclination were measured using a spinner magnetometer, and XI cleaning steps of samples were determined from As-Zijderveld projection, Stereografic projection and Normalised magnetization diagram. In the second stage of cleaning, remaining samples of each site were cleaned using demagnetization field (or temperature) decided during the first stage of cleaning, then mean direction of magnetization of each site were calculated using Fishers statistics. The declination, inclination, precision parameter (k) and circle of confidence of 0.05 probability level (a95 ) for Natural remanent magnetization (NRM) and Remanent magnetization (RM) are given in Table 5.1. The palaeomagnetic results of two sites have not been included for analysis since they have precision parameter less than 20. In the calculation of mean direction of magnetization for a locality, firstly reverse polarities converted to normal polarities then location mean was obtained. The calculated mean palaeomagnetic pole position of this work is not significantly different from axial dipole field in 0.05 probability level. This means that, secular variation of geomagnetic field in sampled area has been companseted. Following conclusions are deduced from this study: 1-) Two sites taken from Kirazlı Village (BA16-BA17, upper Oligocene in age) on Çanakkale-Çan highway, in the Northern part of the working area, has a mean direction of magnetization of D=-36°, 1=46°. 2-) Four sites around Ezine (B1-B2-BA5-BA6, upper Miocene in age) has a mean direction of magnetization of (D=-16°, 1=64°, k=69.3, a95 =3.7). 3-) Two sites, one of which (BA4) West of Ezine and the other North of Tuzla (BA7, lower Miocene in age) a mean direction of magnetization of D=+32°, 1=57°. 4-) Five sites around Assos (B10-B11-B12-B13-B14, early Miocene) a mean direction of magnetization of (D=-25°, 1=50°, k=64.8, a95=2.7). 5-) It has been reported that (Y. Yılmaz, personal communication, 1994) there are some listric faults running E-W direction parallel the seashore of Edremit Bay (from Gülpmar to Edremit). Samples collected from 15 sites although gave reliable direction of magnetizations, they also exhibit the effect of listric faulting. xn 6-) There seems to be 2 main groups of directions in the palaeomagnetic results around Ayvalık (Southwest of Edremit Bay). The rocks consisting of each group have the same age (upper Oligocene) but they indicate different direction of rotations: The first group consist of three sites (A3-A4-BA15) and shows 15° rotation in counter clockwise. The other group indicates 29° rotation in clockwise. 7-) The samples taken area (B15, B16, B17) from Karadere region, south of Edremit has a mean direction of magnetization of D=+19°, 1=39°. 8-) The samples have taken around Altinova streem (lower Miocene in age) a mean direction of magnetization of D=-54°, 1=56°. 9-) Eigth sites (B18-B19-B20-B21-B22-B23-B24-B25, lower Miocene in age) located between Aşağıbey Village and Gökçeağıl Village, Southwest of Kozak Dağı, has a mean direction of magnetization of D=+31°, 1=57°, k=28.6 and ag5-3.7. 10-) Two sites from Dikili (BA12, BA13, lower Miocene in age) gave the following direction of magnetizations respectively 1° and 17°, and inclination 45° and 20°. 11-) Site (BAH, lower Miocene in age) from North of Bergama has a denclination of 29° in anticlockwise direction and inclination of 40°. Northwestern Anatolian Volcanics have been investigated palaeomagnetic directions by Kissel etal, (1986) and Orbay etal, (1993). Results obtained from this study are in good agreement with the results obtained above mentioned authors. Which are plotted in Figure 7.1. In this figure reverse polarities are converted into normal polarities in order to get an easy looking. In Çanakkale-Edremit Region, results obtained from this study shows a good correlation with Orbay's results, indicating 25°-34° rotation in counter clockwise direction but there is no correlation with Kissel's results except Ezine region. On the other hand, results obtained in three studies correlated with each