The Sakarya River is among the largest fluvial systems of the southern Black Sea basin, draining most of NW Anatolia. The river crosses the high relief of the Pontide mountain range through successive narrow gorges and strike-slip basins formed by the North Anatolian Fault (NAF) System. We have investigated this fluvial record along the course of the main river channel at its lower reaches. The study site is located south of the Adapazarı Basin, ~50 km inland from the Black Sea, where remnant floodplains are preserved as a three-step terrace staircase resulting from continuous uplift to the south of the NAF. The combination of high resolution mapping with a detailed luminescence (OSL and p-IR-IRSL) and radiocarbon geochronology has shed light on changes in the level of the Black Sea and in the hydrological system during the late Pleistocene to recent. The last glacial period is represented by the highest terrace (T3) indicating deposition during marine isotope stage (MIS) 3 in between two low stands of the Black Sea. Following a long-term erosional period initiated prior to last glacial maximum (LGM), the initiation of the deposition (T2) was synchronous with the proposed catastrophic sea level rise of the Black Sea (cal. C14 9.3 ka BP) which continued throughout the Holocene until the Roman warm period (1.8 ka BP). The late-Holocene to recent morphological evolution of the region is marked with two sequential erosional and depositional (T1 and T0) periods, which can be correlated with the well-documented historical climate shifts affecting the hydrological system. These results reveal that the erosional and depositional periods on the Sakarya River floodplain are controlled by major sea level changes and climatically induced fluctuations in discharge and sediment supply.

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<p>The study area (40-40.45°N and 30-32.15° E) exhibits a high topography (1200-1800 m elevation) and bounded by the Galatean Massif at east, Pontide Mountain Range to the north, the Central Anatolian Plateau to the south and the Marmara Sea to the west. The region is actively been deformed and dissected by the active branches of the dextral strike slip North Anatolian Fault Zone (NAFZ) and the Sakarya River (SR) system. We have investigated the depositional terraces formed along the main course and the major tributaries of the SR to reveal the dynamics of the terrace formation by climate, sea level changes and also to quantify the variations in rate of vertical deformation within the current geodynamics of the NW Anatolian Block. The geometry of the main river (1) and its tributaries (4) allow us to determine the spatio-temporal variations in four vertical (100 km) and three along fault sections (200 km) since the last ~150 ka.</p><p>Up to date, we have mapped 23 distinct evenly scattered multi-step terrace staircases along the main river course and its 6 major tributaries. Mapping is aided with high precision rtk-GPS profiling and SfM photogrammetry using UAV. The dating is carried by luminescence geochronology (OSL and p-IRIR) to constrain the timing of the formation and also abandonment of each depositional terrace step.</p><p>The results show that the focus region is under control of vertical deformation at a rate of 0.6-0.7 mm/year regardless from the distance to the main strand of the NAFZ. There is also evidence that this rate has been decelerated from ~1.0-1.1 mm/year since the last 100 ka. The distinct variations in the calculated uplift rates along the profiles reveal apperant southwards tilting in between the active branches of the NAFZ and also within the block.</p><p>This study is funded by TUBITAK 117Y426 project grant. </p>