Seismic image of the crust on the PANCAKE profile across the Ukrainian Carpathians from the migration method

Abstract

The Outer Ukrainian Carpathians (OUC) are a part of the Eastern Carpathians, which is a segment of the European Alpine Belt. The OUC is crossed by recently acquired WARR PANCAKE profile that passes from the Pannonian Basin on the SW to the East European Craton (EEC) on the NE. To get new constraints on the basin architecture of the OUC and deep structure (upper crust, Moho and uppermost mantle) along the profile we have undertaken new interpretation of the WARR data using the finite-difference migration of refracted and reflected waves. The migration is fulfilled for each shot point separately and the individual images are stacked for the image of each refracting boundary along the profile. Two main boundaries were imaged by means of the migration: the crystalline basement and the Moho. The obtained wave image of the crystalline basement in the Carpathian trough has shown the allochtonous complex of the OUC comprising stack of nappes of Neogene-Cretaceous flysch complex above the basal detachment distinguished at ∼15 km depth. Below it, at approximately 21 km depth a high reflectivity event can be distinquished, which comprises, most likely, Mesozoic-Palaeozoic metasedimentary complex related probably to collision interactions in the area of the TTZ.The migrated seismic image of the upper crystalline crust, Moho interface and uppermost mantle have shown that the crust of the ALCAPA microplate was significantly reworked by young (Neogene) tectonic and thermal processes related to formation of Pannonian back-arc basin. The Moho here is associated with a quite thick (∼10 km) package of high reflectivity and seismic heterogeneity at the depth range 25–35 km. In the subcrustal mantle there are distinguished oblique seismic boundaries gently dipping to the east/northeast below the EEC and related to recent collision processes at the southern margin of the EEC.