SIGNIFICANCE OF MICROFOSSILS FOR RIPHEAN STRATIGRAPHY OF THE SOUTHERN URALS (BASHKIRIAN MEGANTICLINORIUM) AND ADJACENT REGION (KAMA-BELAYA AULACOGEN)

Abstract

Taxonomic composition of six stratigraphically important Riphean microbiotas from the southern Urals (Bashkirian meganticlinorium) and adjacent region (the Verkhnyaya Kama depression of the Kama-Belaya aulacogen) is considered. Microbiotas characterize the Kuzha (two microbiotas), Tyul'men, Nugush, and Lemeza sequences of the Riphean stratotype and the Kyrpy Group (Pal'niki microbiota) of the eastern Russian plate. Stratigraphic interpretation of these deposits (except the Nugush and Lemeza sequences) is still ambiguous. The Kuzha and Tyul'men sequences are considered either as diachronous and belonging to different horizons of the upper part of the Middle Riphean Yurmatinian Group, or as synchronous and corresponding to the long-lasting pre-Karatavian hiatus. The Kyrpy Group of the Urals region is referred to the Lower Riphean, although some researchers correlate it with the Karatavian. The examined microbiotas (first of all, the Kyrpy and Nugush ones) consist of abundant and diverse (more than 20 genera and 25 species) microfossils including those of the intricate structure. The new data obtained elucidate the structure of the Yurmatinian-Karatavian interval of the Riphean and the age of the Kyrpy Group of the Urals region, being useful for the distant interregional correlation.