ИСТИНА

The Dal'ny Tulkas section, which exposes the Sakmarian-Artinskian boundary interval, in the South Urals near the settlement of Krasnousolskiy, Gafuri District, Republic of Bashkortostan. It is GSSP of the Artinskian Stage ratified by IUGS in 2020 (Chernykh et al., 2023). The section represented by two complementary outcrops: the main section in the quarry wall and an additional section in a trench at its base, but GSSP is situated in main section. A study of the radiolarian assemblages from this section was performed by M.S. Afanasieva (Afanasieva et al., 2022) on material from trench only, but radiolarians occur in main section also. Study of the radiolarian assemblages from the main quarry wall becomes an urgent task. Conducting such research will not only verify the previously obtained data but also provide a more complete stratigraphic characterization of the section, thereby enabling correlation with other regions. During field studies, 19 samples were collected from the main wall of 40 m thickness. Sampling was targeted at carbonate concretion-like bodies, often lenticular, which are characterized by the most favorable conditions for the preservation and mass accumulation of radiolarian skeletons. Productive concentrations of radiolarians were identified in 9 samples. For their subsequent study and documentation, over 500 microphotographs were obtained using a scanning electron microscope. To date, the radiolarian assemblage from the wall of the Dal'ny Tulkas section comprises 37 species belonging to 18 genera. The most common are representatives of the genera Entactinia (E. parapycnoclada Nazarov et Ormiston, 1985; E. densissima Nazarov et Ormiston, 1985; E. dolichoacus Nazarov in Isakova et Nazarov, 1986), Copicyntra (C. multispinosa Kozur et Mostler, 1989; C. phymatodonta Nazarov et Ormiston, 1985), and Latentifistula (L. heteroextrema Nazarov in Isakova et Nazarov, 1986; L. turgida Ormiston et Lane, 1976; L. valdeinepta Nazarov et Ormiston, 1985). Besides them the samples contain abundant deep-water radiolarians of the order Albaillellaria, which are known for their high stratigraphic potential in the Upper Paleozoic. The investigation of albaillellarians from the Dal'ny Tulkas section provides a basis for developing a detailed zonal scheme for the Sakmarian and Artinskian stages. The established biostratigraphic framework is valuable for the precise correlation of Lower Permian strata.