Tectono-Gravitational Detachments in the Alpine Cover of the Northern Slope of the Greater Caucasus and Western Pre-Caucasus Basin (Adygean Segment)

The Adygean segment encompasses the transition zone between the Central and Western segments of the Greater Caucasus (GC). It is located within the western part of the Laba–Malka monoclinal zone (northern slope of the GC). North of this area, the Western Kuban and Eastern Kuban basins are situated. They are separated by the Adygean uplift and generally form the southern part of the Western Pre-Caucasus basins. We have carried out geological and structural studies of the lower part of the Alpine cover (Middle–Upper Jurassic) within the Adygean segment and interpreted seismic profiles of Mesozoic–Cenozoic strata in the Western Pre-Caucasian basins. It was revealed that tectonogravitational detachments are widespread within the Adygean segment on the northern slope of the GC and in the southern part of the Pre-Caucasus basins. They occurred as a result of slipping of sedimentary layers mainly in the north direction: down the slope of the GC orogen. Our tectonophysical studies have shown that the detachments took place in conditions of reverse and normal faulting due to vertical-oblique flattening and predominantly subhorizontal stretching. We have concluded that tectonogravitational detachments were formed by the interaction of two factors: vertical uplift of the GC orogen, caused by endogenic (tectonic) reasons, and gravitational slip of geomasses from the slopes of this mountain structure. Analysis of seismic sections crossing the Western Pre-Caucasian basins has shown the widespread development of clinoforms, which are paleodeltas of terrigenous material brought from the Scythian Plate and the East European Platform. The distribution of clinoforms in Cenozoic strata of the Pre-Caucasus basins allows us to suggest that southward-directed sedimentary flows existed from the Paleocene to the Late Pliocene. Based on this, we believe that the formation of the modern GC orogen and accompanying coarse molasse began no earlier than the end of the Pliocene, probably in the Eopleistocene. The formation of tectonogravitational detachments, which is one form of manifestation of the recent orogeny of the GC, led to the development of various structures: asymmetric folds, small thrusts, domino structures, faults, ramp folds, and thrust duplexes. Along the detachments there are ramp structures of local tension and compression, which form multisized cells of lateral rock-mass transport. Such cells facilitate activation of the migration, redistribution, and localization of hydrocarbons.