other for the region of South of Edremit Bay. Rotation of 10°-30° in counter clockwise direction has been calculated around Alibey adası, Şeytan Sofrası, the East part of region shows 20°-30° rotation in clockwise direction. xm This region surrounding by Ayvalik-Dikili and Bergama is rotated 15°- 40° in counter clockwise direction, only exception Kozak Dağı. The result obtained from Kozak Dağı shows that there has been 31° rotation in clockwise direction. This result is significantly different than the results obtained from the area surrounding Kozak Dağı. When all the results are taken together it leads to that Northwest Anatolia has been rotated in counter clockwise direction since Neogene. This is also in agreement with GPS measurements taken during 1990-1992 which suggest that the movement of the block is in (WWS) direction (Figure 8.1). Taymaz (1990) investigated tectonic movements in Aegean Sea. He used seismologic data collected from earthquakes around Greece, Aegean sea, Bulgaria and Nortwest Anatolia (38°,42 N / 22°,28 E). He concluded that there are four major blocks separated by three faults and they extend up to the Hellenic Trench. He explained that East- West compression of Aegean Sea causes the plates to move Southwards. During this motion central part moves faster than Western and eastern parts. This movement causes a rotation of plates, clockwise direction in Western parts, counter clockwise direction in eastern parts. Kissel's results from Greece indicates a clockwise rotation, which proves Taymaz's model for the western part. The results from Orbay etal, (1993) and this study supports Taymaz's model for the Eastern part of the area. Palaeomagnetic result obtained from the area surrounding Edremit Bay, lead to a conclusion that during anticlockwise rotation of Northwest Anatolia, south of Edremit Bay rotated faster than the Northern part, as a result of this Edremit Bay was opened.Yüksek LisansM.Sc

Investigation of the neotectonic regime of Western Anatolia by means of paleomagnetic studies

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2001Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 2001Neotektonik dönemin başlangıcından itibaren, Anadolu levhasının tektonik açıdan en fazla etkilenen bölgesi Batı Anadolu'dur. Bölgenin karmaşık tektonik özelliğinden dolayı, günümüze kadar söz konusu alanda birçok çalışma yapılmıştır. Ayrıca son yıllarda, Ege'deki kuzey-güney genişlemenin başlangıç mekanizması ve yaşı üzerine yapılan tartışmalar da bölgeyi aktüel bir çalışma alam haline getirmiştir. Batı Anadolu'daki paleomanyetik çalışmalar Sanver (1967) tararından başlatılmış olup ardından Lauer (1986), Kissel ve diğ., (1988), Orbay ve diğ., (1993) ve İTÜ-İÜ paleomanyetizma projeleri (1993-2000) gelmiştir. Bu tez çalışmasında kullanılan verilerin tamamı yukarıda bahsedilen projeler dizisi neticesinde elde edilmiş ve önceki araştırmalardan elde edilen paleomanyetik verilerle topluca değerlendirilmiştir. Günümüzde dünya genelindeki paleomanyetizma çalışmaları hem volkanik kayalar hemde sedimanter kayalar üzerinde yapılabilmektedir. Ancak Türkiye'nin sahip olduğu tek paleomanyetizma laboratuvarı "KANTEK" nın mevcut ekipmanları sadece volkanik kayalarda çalışmaya izin vermektedir. Dolayısıyla bu tez çalışmasında ilgilenilen kaya türü volkanik kayalardır. Oligosen-Pleyistosen yaş aralığında yer alan Batı Anadolu volkaniklerinden daha önceki paleomanyetik çalışmalarda örneklenmeyen mevkiler örneklenmiş, bazen de bir kaç yalan mevki seçilerek sonuçların kontrolü denetlenmiştir. Bu kapsamda sırasıyla Oligosen yaşlı 12 mevki, Alt Miyosen yaşlı 63 mevki, Üst Miyosen yaşlı 57 mevki, Pliyosen yaşlı 37 mevki ve Pleyistosen yaşlı 10 mevkiden paleomanyetik numune alınmıştır. Söz konusu numuneler "KANTEK" paleomanyetizma laboratuvannda ölçmelere hazır hale getirildikten sonra standart paleomanyetik yöntemler uygulanarak her mevkiye ait ortalama mıknatıslanma doğrultusu belirlenmiştir. 