Geology of the Paleotetis units at the northern part of Edremit Bay

İnceleme alanı Kuzeybatı Anadolu’da Biga Yarımadası’nın güneyinde, Edremit Körfezi ve kuzeyinde yer alan Kazdağ ve çevresini kapsar. Kazdağ Grubu, amfbolit-granulit fasiyesinde metamorfik bir istiftir.  Kazdağ Grubu üzerinde, bir sıyrılma fayı dokanağı ile yeşil şist fasiyesinde metamorfik birimlerden oluşan Karakaya Karmaşığı bulunur. Kazdağ Grubu, okyanus kabuğu, üzerinde gelişen okyanus platosu çökel ve volkanikleri, Karakaya Karmaşığı, riftt çökelleri, denizaltı-dağı, denizaltı platosu, hendek çökelleri, dalma-batma gerisi havza çökelleri temsil eden bir eklenir prizmadır. Kazdağ Grubu ve Karakaya Karmaşığı Paleotetis Okyanusu’nun Permo-Karbonifer’de oluşumu ve Triyas’ta kapanmasının hemen hemen tüm aşamalarını temsil eder. Anahtar Kelimeler: Paleotetis, Kazdağ Grubu, Karakaya Karmaşığı, jeodinamik evrim.Study area is located to the south of the Biga Peninsula, NW Anatolia. It includes the Edremit Bay and the Kazdağ Group to the north. The rock groups represent a geological period starting from the Carboniferous to present. On the basement a metamorphic series in amphibolite-granulite facies take place. These series form the Kazdağ Group itself and are made up of the Babadağ Formation, Sarıkız Formation, Kavurmacılar Formation and Altınoluk Formation. A detachment fault and the metamorphic Karakaya complex (green schist facies) take place on the Kazdağ Group. To the east, the Karakaya Complex starts with the Fazlıca, Kınar and Kalabak units, which contain shale, schist, fillate, basalt and marble, on a Palaeozoic granodiorite basement. These units are overlain by the units of Nilüfer, which is made up of tectonically thrusted spilits, and Tepeoba, which is made up of felsic fillate and tuffs, respectively. The unit Hodul passes laterally into the unit Nilüfer and it is made up of arkozic sandstone, rare spilit and chert alternations. On top of these formations, the unit Çal is located with a tectonic contact and it contains Permian-Trias limestone blocks in a size of a mountain. The study area forms the pieces of Palaeotethys ocean dominated between Carboniferous and Triassic. The rocks of the Kazdağ Group form the Laurassia part of the ocean crust while the Karakaya Complex represents the southern environments of the south-dipping oceanic crust. These environments include the sea-mount (Nilüfer unit), accretional prism (Hodul unit), marginal basin (Tepeoba unit) and passive Cimmeria margin of this basin (Fazlıca+Kınar+Kalabak). The Laurassia and Sakarya continents collided during Middle-late Triassic and the units between these continents formed the Karakaya Complex in the form of tectonic slices.Keywords: Paleotethys, Kazdağ Group, Karakaya Complex, geodynamic evolution

GÜNEY TRAKYA SAHİLLERİNİN DENİZEL PLEYİSTOSEN ÇÖKELLERİ VE PALEOCOĞRAFYASI

Orta-geç Pleyistosen'de güney Trakya sahilleri, bugünkü çizgisinden daha içeride bir çizgiye çekilmesine neden olan bir transgresyonun etkisi altında kalır. Bu dönemde Gelibolu yarımadasını Bolayır ve Eceabat boğazlarından aşarak Eski Marmara denizini bir adalar denizine çeviren bu transgresyon sonucu oluşan sahil çizgisinde, Ostrea edulis, Loripes lacteus bolluk zonu ve yalıtaşı işaretçi seviyelerinin de içinde yer aldığı kırıntılı kıyı çökelleri depolanır. Farklı paleoçökelim alanlarında depolanan birimler; bu dönem ve sonrasında, bir taraftan tektonik olaylarla yükselirken diğer taraftan da regresif karakter kazanarak, tekrar denize taşınmaya başlar. Bu denizel depolardan günümüze kadar korunabilenler, depolanma alanlarının paleocoğrafyası ve tektonik etkilerden kaynaklanan olaylar nedeniyle, farklı yüksekliklere sahiptirler. Bölgesel yükselmenin izlerini taşıyan denizel depolar, Eski Marmara denizinin sahil fasiyesleriyle temsil olan Marmara formasyonunu oluşturur. Bu çökelleri yer yer örten, Cardium sp. ve Murex sp. içeren Holosen yaşlı genç depoların da bugünkü deniz seviyesinden yükselmiş olması, bölgede sıkışma kontrollü tektonik rejimin halen sürdüğünü göstermektedir

