Sedimentology of the Karaisali Limestone and associated clastics (miocene) of the North West flank of the Adana Basin, Turkey

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Tectonic events responsible for shaping the Sea of Marmara and its surrounding region

Several basins are nested on top of one another in the Marmara Region as a result of complex series of tectonic processes. These processes are related to the evolution of the Thrace Basin, North Anatolian Shear Zone and the Sea of Marmara. The Thrace Basin evolved during the early to medial Eocene (Lutetian) as a forearc basin above the northward subducting Intra-Pontide Ocean. The basin was largely deformed and eroded during the Lutetian when the Intra-Pontide Ocean closed. Following this closure, the basin turned into a remnant forearc and continued accumulating sediments with calc-alkalic volcanic rocks. When the subducting slab finally detached and fell at the end of the Oligocene, it underwent a basin-wide deformation and erosion in the early Miocene. From medial Miocene onward, a dextral shear zone superimposed the Thrace Basin. Evolution of the shear zone began in the medial Miocene and still continues with various tectonic structures, representing the pre-peak, peak, post-peak and pre-residual stages. The Sea of Marmara probably formed during the Pliocene to Pleistocene along a variety of Riedel and P-shears of the post-peak and pre-residual structure stages

North Anatolian Fault in the Gulf of Izmit (Turkey): Rapid vertical motion in response to minor bends of a nonvertical continental transform

[ 1] The catastrophic rupture of the North Anatolian Fault east of the Marmara Sea on 17 August 1999 highlighted a need for mapping the underwater extension of that continental transform. A new bathymetric map of Izmit Gulf indicates that the fault follows the axis of the gulf with a few minor bends. Submerged shorelines and shelf breaks that formed during the Last Glacial Maximum provide markers to quantify vertical deformation. Variable tilting of these horizons reveals that vertical deformation is highest just south of the fault. A correlation between vertical deformation of the southern fault block and distance to fault bends can be accounted for by a fault dipping steeply to the south. Hence subsidence ( uplift) of the southern, hanging wall block would be expected where the fault strikes at a slightly transtensional ( transpressional) orientation to relative plate motion. Subsidence reaches about 8 mm/yr west of the town of Golcuk and might be accommodated in 1 - 2 m subsidence events during large earthquakes. That scenario is compatible with the tsunami runups and the coseismic subsidence of the southern shore that occurred in 1999. Seafloor morphology also suggests that earthquakes are accompanied by widespread gas and fluid release. The periphery of the deepest basin displays a hummocky texture diagnostic of sediment fluidization, and mud volcanoes occur west of Hersek peninsula that might be activated by earthquakes. Finally, the backscatter imagery reveals a series of lineaments midway through the gulf that are interpreted as products of the 1999 surface rupture. The seafloor is undisturbed farther west, suggesting that surface slip decreased to an insignificant level beyond Hersek. Possibly, the stress shadow from the 10 July 1894 earthquake, which was felt strongly along the western Izmit Gulf, contributed to arrest the 1999 surface rupture