208 paleomanyetik mevkiden 179'unun güvenilir mıknatıslanmaya sahip olduğu belirlenmiştir. Sözü edilen güvenilir mıknatıslanmaya sahip mevkilerden bir grubuna ait numuneler Liverpool Üniversitesi Jeomanyetizma laboratuvannda da ölçülmüş ve benzer sonuçlara ulaşıldığı görülmüştür. Bu tez çalışması çerçevesinde örneklenen paleomanyetik mevkilerden 138'ine ait numuneler için kaya manyetizması çalışmaları yine Liverpool Üniversitesi Jeomanyetizma laboratuvarında yapılmıştır. Söz konusu numuneler üzerinde termomanyetik analiz, manyetik histerizis, düşük sıcaklık süseptibilite ve eşsıcaklık ısıl kalıcı mıknatıslanma çalışmaları yapılmıştır. Buna göre, numunelere ait Curie sıcaklıkları, numune içerisindeki tek ve çok domenli dane oranlan ve mıknatıslanmadan sorumlu manyetik danelerin türleri belirlenmiştir. Sonuç olarak, Batı Anadolu volkaniklerinin mıknatıslanmasından sorumlu danelerin genellikle çok domenli manyetit olduğu ortaya çıkarılmıştır. Ortalama mıknatıslanma doğrultularının denklinasyon ve eğim açılan, bölgenin tektonik hareketleri ile ilişkilendirilmeye çalışılmıştır. Oligosen yaşlı paleomanyetik veriler Trakya'da dönme göstermezken Biga yarımadası ve güneyinde saat yönünde bir rotasyon göstermektedir. Ege'nin Yunanistan kısmına ait aynı yaşlı paleomanyetik verilerde benzer sonuçlar göstermektedir. Buna göre, Oligosen' de Batı Anadolu'nun tüm Ege ile birlikte bir bütün olarak saat yönünde bir dönme hareketi yaptığı ortaya çıkarılmıştır. Oligosen'de gözlenen saat yönü rotasyon, Alt Miyosen'de de varlığını devam ettirmiştir. Alt Miyosen paleomanyetik verileri saat yönünde ~30°'lik bir rotasyonu işaret etmektedir. Yılmaz ve diğ., (2000) Batı Anadolu'daki KD-GB doğrultulu grabenlerin graben dolgusunun yaşma bakarak, Alt Miyosen yaşında olmaları gerektiğini öne sürmektedir. Paleomanyetik verilerin gösterdiği rotasyon değeri ile KD-GB doğrultulan grabenlerin birebir uyum gösterdiği rahatlıkla görülmektedir. Bunun anlamı Oligosen-Alt Miyosen boyunca hüküm süren K-G sıkışma neticesinde K-G doğrultulu grabenler gelişti ve söz konusu grabenler günümüze gelinceye kadar saat yönünde ~30° döndü. Alt Miyosen sonuna kadar Batı Anadolu'da hüküm süren etkin tektonik kuvvetler değişerek bölgenin Üst Miyosen sonrası saatin ters yönünde dönmesine neden olmuştur. Ancak söz konusu ana rotasyon, İzmir-Eskişehir çizgisinin kuzeyinde kalan alanlar için geçerlidir. Bu hattın güneyinde kalan alan ise yine daha önceleri gibi saat yönündeki rotasyonuna Pliyosen sonuna kadar devam etmiştir. Söz konusu bu rotasyonun lokal bir hareket olmadığı ve Fethiye-Burdur fay zonunu kullanarak gelişmiş olabileceği düşünülmektedir. Kuzey Anadolu Fayı'na yakın mevkilerdeki Pliyosen yaşlı volkaniklere ait paleomanyetik sonuçlarda fayın etkisi görülmekte (saatin ters yönünde) olup, faydan uzaklaştıkça sadece kuzey-güney genişlemenin etkisi varlık göstermektedir. Öte yandan, Batı Anadolu'ya ait en genç volkanikler olan Kula volkaniklerinden elde edilen paleomanyetik sonuçlara göre, bölgede son 1.6 My' dan beri rotasyon ve/veya enlemsel bir hareketin olmadığı ortaya çıkartılmıştır. Ortalama mıknatıslanma doğrultularının eğim açılarına bakıldığında, aynı yaşlı ve birbirine yakın paleomanyetik mevkilerin mıknatıslanma doğrultularının eğim açılan arasında farklılıkların olduğu görülmüştür. Söz konusu farklılıklar, tektonik olaylar sonucu gelişebileceği gibi yermanyetik alanının dipol ekseninin eğikliğinden de kaynaklanabilir. Bilindiği gibi, yermanyetik alanını temsil eden dipolün ekseni ile coğrafik eksen arasında ~1 1.5°'lik bir açı farkı vardır. Eksen doğrultulan arasındaki açı farkının, ortalama mıknatıslanma doğrultularının eğim açısında maksimum 20°'lik bir değişime neden olabileceği hesaplanmıştır. Dolayısıyla ortalama mıknatıslanma doğrultularının eğim açılan arasındaki farkın 20° 'den büyük olması durumunda, tektonik deformasyonlardan söz etmek mümkün olacaktır. Bu tez çalışması ile Batı Anadolu'da, söz konusu eğim açılan arasındaki farkın 20° 'den büyük olan çok sayıda bölgenin olduğu saptanmıştır. Düşük mıknatıslanma eğim açısına sahip volkaniklerin geçmişte, bugünkü coğrafik enleminden daha güneyde yeraldığı ve günümüze gelinceye kadar bir