Cem Gazioğlu

Morphologic features of the Marmara Sea from multi-beam data

Abstract The bathymetrical image of the Marmara Sea (NW of Turkey) was prepared, using data from mainly multi-beam surveys and from various other sources. The Marmara Sea presents a unique and complicated morphological system, which is mainly controlled by the active tectonic regime of the North Anatolian Fault Zone (NAFZ). The sub-bottom morphology of the Marmara Sea consists of a wide shelf area (55% of the total area) and the Marmara Trough, which includes the slopes, ridges and deep basins. The four basins separated by ridges constitute the E–W trending Marmara Trough in an elliptical form. Submarine canyons and landslides constitute the secondary morphological units of the Marmara Sea. The angle and the shape of the slopes are variable in different parts of the Marmara Sea. The linear-shaped slopes bounding the Cinarcik Basin (eastern extremity of the Marmara Sea) and off the Ganos Mountain System (west of Marmara Sea) are characteristic with their high gradient, and resulted from strike–slip fault. The curve-shaped slopes with low angles are considered to be associated with normal fault. E–W-aligned lineaments are morphological expressions of strike–slip faults and can be traced from the Ganos Mountain System through Cinarcik Basin, cutting through the basins and ridges in the western Marmara Trough, and bounding the Cinarcik Basin at the slope–basin transitions. These lineaments reflect a new rupture of NAFZ and must have occurred after the formation of the Marmara Trough.

Active tectonics of the İzmit Gulf (NE Marmara Sea): from high resolution seismic and multi-beam bathymetry data

Abstract Several active faults were determined in the Gulf of Izmit, using high-resolution shallow seismic and multi-beam bathymetry data. One of them is a buried fault (Fault 2), following central axis of the gulf, which forms the current morphology within its releasing and restraining bends. Releasing bends control the current morphology of the sub-basins. Also restraining bends form folds in the central basin and a thrust in the western basin. A left step over between two strike-slip faults (Faults 2 and 11) creates a transpressional area. Therefore, Hersek and Catal deltas are uplifted. It is determined that Fault 2 could not be related to the origination of the gulf because it cuts all basins and ridges, thus, present geometry of the Fault 2 is not suitable for the initial formation of the gulf. From this point of view, the Fault 2 is initiated recently compared to the whole North Anatolian Fault Zone (NAFZ) in the Marmara Sea. Therefore, Fault 2 is recognised as a new rupture of the NAFZ probably active since the end of the last glacial ice period.

Morphological Features of Major Submarine Landslides of Marmara Sea Using Multibeam Data

Abstract Recent bathymetric surveys help us to understand morphological features of the Marmara Sea. Marmara Sea has unique and complex morphological features and active tectonics. In this study, morphologic features of major submarine landslides of the Marmara Sea were studied using advanced visualization and geomatic systems (digital terrain models, DTM; geographic-information systems, GIS; image-processing systems; high-resolution seismic and bathymetric data). The high-angle continental slopes of the Marmara Sea are produced by submarine landslides and slumps, which have potential tsunamis generations. In this study, tectonically active major submarine landslides were investigated in the Marmara Sea. Three of them are observed along the slopes, one is on the Eastern Ridge and the fifth forms the Western Ridge of the Marmara Sea. They are interpreted as rotational and translational slides, debris flows, and mudflows controlled by slope and tectonic activity. On the northern slope of Çınarcık Basin, rotational slide and debris flows, which are activated by faults, affect the current shape of this slope. Hence, we interpret that the present morphology of the slopes of the Marmara Sea may not be only controlled by faults but also the landslides. On the other hand, mudflows in Tekirdağ Basin and in the Marmara Sea entrance of Izmit Bay (Çınarcık Basin) may be controlled by slope inclination and sediment supply rather than tectonics. Another mudflow on the Eastern Ridge initiated by the inclination of the ridge by a reverse fault in the northwest side of the ridge, thus, slope inclination controlled by tectonic activity affects the origination of this landslide. One of the largest landslides in the Marmara Sea forms the Western Ridge as a translational slide. Its initial shape has been destroyed by the new rupture of the North Anatolian Fault Zone, thus, it may be one of the oldest submarine landslides of the Marmara Sea.