Tectonic framework and history of Palaeozoic series evolution in Northern Caspian

The Northern Caspian and neighbouring land are situated on the south-eastern margin of the ancient East European Platform. The Caspian Syneclise is the largest negative structure delineated in the water area; the Kalmyk-Ust’yurtsky system of Palaeozoic dislocations bounds this structure from the south. The main petroleum potential of the Caspian Syneclise is related to the Later Devonian - Middle Carboniferous carbonate series. In the waters of the Kalmyk-Ust’yurtsky system of Palaeozoic dislocations, these formations are not explored with drilling. In addition, the complicated structure of the Palaeozoic section is typical here. One cannot unambiguously interpret the data from 2D seismic lines in this territory. The presented paper focuses the attention on tectonic framework and history of the Palaeozoic sequence evolution in the southern part of the northern Caspian in the context of possible oil and gas occurrence. Within the Kalmyk-Ust’yurtsky system of Palaeozoic dislocations, the Karakul’sky-Smushkovsky, North Caspian (in the water area), and South Embinsky fold and thrust zones are identified. On the results of 2D seismic data interpretation, the Palaeozoic series of the North Caspian fold and thrust zone are complicated by thrusts and reverse faults. The identified structural elements are roughly EW trending. In the Later Devonian - Middle Carboniferous period, carbonate platforms were formed in the area under investigation. In the Later Carboniferous - Early Permian time, the North Caspian fold and thrust zone was a foreland basin formed as a result of orogeny in the area of the present-day Karpinsky Ridge. By the early Kungurian time, the Caspian Basin became isolated; evaporites were accumulated there. The Palaeozoic structural level obtained its present-day structure as a result of collision processes at the end of Triassic. In the place of modern Kalmyk-Ust’yurtsky system of Palaeozoic dislocations, the mountain system was formed with further development in erosion processes up to first kilometres. The investigations conducted allowed revealing the uplifts in the North Caspian fold and thrust zone; keeping in mind their lithological and stratigraphic structure and tectonic evolution, they can be oil and gas traps