miktar kuzeye ötelenmiş olduğu söylenebilir. Aynı şekilde yüksek eğim açısına sahip volkaniklerin de geçmişte daha kuzey enlemlerdeyken, güneye doğru hareket ederek bugünkü coğrafik konumunu aldığı söylenebilir. Ancak, Batı Anadolu'da bir çok bölgede görüldüğü gibi, hemen hemen yanyana duran iki paleomanyetik mevkinin birinin kuzeyden diğerinin de güneyden gelerek bugünkü konumlarım aldığını söyleyen bir tektonik model pek gerçekçi olmayacaktır. Söz konusu ortalama mıknatıslanma doğrultularının eğim açılarındaki farklılığa, lokal tektonizma sonucu gelişen listrik faylanmaların ve blok hareketlerinin neden olmuş olabileceği söylenebilir.Western Anatolia is one of the most tectonically active region of the Anatolian plate since the beginning of Neotectonic period. Many studies have been conducted in the region because of its complex tectonicframe. Furthermore, the region is subject to instense investigations recently due to high interests on the starting mechanisms and age determination of the North-South extension in the Aegean. Palaeomagnetic studies of Western Anatolia was commenced by Sanver (1967) and followed by Lauer (1986), Kissel et al. (1988), Orbay et al. (1993) and ITU-IU palaeomagnetism projects (1993-2000). The data set which was used in this thesis were compiled from the above mentioned projects, and an overall evaluation was performed by considering the palaeomagnetic results of the previous studies. Palaeomagnetism experiments can only be achieved by utilizing both volcanic and sedimentery rocks. However, the available equipments of Turkey's only palaeomagnetism laboratory "KANTEK" allows paleomagnetic experimental analysis only on volcanic rocks. Therefore, only volcanic rocks were studied in this thesis. The volcanic rocks of unsampled sites of Western Anatolia between the ages of Oligocene-Pleistocene, which hadn't been sampled at previous palaeomagnetic studies, were sampled and sometimes near sites were choosen so as control the results. From this point of view, palaeomagnetic samples were collected at 12 sites with Oligocene age, 63 sites with Early Miocene age, 57 sites with Late Miocene age, 37 sites with Pliocene age and 10 sites with Pleistocene age. In "KANTEK" palaeomagnetism laboratory, mean magnetization direction were obtained for each sites after the samples prepared for the measurements by application of standart palaeomagnetic methods. It was determined that 179 palaeomagnetic sites out of 208 have reliable magnetization. Some of the samples from the reliable paleomagnetic sites were also measured at Liverpool University Geomagnetism Laboratory and similar results were obtained. The rock magnetism studies of the samples from 138 palaeomagnetic sites were also made at Liverpool University Geomagnetism Laboratory. On the mentioned samples the thermomagnetic analysis, magnetic hysterisis, low temperature susceptibility and thermoremanent magnetization studies were applied. According to these studies, Curie temperatures of samples, the ratios of the magnetic single-domain and multi- domain grains in the samples and types of the magnetic grain responsible for magnetization were determined. Consequently, grains responsible for the magnetization of Western Anatolia volcanic rocks generally appears to be magnetite with multi-domain. xv Declination and inclination angle of the mean magnetization direction were related to the regional tectonic motions. Oligocene aged palaeomagnetic data does not show any rotation at Thrace, whereas, they indicate clockwise rotation at Biga peninsula and its southwards. The same aged palaeomagnetic data from Greece also show similar results. According to these results, it appears that Western Anatolia along with the whole Aegean underwent a clockwise rotation at Oligocene. The clockwise rotation which observed at Oligocene continued at Early Miocene, too. Early Miocene palaeomagnetic data indicate that there is an approximately 30° clockwise rotation. Yılmaz et al. (2000) proposes that NE-SW grabens at Western Anatolia to be Lower Miocene aged on