The work examines the main patterns of the structure of the subsalt section of the Pre-Caspian Data on the structure of each of the sides of the depression was collected and updated, and the stratigraphic reference of the sediments was clarified, taking into account modern knowledge about the existing stratigraphic scheme of the region. Based on the analysis of numerous published and archival stock materials, schematic lithological-stratigraphic columns were constructed for the northwestern, northern, eastern, southern side zones of the depression and the zone of the Astrakhan carbonate massif, which reflect the main patterns of the structure of the sections of the given zones, and also mark their reflecting seismic horizons. Areas with active carbonate accumulation are identified, which occurred in stages during the time interval from the Middle-Late Devonian to the Early Permian. At the same time, the earliest carbonates are identified on the northwestern, northern and eastern sides of the depression and on the Astrakhan massif. Within the southern marginal zone, excluding the Tengiz-Kashagan subzone, until the end of the Early Carboniferous, terrigenous sedimentation prevailed. Moreover, predominantly terrigenous sediments accumulated within a limited area of the Matken-Ushmola subzone in the south of the basin.
The varying degrees of knowledge, existing disagreements in regional stratigraphic schemes, the degree of completeness and reliability of the identified stratigraphic units are questionable, and therefore additional core, lithological, paleontological and stratigraphic studies are needed in the future. It is quite possible to use isotope geochronology methods, especially in the southern and southern-eastern parts of the Pre-Caspian basin, where there are different views on the structure and origin of the South Emba zone. The northwestern section also requires additional research, clarification of ages and correlation of horizons.
References
1. Resheniya Mezhvedomstvennogo regional’nogo stratigraficheskogo soveshchaniya po srednemu i verkhnemu paleozoyu Russkoy platformy s regional’nymi stratigraficheskimi skhemami. Devonskaya sistema (Decisions of the Interdepartmental Regional Stratigraphic Meeting on the Middle and Upper Paleozoic of the Russian Platform with regional stratigraphic schemes. Devonian system), Leningrad, 1990, 60 p.
2. Sostoyanie stratigraficheskoy bazy tsentra i yugo-vostoka Vostochno-Evropeyskoy platformy (State of the stratigraphic base of the center and southeast of the East European Platform), Meeting proceedings, Moscow, VNIGNI, 23 –25 November 2015, Moscow: Publ. of VNIGNI, 2016, 188 p.
3. Byulleten’ Regional’noy mezhvedomstvennoy stratigraficheskoy komissii po tsentru i yugu Russkoy platformy (Bulletin of the Regional Interdepartmental Stratigraphic Commission for the center and south of the Russian Platform), Moscow: Publ. of RMSK, 2015, V. 6, 128 p.
4. Rzhonsnitskaya M.A., Eykhgorn T.F., Komissiya po devonskoy sisteme. Vypiska iz protokola zasedaniya byuro komissii ot 17 yanvarya 1999 g.: Postanovleniya MSK i ego postoyannykh komissiy (Commission on the Devonian system. Extract from the minutes of the meeting of the commission bureau dated January 17, 1999: Resolutions of the Interdepartmental Stratigraphic Committee and its standing commissions): edited by Sokolov B.S., Zhamoyda A. I., St. Petersburg: Publ. of VSEGEI, 1999, V. 31, p. 18.
5. Postanovleniya Mezhvedomstvennogo stratigraficheskogo komiteta i ego postoyannykh komissiy (Resolutions of the Interdepartmental Stratigraphic Committee and its standing commissions), St. Petersburg: Publ. of VSEGEI, 2003, V. 34, pp. 38-39.
6. Postanovleniya MSK i ego postoyannykh komissiy (Resolutions of the Interdepartmental Stratigraphic Committee and its standing commissions), St. Petersburg: Publ. of VSEGEI, 1997, V. 29, pp. 15–17.
7. Astrakhanskiy karbonatnyy massiv. Stroenie i neftegazonosnost’ (Astrakhan carbonate massif. Structure and oil and gas content): edited by Volozh Yu.A., Parasyna V.S., Moscow: Nauchnyy mir Publ., 2008, 221 p.
8. Kuandykov B.M., Matloshinskiy N.G., Sentgiorgi K. et al., Neftegazonosnost’ paleozoyskoy shel’fovoy okrainy severa Prikaspiyskoy vpadiny (na primere Fedorovskogo bloka) (Oil and gas potential of the Paleozoic shelf margin of the north of the Caspian basin (on the example of the Fedorov block)): edited by Kuandykov B.M., Shomfai A., Li Gian, Almaty: Gylym Publ., 2011, 280 p.
9. Abilkhasimov Kh.B., Osobennosti formirovaniya prirodnykh rezervuarov paleozoyskikh otlozheniy Prikaspiyskoy vpadiny i otsenka perspektiv ikh neftegazonosnosti (Features of the formation of natural reservoirs of the Paleozoic sediments of the Caspian basin and assessment of the prospects of their oil and gas potential), Moscow: Publ. of Academy of Natural Sciences, 2016, 244 p.
10. Stratigrafiya i regional’naya korrelyatsiya podsolevykh neftegazonosnykh kompleksov Prikaspiyskoy vpadiny (Stratigraphy and regional correlation of subsalt oil and gas complexes of the Caspian basin): edited by Zamarenov A.K., Moscow: Nedra Publ., 1989, 168 p.
11. Oreshkin I.V., Zholtaev G.Zh., Kulumbetova G.E., Oreshkin A.I., Characteristics of carbonate and terrigenous subsalt formations of the Caspian Depression and formation of hydrocarbon traps within them (In Russ.), Geologiya nefti i gaza, 2019, no. 4, pp. 5–16, DOI: https://doi.org/10.31087/0016-7894-2019-4-5-16
12. Pisarenko Yu.A., Ivanova L.N., Kozlovskaya O.V. et al., Local stratigraphic units of the Upper Devonian and Lower–Middle Carboniferous (In Russ.), Nedra Povolzh’ya i Prikaspiya, 2000, V. 22, pp. 3–9.
13. Iskaziev K.O., Khafizov S.F., Lyapunov Yu.V. et al., Pozdnepaleozoyskie organogennye postroyki Kazakhstanskogo segmenta Prikaspiyskoy vpadiny (Late Paleozoic organogenic structures of the Kazakhstan segment of the Caspian basin), Moscow: LENARD Publ., 2019, 250 p.
