Methodology and results of integrated airborne geophysical surveys in the junction zone of the East European Platform and the Scythian Plate

In 2011, work is being completed on the project “Integrated airborne geophysical surveys (airborne gravimetry and aeromagnetic prospecting) at scales of 1:50 000–1:100 000 within map sheets M-37-XXII–XXIV, XXIX, XXX, XXXIV–XXXVI, M-38-XIX, XXV–XXVII, XXXI–XXXIV, L-37-III–VI, IX–XII, L-38-I–IV, VII–X, XIII–XV, XX–XXII”, undertaken by GNPP Aerogeofizika under State Contract No. 28 dated 14 December 2007. The objective is to establish a modern geophysical basis for geological mapping, investigation of the structural, tectonic and deep subsurface architecture, and assessment of the raw-material resource potential of the central part of the Southern Federal District.

Under the contract, integrated airborne geophysical surveying covered 134 320 km². The results were used to compile a set of maps of the original geophysical fields at a scale of 1:200 000, including:

• a map of the anomalous magnetic field;
• a map of the local component of the anomalous magnetic field;
• a map of free-air gravity anomalies;
• maps of Bouguer gravity anomalies with terrain corrections (for intermediate-layer densities of 2.3 and 2.67 g/cm³);
• a map of relative terrain elevations.

Physical and mathematical modelling and integrated interpretation of the acquired data supported structural and tectonic mapping of the area through:

1. Mapping the relief of the crystalline basement surface and resolving its internal structure.
2. Refining fault locations and assessing their influence on conditions for hydrocarbon-trap formation, hydrocarbon migration and reservoir properties, including refinement of the distribution boundaries of thrust zones in the sedimentary cover.
3. Investigating the morphology of structures in the sedimentary cover.
4. Refining the location and structure of the tectonic contact between the East European and Scythian platforms along the interval between the known Northern Donbas Thrust and the Astrakhan Thrust (the North Donets–Astrakhan Thrust), including the possible identification of subthrust hydrocarbon accumulations along its strike.
5. Identifying the southwestern continuation of the hydrocarbon-bearing Middle–Upper Devonian–Lower Carboniferous barrier-reef structures of the marginal Caspian zone in the Saratov Volga region, which plunge beneath the marginal thrust.
6. Investigating the internal structure of the folded Palaeozoic basement sequences of the Karpinsky Ridge to identify possible carbonate reef bodies that may act as fractured reservoirs for hydrocarbon accumulations.
7. Determining the extent of the Carboniferous coal-bearing sequences of the Donbas and the nature of their interaction with the Palaeozoic deposits of the Karpinsky Ridge.