the basis of age of deposits filling those grabens. It can clearly be seen that the amount of rotation estimated from the palaeomagnetic data is in agreement with the NE-SW trend of the grabens. This means that N-S trending grabens developed as a result of N-S compression dominated during Oligocene-Early Miocene, and then those grabens have rotated approximately 30° in clockwise up to now. The tectonic forces which dominate Western Anatolia until Early Miocene changed and this caused the region to rotate anti-clockwise after Late Miocene. But the mentioned main rotation was restricted to north of İzmir-Eskişehir line. The southern part of the region continued to its clockwise rotation as it happened in the past until the end of Pliocene. It is thought that this rotation might not be a local rotation but it is developed by means of Fethiye-Burdur fault zone. The effects of the North Anatolian Fault on the paleomagnetic results of Pliocene aged volcanics which are close to the fault zone (anti-clockwise) are seen, on the contrary, only the effect of N-S extension is observed far away from the fault zone. On the other hand, according to the palaeomagnetic results obtained from Kula volcanic rocks, which are the youngest volcanics of the Western Anatolia, no rotational and/or latitudinal motion were obtained since the last 1.6 Ma. Differences between the inclination angle of magnetization direction for close palaeomagnetic sites with the same age can be noticed when the inclination angle of the mean magnetization directions are studied. These differences may not only the results of tectonic motions, but also arise from the slope of Earth magnetic field dipol axis. As it is well known, there is an approximately 11.5° difference between the Earth magnetic field dipol axis and the geographic axis. It is calculated that the angle difference between the axes directions cause maximum 20° change in the inclination angle of mean magnetization direction. Therefore, it would be possible to discuss about tectonic deformations in case of more than 20° difference between the inclination angles of mean magnetization direction. In this study, many areas with inclination angle differences greater than 20° were located in Western Anatolia. It can be thought that the volcanics with low magnetization inclination angle had been located at southern latitudes in the past, and then they have been moved to their current geographic locations at northward until nowadays. Similarly, it can be thought that the volcanic rocks with high inclination angle once located at northern latitudes, then moved to southward and finally arrived at their recent geographic locations. However, a tectonic model proposing that one site moved from north to xviii south and the other moved from south to north to arrive at their recent locations for two nearby palaeomagnetic sites is not a realistic evaluation in the region of Western Anatolia. It is more realistic to state that the inclination angle differences of mean magnetization direction were caused by listric faults and block movements due to local tectonism involved.DoktoraPh.D

New paleomagnetic results from Neogene to Quaternary volcanic rocks of north of the Lake Van, Eastern Turkey

Abstract The Eastern Anatolia is an active tectonic region where the collision between the Arabian and Eurasian plates take place. Due to the subduction of Arabian plate’s oceanic lithosphere under Eurasian plate, widespread volcanism observed in large areas began in Serravallian. There is no consensus in the literature for the tectonic evolution of the region. Therefore, there are many geological and geophysical studies conducted with the intention of explaining the tectonic evolution of Eastern Anatolia by geodynamic models. Our paleomagnetism study aims to reveal the tectonic rotations in order to better understand the development of the prevailing tectonism in the region from the volcanic rocks. Paleomagnetic samples were collected from 86 sites of the Late Miocene–Pleistocene volcanic rocks located at the