Architecture of the upper crust along the WARR deep seismic profile SHIELD’21 across Ukraine based on seismic and geological data

For the first time a seismic image of the East-European Craton upper crust between the Carpathians and the Dnieper-Donets Basin is presented, based on the finite-difference reflection/refraction migration processing of the SHIELD’21 deep profile results and its preliminary geological interpretation, taking into account available geophysical and geological data. The migration image shows a general domal shape of the top surface of the Archean to Palaeoproterozoic crystalline basement, which is devoid of sedimentary cover along the central part of the profile — at the Ukrainian Shield — and sloping to both sides, to the SW and NE below the sedimentary cover succession of the adjoining platform areas. The up-to-3―5-km-thick upper part of the portion of the East European Craton cross-cut by the profile is characterized by well-developed stratification and gentle folding at its flanks, while the central core is more homogeneous. High-angle faults are imaged mainly on the flanks of the Shield and dipping towards its center. The velocity model and migration image patterns agree with extensional tectonic structures identified on the terrain surface by fieldwork at the junction of the Podolian and Ros’ domains of the Ukrainian Shield. They allow the idea of a Palaeoproterozoic large-scale extension, providing a crustal heterogeneity that might have later impacted the Dnieper-Donets rift basin opening and evolution in Devonian time.