Revision of ammonoid biostratigraphy in the Frasnian (Upper Devonian) of the Southern Timan (Northeast Russian Platform)

New field work in outcrops of the Ukhta Region (Southern Timan) together with the re-exanimation of former collections allows a detailed revision of the ammonoid zonation in one of the classical Frasnian regions of Russia. There is a total of 47 species, 18 of which are new or recorded for the first time from the region. The latter applies to representatives of Linguatornoceras, Phoenixites, Aulatornoceras s.str. and Acanthoclymenia. New taxa are Chutoceras manticoides n. gen. n. sp. and Linguatornoceras yudinae n. sp. In the Ust'yarega Formation regional Hoeninghausia nalivkini, Timanites keyserlingi and Komioceras stuckenbergi Zones can be recognized which correlate with the international Frasnian divisions UD I-B/C. The Ponticeras domanicense Zone (UD I-E)occupies most of the Lower Domanik, the Nordiceras timanicum Zone (UD I-F to I-H) is developed in the Middle and Upper Domanik. Following a poorly defined and short interval which rare Carinoceras, pelagic sequences of the Lyaiol Formation (Members 2-4) fall in the Virginoceras ljaschenkoae and Manticoceras lyaiolense Zones (UD I-I/J). Late Frasnian deposits (UD I-K/L) have not yielded any ammonoids so far. Correlation betwen the new zonation and the conodont zonation (Montagne Noire zones) is provided.