Abstract:
The offshore Akcakoca-Amasra area is located in the Black Sea basin which contains two subbasins; the Western and Eastern Black Sea basins. The Western Black Sea basin is formed as a result of rifting of the Moesian Platform in Early Cretaceous. The rifting is followed by the closure of the Neotethys Ocean in the Middle Eocene, which resulted in the formation of the Pontide fold and thrust belt located in northern Turkey. In this study, eight seismic reflection profiles are interpreted to determine the subsurface structural geometry and tectono-stratigraphic evolution of the offshore Akcakoca-Amasra area.. The stratigraphy of the study area is determined based on composite well log of the Akcakoca-1 wildcat well drilled in the study area. A velocity model is constructed based on sonic data from the Akcakoca-1 well. Relative acoustic impedance is applied to each seismic profile to amplify the seismic reflections in order to trace seismic horizons, where the resolution is very low. Structural interpretation of the eight seismic reflection profiles suggests that a major décollement surface was developed during the Pontide Orogeny in the Late Cretaceous Maastrichtian–- Paleocene Akveren Formation at the limestone clay-shale intraformational transition. The decollement uses the syn-rift normal faults to develop ramp-flat thrust fault geometry. A well-developed duplex structure is also present along the seismic lines.. The number and size of the horse structures within the duplex decrease towards the northeast This suggests that the intensity of the compression is decreasing from southwest to northeast. In the northeastern part of the study area, a rotational landslide is observed along the seismic lines around offshore Amasra. The failure surface of the landslide possibly coincides with the décollement surface of the Pontide thrusting. This rotational landslide may have been triggered by historical earthquakes in and around the study area
