Morphotectonics of the Sea of Marmara: Basins and Highs on the North Anatolian Continental Transform Plate Boundary

Abstract The Sea of Marmara is located in the North Anatolian Fault (NAF), a major continental transform plate boundary between the Eurasian and Anatolian-Aegean plates. The area is also under the influence of the N-S extensional Aegean regime. The 100 km-wide NAF zone in the Marmara region accommodates 24 mm/year dextral motion, with 70%–80% of this displacement taking place along the northern branch of the NAF, the Main Marmara Fault in the Sea of Marmara. The main morphological elements of the Sea of Marmara consists of ~ 1250 m-deep three subbasins and two NE-trending compressional highs separating the deep subbasins. The other elements are the 850-m-deep Kumburgaz Basin, the ~ 400-m-deep Imrali Basin, and the 100–200 m-deep E-W oriented gulfs or bays. The slopes connecting the shelf to the deep basins have angles ranging between 6 and 29 degrees and are incised by submarine canyons and marked by landslides scars. The basins have accumulated up to 6-km-thick sediments. They are subsiding at a rate of 5–6 mm/year and accumulating sediments at rates of 1–3 mm/year. The morphology of the Sea of Marmara is controlled by the NAF activity and by the complex basement structure, which consists of various micro-continents, suture zones, and the Eocene-Oligocene Thrace Basin. The incipient NAF activity started in the Late Mid-Miocene. Initiation of crustal extension and strain localization in the Sea of Marmara area started in the Early Pliocene. Considering the rates of subsidence and sedimentation, the present day morphology of the Sea of Marmara, with its transtensional subbasins and the intervening compressional highs between the splays of the NAF, developed mainly during the last 2.5 Ma. This geomorphic evolution is reviewed on the basis of published and unpublished data.