Multidisciplinary investigation on cold seeps with vigorous gas emissions in the Sea of Marmara (MarsiteCruise): Strategy for site detection and sampling and first scientific outcome

MarsiteCruise was undertaken in October/November 2014 in the Sea of Marmara to gain detailed insight into the fate of fluids migrating within the sedimentary column and partially released into the water column. The overall objective of the project was to achieve a more global understanding of cold-seep dynamics in the context of a major active strike-slip fault. Five remotely operated vehicle (ROV) dives were performed at selected areas along the North Anatolian Fault and inherited faults. To efficiently detect, select and sample the gas seeps, we applied an original procedure. It combines sequentially (1) the acquisition of ship-borne multibeam acoustic data from the water column prior to each dive to detect gas emission sites and to design the tracks of the ROV dives, (2) in situ and real-time Raman spectroscopy analysis of the gas stream, and (3) onboard determination of molecular and isotopic compositions of the collected gas bubbles. The in situ Raman spectroscopy was used as a decision-making tool to evaluate the need for continuing with the sampling of gases from the discovered seep, or to move to another one. Push cores were gathered to study buried carbonates and pore waters at the surficial sediment, while CTD-Rosette allowed collecting samples to measure dissolved-methane concentration within the water column followed by a comparison with measurements from samples collected with the submersible Nautile during the Marnaut cruise in 2007. Overall, the visited sites were characterized by a wide diversity of seeps. CO2- and oil-rich seeps were found at the westernmost part of the sea in the Tekirdag Basin, while amphipods, anemones and coral populated the sites visited at the easternmost part in the Cinarcik Basin. Methane-derived authigenic carbonates and bacterial mats were widespread on the seafloor at all sites with variable size and distributions. The measured methane concentrations in the water column were up to 377 μmol, and the dissolved pore-water profiles indicated the occurrence of sulfate depleting processes accompanied with carbonate precipitation. The pore-water profiles display evidence of biogeochemical transformations leading to the fast depletion of seawater sulfate within the first 25-cm depth of the sediment. These results show that the North Anatolian Fault and inherited faults are important migration paths for fluids for which a significant part is discharged into the water column, contributing to the increase of methane concentration at the bottom seawater and favoring the development of specific ecosystems

Paleosismolojik bulgular ışığında Orhaneli Fayının Holosen aktivitesi, Bursa, KB Anadolu

Orhaneli Fayı, Biga Yarımadası’nda yer alan yaklaşık 30 km uzunluğunda, ters bileşeni baskın, sağ yönlü doğrultu atımlı bir faydır. Kuvaterner yaşlı Orhaneli Havzası’nın güney sınırını bu fay kontrol etmektedir. Bununla birlikte söz konusu fay aynı zamanda Tavşanlı Zonu’na ait metamorfik kayaçları, Kretase yaşlı ofiyolitik birimleri ve Neojen/Kuvaterner yaşlı sedimanları kesmekte olup hava fotoğrafl arında ve arazide belirgin çizgiselliği ve fay sarplıkları ile kolayca takip edilebilmektedir. Fay boyunca gözlenen uzamış sırtlar, ötelenmiş vadiler ve topoğrafik boyunlar, fayın aktivitesine işaret eden önemli jeomorfolojik unsurlardır. Bu çalışmada Orhaneli Fayı üzerinde gerçekleştirilmiş olan ilk paleosismolojik çalışmaların sonuçları yer almaktadır. Bu kapsamda fay üzerinde iki adet hendek açılmıştır. Serçeler ve Kusumlar olarak adlandırılmış bu hendeklerde, Tavşanlı Zonu’na ait metamorfik kayaçların fay tarafından Kuvaterner yaşlı sedimanlar üzerine itildiği belirlenmiştir. Yapılan çalışmada, Kuvaterner’de yüzey yırtılmasıyla sonuçlanmış dört büyük depremin izlerine rastlanmıştır. Serçeler hendeğinde, en eski depremin MÖ 22.000±3.200 ile MÖ 6.600±800 arasında, son depremin ise MÖ 770-415 den önce gerçekleştiği belirlenmiştir. Kusumlar hendeğinde ise, en eski depremin MÖ 6.600 ile MÖ 3.085 arasında, son olayın ise MS 650 tarihinden sonraki bir dönemde gerçekleştiği belirlenmiştir. Söz konusu eski depremler arasında tekrarlanma periyoduna ilişkin bir yorum yapılamamıştır. Bu çalışma ile Orhaneli Fayı’nın Holosen aktivitesi kanıtlanmıştır. Toplam uzunluğu 30 km olan ve iki segmentten oluşan bu fayın tek parça halinde kırılması halinde, Mw= 6,87 büyüklüğünde bir deprem üretme potansiyeline sahip olduğu belirlenmiştir

The Manyas fault zone (southern Marmara region, NW Turkey): active tectonics and paleoseismology

The Manyas fault zone (MFZ) is a splay fault of the Yenice Gönen Fault, which is located on the southern branch of the North Anatolian Fault System. The MFZ is a 38 km long, WNW–ESE-trending and normal fault zone comprised of three en-echelon segments. On 6 October 1964, an earthquake (Ms = 6.9) occurred on the Salur segment. In this study, paleoseismic trench studies were performed along the Salur segment. Based on these paleoseismic trench studies, at least three earthquakes resulting in a surface rupture within the last 4000 years, including the 1964 earthquake have been identified and dated. The penultimate event can be correlated with the AD 1323 earthquake. There is no archaeological and/or historical record that can be associated with the oldest earthquake dated between BP 3800 ± 600 and BP 2300 ± 200 years. Additionally, the trench study performed to the north of the Salur segment demonstrates paleoliquefaction structures crossing each other. The surface deformation that occurred during the 1964 earthquake is determined primarily to be the consequence of liquefaction. According to the fault plane slip data, the MFZ is a purely normal fault demonstrating a listric geometry with a dip of 64°–74° to the NNE