Material composition of the kursov’s assise of the vendian period of the Mirnin outshot of the Nepsk-Botuobinsk anteclise according to the results of the core material study

In this work, the object studied is the terrigenous and carbonate rocks of the Kursov’s assise of the Nepsk horizon of the Botuobinsk facies zone of the Mirnin outshot of the north-eastern part of the Nepsk-Botuobinsk anteclise. In recent years, in the course of active geological exploration work in the region, high quality core material appeared. This material was studied at the macro and micro levels, which made it possible to obtain new data on the material composition. Based on the detailed lithological description and petrographic core study, for the first time, the author gives a description and justification of the division of the Kursov’s assise into three lithological packs: low clay sand, middle carbonate clay and high carbonate clay sand. The lithological properties of the studied section reflect the characteristics of the Vendian deposition of sediments in the south of the Siberian paleocontinent. The accumulation of sandstones of the Kursov’s assise was facilitated by the weathering of magmatic rock of acidic and medium composition; the destruction products that came from the north-western part to the south-eastern part of the NepskBotuobinsk anteclise in the modern plan. In the upper-section of the Kursov’s assise, the gradual increase in the maturity of terrigenous rocks, which is associated with the duration of their transportation and repeated redeposition, is observed. The carbonate microbial formations of the middle pack of the Kursov’s assise are the first witnesses to life in the Vendian paleobasin. Their characteristic feature is the magnesia impurity.

lithology, Kursov’s assise, Nepsk horizon, Vendian, Mirnin outshot, Nepsk-Botuobinsk anteclise, Eastern Siberia

1. Mel ’nikov N.V. Vend-kembrijskij solerodnyj bassejn Sibirskoj platformy (Stratigrafiya, istoriya razvitiya) [Vendian-Cambrian salt pool of the Siberian platform (Stratigraphy, history of development)]. Novosibirsk, SB RAS Publ., 2009, 148 p. (in Russian)

2. Ko tova L.N., Podkovyrov V.N., Graunov O.V. Lithogeochemistry of fine-grained Vendian clastic rocks of the Nepa dome, Siberian Platform. LITHOSPHERE (Russia), 2016, (1), рр. 74–87. (In Russian)

3. Kuznetsov V.G., Litologiya. Osnovy obshchey (teoreticheskoy) litologii [Lithology. Fundamentals of general (theoretical) lithology], Moscow, Nauchnyy mir Publ., 2011, 360 р. (in Russian)

4. Ma slov A.V. Osadochnye porody: metody izucheniia i interpretatsii poluchennykh dannykh: uchebnoe posobie [Sedimentary rocks: methods of study and interpretation of obtained data: study manual]. Ekaterinburg, Izdatel’stvo UGGU, 2005. 289 p. (in Russian)

5. Pettidzhon F.Dzh. Osadochnye porody [Sedimentary rocks]. Mosсow, Nedra, 1981, 752 p.

6. Resheniya chetvertogo Mezhvedomstvennogo regional’nogo stratigraficheskogo soveshchaniya po utochneniyu i dopolneniyu stratigraficheskih skhem venda i kembriya vnutrennih rajonov Sibirskoj platform [Decisions of the fourth Interdepartmental Regional Stratigraphic Meeting to clarify and supplement the Vendian and Cambrian stratigraphic schemes of the inner regions of the Siberian Platform]. Novosibirsk, CIIGGIMS, 1989, 64 p. (in Russian)

7. Frolov V.T. Litologiia [Lithology]. Мoscow, Moskovskii gosudarstvennyi universitet, 1992, book 1, 336 p. (in Russian)

8. Shemin G.G. Geologiya i perspektivy neftegazonosnosti venda i nizhnego kembriya central’nyh rajonov Sibirskoj platformy (Nepsko-Botuobinskaya, Bajkitskaya anteklizy i Katangskaya sedlovina) [Geology and oil and gas potential of the Vendian and Lower Cambrian in the central regions of the Siberian platform (Nepsko-Botuobinskaya, Baikit anteclises and Katanga saddle)]. Novosibirsk, SB RAS Publ., 2007, 467 p. (in Russian).

9. Einsele G. Sedimentary basins: Evolution, facies, and sediment budget. Berlin: Springer-Verlag, 2000, 792 р.

10. Lebedev M.V. Facial unconformities and facial series in the sequence stratigraphy. Oil and Gas Studies. 2018;(6):24-32. (In Russian) https://doi.org/10.31660/0445-0108-2018-6-24-32.