north of Lake Van. Isothermal remanent magnetization studies show that magnetite is the mineral responsible for magnetization in most rocks, while both magnetite and hematite are responsible for the rest of the rocks. Curie temperatures and alteration degrees of rock samples were also determined by high-temperature susceptibility (HTS) studies. In some samples, titanomagnetite component was observed in the heating phase of the HTS measurements. The absence of this component in the cooling step indicates that Ti-magnetite is transformed into magnetite by alteration. The Pleistocene volcanics show counterclockwise rotation of R ± ΔR = 13.4° ± 3.8°. The Pliocene volcanic rocks were defined in four different groups: south of Erciş Fault, north of Erciş Fault, around Muradiye and north of Van. Also, the remarkable clockwise rotation is observed in the north of Van and near Muradiye R ± ΔR = 24.4° ± 17.0° and R ± ΔR = 6.9° ± 9.4°, respectively. In addition, counterclockwise rotation (R ± ΔR = 14.5° ± 6.1°) is obtained in the southern part of the Erciş Fault, while there is no significant rotation (R ± ΔR = 0.6° ± 7.4°) on the northern side. Late Miocene volcanic rocks show no significant rotation either (R ± ΔR = 1.8° ± 13.7°). Our new paleomagnetic results indicate that the left-lateral strike-slip Çakırbey Fault, located to the east of the Erciş fault and extending roughly in the northeast–southwest direction, may be active

Identification of magnetic mineralogy and paleo-flow direction of the Miocene-quaternary volcanic products in the north of Lake Van, Eastern Turkey

One of the major challenges facing geochemistry, petrology, and volcanology researchers is the difficulty in determining the origin and paleo-flow directions of igneous and volcanic rocks. It is not possible to clearly determine origins and paleo-flow directions in areas with numerous volcanic centers. Anisotropy of magnetic susceptibility (AMS) is a valuable method that provides insights into the origins and paleo-flow directions of lavas that are complex to study. The presence of volcanic materials with thicknesses up to 1 km, coming from different sources at varied time intervals in the north of Lake Van, makes this area an ideal setting for implementing AMS in establishing paleo-flow directions. This study presents the magnetic mineralogy and AMS analysis of volcanic rocks from the Miocene to the Quaternary in the Lake Van region. We conducted isothermal remanent magnetization (IRM) and high-temperature susceptibility (HTS) studies to determine the magnetic mineralogy. IRM studies revealed that (titano)magnetite is responsible for the magnetization in most samples, while both (titano)magnetite and hematite are responsible for the rest. Alteration degrees and Curie temperatures of the rock samples were also determined through HTS measurements. There is good agreement between the anticipated directions of lava flow and our findings for nearly all volcanic rocks

2D modelling the depth of the southeastern Thrace Basin by using Bouguer gravity anomalies

This study aims to use Bouguer gravity anomalies to create a simple subsurface model of the southeastern Thrace Basin, a Tertiary depositional area located in the Northwest Turkey. Relative gravity data have been collected at over 500 points in the study area, converted into Bouguer gravity anomalies and combined with the Bouguer gravity data available in the literature for the area. The study area is subdivided into eight geological units depending on the ages and densities. A total of 12 gravity profiles were deduced from the gravity map and modelled using 2D structure, then combined into a 3D subsurface model. The observed and the calculated gravity data are highly synchronous with an RMS of ~ 0.2 mGals. Results indicate that the basin has an approximate depth of 4000 m. These findings do not agree with the other studies in literature, which will be discussed. The produced model is the most detailed shallow subsurface model of the area so far, consisting of multiple geological layers