On the formation mechanisms of folding and mud volcanism in the Sorokin trough

Abstract. There are two points of view on the geology and the nature of folding of the Sorokin trough. The proponents of the first one consider the folds as diapirs, developed within the Maikop filling of the marginal trough during lateral compression from the side of the Shatskiy swell and the Tetyaev uplift. The proponents of the second one interpret a series of fold-thrust dislocations at the base of the continental slope as structures of an accretionary wedge of dislocated sediments deposited on the suboceanic crust in the pseudosubduction zone of the Black Sea lithosphere under the Crimea.

Objective. To clarify the understanding of the structure of the Maikop series sediments within the Sorokin trough, taking into account that the trough is one of the most promising areas of the Black Sea region for hydrocarbon exploration.

Materials and methods. Based on the high-resolution seismic data obtained during the geological survey on sheets L-36-XXXV, XXXVI, a seismostratigraphic subdivision of sedimentary filling of the Sorokin trough was performed, faulting and folding in the rocks of the Maikop-Early Pleistocene formation were studied.

Results. The gravitational nature of folding in the rocks of the Maikop series within the Sorokin trough is shown. The South Crimean and South Kerch olistostromes are outlined and the surfaces of the detachment faults at the base of the olistostromes, in the lower part of the section of the Maikop series, are traced. In the upper part of the continental slope, the surface of the main scarp at upper edge of the olistostromes is mapped; below, giant olistoliths of the block rotational slides of delapsive part (sliding part) of the South Crimean and South Kerch olistostromes are located.

Near the boundary of the detrusive part (extrusive part) of the olistostromes, under lateral pressure from the weight of the olistoliths of the delapsive part, the slabs of landslide blocks are squeezed upward, forming a series of thrust sheets. At the outer boundary of the detrusive part of the olistostromes, asymmetric folds of fault propagation are formed. Zones of gas saturation of sediments associated with lateral migration of gases along rupture dislocations are confined to local uplifts of the top relief of the Maikop clays above growing folds of propagation. The development of mud volcanism is associated with AHFP zones and fluid accumulations: the formation of feeder channels, collapse depressions, mud pies or volcanic cones, fluid migration zones, gas seeps, etc.

Conclusion. The Sorokin Trough is one of the most promising areas of the Black Sea region for hydrocarbon exploration. The obtained information about the gravitational nature of folding in the trough should be taken into account when assessing the prospects for oil and gas potential and developing a strategy for developing the hydrocarbon potential of the Black Sea.

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