TRAKYA'DA SENOZOYİK VOLKANİKLERİNİN PALEOMANYETİK ÖZELLİKLERİ VE BÖLGENİN TEKTONİK EVRİMİ

Trakya üzerinde Eosen-Oligosen, Oligo-Miyosen ve Pliyo-Kuvaterner yaşlı volkaniklerde üç farklı tektonik rejimin etkileri görülür. Bunlardan ilki Oligosen'de saat yönünde 15° olan dönmedir. Bu dönme, Oligo-Miyosende Rodop-Pontid İç Okyanusunun kapanmasına neden olan kıta-kıta çarpışmasının sonucu olmalıdır. İkinci olarak Orta-Geç Miyosen'de Trakya, kuzeyde Trakya Renç fay zonu, güneyde Ganos fay sistemi ile sınırlı alanda saat yönünün tersinde 39° dönmüş, Trakya Renç fayları üzerinde sağ yönlü bir hareket meydana gelmiştir. Bu hareketin ardından Pliyosen'den günümüze KAF'ın hareketiyle Anadolu Bloğu, Trakya Bloğu'yla karşılaşmış, Trakya'yı hortlayan ganos fayının kuzeyinde kalan yaklaşık 40 km. uzaklıkta bulunan bir zon boyunca sağ yönlü hareketle makaslayarak sıkıştırmıştır. Bu hareketin etkisiyle de Trakya'da Hisarlıdağ-Tekirdağ doğrultulu bir eksen boyunca, kuzeyde kalan 39° dönmüş bazaltlar saat yönünde ortalama 30° dönerek ilksel konumlarına yaklaşmışlardır. Ganos fayının güneyinde ise Geç Miyosende saatin ters yönünde 39° dönen Gelibolu bloğu KAF'ın etkisiyle sıkışmaya başlamış, Saroz Körfezi boyunca 20° daha aynı yönde dönmüştür. Bu nedenle Saroz bloğu bir dönem batıya kaçarakKarlıova benzeri bir yapıyı ortaya çıkarmıştır. Bu esnada bugünkü haline benzer bir yapı kazanan körfezin-kuzey sınırı boşalan alanı karşılayan oblik normal faylarla karakterize olan gerilmeli bir döneme girmiştir

Kinematics and evolution of the northern branch of the North Anatolian Fault (Ganos Fault) between the Sea of Marmara and the Gulf of Saros

The WSW-ENE-trending Ganos Fault is a dextral strike-slip fault running parallel to and southwest of the West Marmara Trough and south of the Saros Trough. Dextral structures started evolving in the early Miocene, and at this time the Ganos fault system developed from a part of the Thrace-Eskisehir fault system. Beginning in the late Pliocene (similar to 3.5 Ma), the North Anatolian transform fault propagated into the Marmara region and captured the Ganos Fault. Subsequently, this fault has accommodated the westward movement of the Anatolian Block. Because of the curvature of the microplate boundary in this area, the Ganos fault system has tended to rotate counterclockwise. Farther west in the Gulf of Saros, the strike-slip motion was accommodated by a new fault on the northern margin of the gulf, rather than along the northern coast of the Gelibolu Peninsula as previously thought. This interpretation differs from previous assessments of the position of the northern strand of the North Anatolian fault (Marmara segment) in the Marmara Sea and in the Gulf of Saros. The role of the Ganos Fault proposed in this paper is considerably different from that proposed by earlier studies. While the revised orientation of the North Anatolian fault on land is about 7degrees different than specified by previous authors, at sea it is different by similar to 32degrees counterclockwise and similar to 23degrees clockwise in the West Marmara and Saros submarine depressions, respectively. The revised position of the Ganos Fault in the Marmara Sea, derived from shallow and conventional seismic reflection data, calls into question the validity of evolutionary models previously used in kinematic and stress-failure analyses. In particular, it is not possible to regard the Marmara Sea as a pull-apart basin and the Gulf of Saros as a transtensional half-graben. Furthermore, palinspastic maps taking into account the revised position of the Ganos Fault and GPS slip vectors support the idea that a dextral master fault is present to the north of the Saros Trough with a sinistral oblique fault dominated by normal offset (Gelibolu Fault) to its south. The Gelibolu Fault is reactivated in a limited region. (C) 2002 Elsevier Science B.V. All rights reserved

Evolution of the middle strand of North Anatolian Fault and shallow seismic investigation of the southeastern Marmara Sea (Gemlik Bay)

