AbstractA ray-tracing modelling of seismic refraction data acquired in the 1960s has been undertaken on two north–south lines – Profile 25 in the western part of the Black Sea and Profile 28/29 crossing the Azov Sea and central part of the Black Sea. The velocity model along Profile 25 shows two domains interpreted as thin (5 km) high-velocity (sub-)oceanic crust below the deep-water part of the Western Black Sea (WBS) basin, covered by 12–13 km of Cretaceous and younger sediments, and a 39 km thick continental domain of the Scythian Platform and southernmost part of the East European Platform. They are separated by a high-amplitude normal fault, interpreted as being related to the opening of the WBS during Late Cretaceous rifting. The velocity model on Profile 28/29 shows what is interpreted as oceanic crust on the northwestern extremity of the Eastern Black Sea Basin (EBS) and thinned continental crust (Moho depths at 29 km) underlying the mid-Black Sea Ridge (MBSR) that separates the EBS and WBS. The basement of the MBSR comprises three units, which in an en echelon-like manner elevate southwards from a depth of 10–11 km beneath the Andrusov Ridge to 6 km on Arkhangelsky Ridge. An inclined seismic boundary at the Moho interface may be related to oblique rifting setting during the initial formation of the EBS.