Geologicheskii Vestnik

Fieldwork was conducted in 2025 in the northern West Magnitogorsk zone of the Southern Urals, northwest of the Mansurovo village in the Uchalinsky District of the Republic of Bashkortostan. The study revealed the presence of an angular and azimuthal unconformity between Ordovician-Silurian siliceous-clayey sediments and the clastic rocks of the Mansurovo Formation. This conclusion is supported by dating of detrital zircon extracted from graywackes in the lower part of the Mansurovo Formation. The concordant age determined from five grains in one of three samples was 415.6 ± 5.3 Ma, corresponding to the middle part of the Lokhkovian Stage.

These results allow us to limit the previously proposed Silurian age for the lower part of the Mansurovo Formation to the Przhidolian division of the Silurian.

stratigraphy, Devonian section, formation, stratum, well, Sol-Iletsk uplift, Caspian Depression

• Artyushkova O.V., Kondratenko V.F. (2012) Discovery of Emsian conodonts Amydrotaxis murphyi Savage in the Preurals and South Urals. Proceedings of the XV All-Russian Micropaleontological Conference "Modern Micropaleontology". Moscow, 2012 Р. 194–197. (In Russian).
• Antipov M.P., Bykadorov V.A., Volozh Yu.A., Dnistryanskiy V.I., Ivanova N.A., Kashirskih M.F., Ofman I.P., Parasyna V.S., Heraskova T.N. (2013) Orenburg tectonic node: the geological structure and oil and gas potential. Moscow: Nauchnyy mir. Р. 141–154. (In Russian).
• Gorozhanina E.N., Pazuhin V.N., Gorozhanin V.M., Kochetova N.N., Chibrikova E.V. (2008) Stratigraphy and lithophages of Devonian of southwestern Orenburg region (according to drilling data). Geol. collection. Ufa: IG UFRC RAS. 9, 44–53. (In Russian).
• Lyadskij P.V., Kvasnyuk L.N., Zhdanov A.V., Chechulina O.V., Shmelkov N.T., Belc G.M., Kurochkina E.S., Olenica T.V. (2013) State Geological Map of the Russian Federation. Scale 1:1 000 000 (third generation). Ural series. Sheet M-40 (Orenburg) with flap M-41. Explanatory note. St. Petersburg: VSEGEI. Р. 41 p. (In Russian).
• Fortunatova N.K., Zaitceva E.L., Bushueva M.A., Shvec-Teneta-Gurij A.G., Baranova A.V., Kononova L.I., Rahimova E.V., Miheeva A.I., Oleneva N.V., Avdeeva A.A. (2018) Unified subregional stratigraphic scheme of the Upper Devonian deposits of the Volga-Ural subregion. Explanatory note. Moscow: VNIGNI. 63 p. (In Russian).