Geologicheskii Vestnik

The article presents а material on the study of a fragment of Vendian Basa Formation sedimentary rock section exposed by excavation during road construction in the Makarovo – Kulgunino part. Comparison with the reference sections of the Basa Formation along the Zigan River and Kukrauk stream (Southern Urals) showed that the studied fragment corresponds to the upper (sandstone-siltstone) sequence, based on the lithological composition of rocks and lateral distribution. The section fragment at the Makarovo – Kulgunino road area is distinguished by the presence of ash tuff interlayers, which are very rare in natural outcrops, so it gives it a special status. Based on the zircons extracted from the tuff by the U-Pb SHRIMP II method, the age of the Formation and the Timan orogeny is reliably determined, which signi cantly completes the characteristics of the stratotypic sections of the folded complex rocks of the Asha series in the territory of “Toratau” geopark. This fragment of the section may become an interesting geological object for geologists and tourists.

Basa Formation, Vendian, tuff, geopark, Southern Urals

• Grazhdankin D.V., Marusin V.V., Meert Dzh., Krupenin M.T., Maslov A.V. (2011) The Kotlinsky horizon in the Southern Ural. Dokl. Earth Sciences, 440(2), 201-206. (In Russian).
• Kozlov V.I. (1982) Verkhnii rifei i vend Yuzhnogo Urala [Upper Riphean and Vendian of the Southern Urals]. Moscow, Nauka Publ., 128 p. (In Russian).
• Puchkov V.N. (2010) Geologiya Urala i Priural’ya (aktual’nye voprosy stratigrafi i, tektoniki, geodinamiki i metallogenii) [Geology of Urals and Cisuralian area (topical issues of stratigraphy, tectonics, geodynamics, and metallongeny)]. Ufa, DesignPoligraphService Publ., 280 p. (In Russian).
• Razumovsky A.A., Novikov I.A., Ryazantsev A.V., Rudko S.V., Kuznetsov N.B., Yashunsky Yu.V. (2020) Ancient Vendian fossils of Eurasia: U-PB isotopic age of the Basa Formation (Asha series, Southern Urals). Dokl. Earth Sciences, 495(2), 3-8. (In Russian).
• Sergeeva N.D., Puchkov V.N., Krasnobaev A.A., Kozlova O.V., Ratov A.A. (2019) Asha Series of Vendian: an orogenic complex of Timanides in the Southern Urals. Geologicheskiy vestnik – Geological Bulletin, (1), 3-34. DOI: 10.31084/2619-0087-2019-1-1. (In Russian).
• Sinicyn I.I., Sinicyna Z.A. (1965) Geologicheskaja karta SSSR. Serija Juzhno-Ural’skaja. M 1:200 000. List N-40-XXI [Geological map of the USSR. South Ural series. Scale 1:200 000. Sheet N-40-XXI]. Moscow, GUGK Gosgeolkom of USSR. (In Russian).