The Gemlik Bay is developed as a pull-apart basin during the late Pliocene-early Pleistocene mainly controlled by west-trending dextral strike-slip faults along the middle strand of the North Anatolian Fault zone, with the NW-trending Thrace-Eskisehir Fault playing secondary role. The North Anatolian Fault reached the eastern Marmara Sea similar to 3.5 Ma ago, where its middle strand intersected the Thrace-Eskisehir Fault. GPS slip vectors measured on the Armutlu and Mudanya blocks show a displacement of 7-8 km during the last 3.5 Ma. The middle strand of the North Anatolian Fault zone has lower tectonic activity than the northern strand. Because uplift of the southeast Marmara Sea region has been continuous since the late Pliocene, the presence of fluviatile, lacustrine and deltaic environments in the Gemlik pull-apart basin over the same period supports a lower lever of tectonic activity. The transgressive Marmara Formation was deposited on top of these fluvio-lacustrine deposits following the Mediterranean inundation at similar to 600 ka via the Strait of Canakkale. The Gemlik basin was affected both by two major sea-level falls at 160-132 and 24-11 ka, and minor short-lived sea-level variations, as a result of becoming a lacustrine setting five times since similar to 600 ka. During these lowstands, stacked delta successions were deposited around the lake and on the transgressed shelves of the Marmara Sea. (C) 2002 Elsevier Science B.V. All rights reserved

Characteristic features of the North Anatolian Fault in the eastern Marmara region and its tectonic evolution

Shallow seismic profiles are used to image the tectonic and stratigraphic setting in Izmit Bay, eastern Marmara Sea. Four seismic units were detected in the sediments of Izmit Bay, which carry the effects of the tectonic uplift and global sea-level variations. The area appears to be a negative flower structure controlled by the northern branch of the North Anatolian Fault. In the late Pliocene the North Anatolian Fault reached Marmara Sea as a master fault. Smallscale faults were evolved around the master fault under a regime of dextral shear. The northward bending of the master fault gave rise to en-echelon faults, opening the sub-basins in Izmit Bay as releasing bends. The secondary faults which developed as low-angle oblique to the master fault are also the products of dextral shear. To the south, short dextral ENE-WSW trending faults are interpreted as "P"-shears, while to the north, dextral WNW-ESE trending faults represents 'R'-shears. These faults absorbed the deformation at the western end of the ruptured zone during the Izmit Earthquake (August 17, 1999), causing the migration of failure stress westward. (C) 2002 Elsevier Science B.V. All rights reserved

Tsunami of Sarkoy-Mujrefte 1912 earthquake: Western Marmara, Turkey

One of the largest earthquakes in the Balkans is the 09.08.1912 (01:29:00 UTH) Sarkoy-Murefte Earthquake which occurred on the active Ganos fault zone (Ms=7.4). The eastern termination of the associated faulting is in the Marmara Sea. On the basis of archiving and library studies, geological field surveys and offshore investigations, the 1912 earthquake produced a tsunami. The mechanism of this co-seismic tsunami may be assigned to an underwater failure along the southern slopes of the Tekirdag Trough rather than a seabed dislocation

Tectonic elements controlling the evolution of the Gulf of Saros (northeastern Aegean Sea, Turkey)

Tectonic elements controlling the evolution of the Gulf of Saros have been studied based upon the high-resolution shallow seismic data integrated with the geological field observations. Evolution of the Gulf of Saros started in the Middle to Late Miocene due to the NW-SE compression caused by the counterclockwise movement of the Thrace and Biga peninsulas along the Thrace Fault Zone. Hence, the North Anatolian Fault Zone is not an active structural element responsible for the starting of the evolution of the Gulf of Saros. The compression caused by the rotational movement was compensated by tectonic escape along the pre-existing Ganos Fault System. Two most significant controllers of this deformation are the sinistral Ganos Fault and the dextral northern Saros Fault Zone both extending along the Gulf of Saros. The most important evidences of this movement are the left- and right-oriented shear deformations, which are correlated with structural elements, observed on the land and on the high-resolution shallow seismic records at the sea. Another important line of evidence supporting the evolution of this deformation is that the transgression started in the early-late Miocene and turned, as a result of regional uplift, into a regression on the Gelibolu Peninsula during the Turolian and in the north of the Saros Trough during the Early Pliocene. The deformation on the Gelibolu Peninsula continued effectively until the Pleistocene. Taking into account the fact that this deformation affected the Late Pleistocene units of the Marmara Formation, the graben formation of the Gulf of Saros is interpreted as a Recent event. However, at least a small amount of compression on the Gelibolu Peninsula is observed. It is also evident that compression ceased at the northern shelf area of the Gulf of Saros. (C) 1998 Elsevier Science B.V. All rights reserved