The crustal structure of the transition from the East Black Sea Basin to the Shatsky Ridge from reinterpretation of existing refraction seismic profiles 14-15-16

Summary We represent the results of recent ray-tracing modeling for three deep seismic sounding profiles 14, 15 and 16 acquired in the Eastern Black Sea in 1960-th. They were conducted on a system of radial profiles diverging from one common shot point in the East Black Sea Basin and crossing the Shatsky Ridge. The performed modeling showed that thin (∼ 10 km) crystalline EBSB crust, with velocities increasing from 6.5 km/s in the basement to 7.0 km/s on the Moho (20–22 km), is overlain by ∼10 km-thick sediments. The continental crust of the Shatsky Ridge of ∼ 30 km thickness comprises two layers – the upper crust (6.0–6.5 km/s) of 15-km thickness and the 10-km thick lower crust (6.5–7.0 km/s). The transition from the EBSB suboceanic crust to the Shatsky Ridge continental crust occurs dramatically, on ∼25-km interval. This transition zone runs parallel to the coastline, and is associated with Alushta-Batumi magnetic anomaly of the same (NW) strike. These could be indicative of the tectonic origin of the transition zone during the main stages of evolution of the region - at the Mesozoic closure of Tethys Ocean, during the opening of the East Black Sea Basin in Cretaceous, and during the Alpine collision tectonics.