Abstract <p>As a result of lithofacies studies and analysis of geological data available, Riphean–Vendian boundary deposits from different regions of the Southern Urals (Tolparovo, Krivaya Luka, and Tirlyansky) were correlated. In the first two regions, a lithological marker of glacial-diamictite deposits with vertical change of terrigenous facies has been established, from shallow-sea tidal sediments with signs of superposition of marinoglacial sedimentation to deeper ones corresponding to the conditions of underwater delta-type outflow cones or fjords. Owing to the strong tectonization and metamorphism of the Riphean–Vendian deposits, the sequence of formations in the Tirlyansky region considered as the Arshinian series is ambiguous and their correlation with other areas is difficult. We propose a new interpretation of the position of the Arshinian series formations. The series is based on volcanics of the Igonino Formation, reflecting the stage of rifting. Higher in the section, there are sandy-clay deposits of the Bainas formation (and its inferred facies analog, the Shum Formation), accumulated in mobile shallow water environment. These deposits are correlated with those which underly diamictites in the Tolparovo and Krivaya Luka regions. The upper part of the section is represented by glacial diamictite conglomerates of the Makhmutovo Formation. Under this interpretation of the position of the Arshinian series formations, a single Riphean–Vendian boundary marinoglacial level can be traced throughout the Bashkir meganticlinorium in its western and eastern frames. Therefore, it can be included in the Upper Precambrian stratigraphic scale of the Southern Urals.</p>