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The Oxfordian Stage of West Siberia contains Boreal ammonites Cardioceratidae. The authors’ bank of paleontological data includes ~ 500 definitions of Cardioceratinae, permitting a considerable refinement of the official Oxfordian regional zonal scale. The lower substage is divided into the Cardioceras (Scarburgiceras) obliteratum, C. (S.) scarburgense, and C. (S.) gloriosum Zones instead of beds with C. (S.) spp., whereas the C. (Cardioceras) percaelatum and C. (C.) cordatum Zones are recognized instead of beds with C. (C.) spp. We have found new ammonites typical of the Middle Oxfordian C. (Subvertebriceras) densiplicatum and C. (Miticardioceras) tenuiserratum Zones. The first of these zones is divided into two subzones. The Upper Oxfordian includes the Amoeboceras glosense and A. serratum Zones instead of beds with A. spp., and the A. regulare Zone and beds with A. rosenkrantzi are recognized instead of the A. ex gr. regulare Zone. The genus Ringsteadia (Aulacostephanidae) is observed only in the northwestern part of the region, along the eastern slope of the North Urals; therefore, two upper units of the biostratigraphic scale correspond to beds with Ringsteadia marstonensis. In the Oxfordian, West Siberia and northern Siberia belonged to the North Siberian province of the Arctic realm. Only in the latest Oxfordian did the northwestern West Siberian basin become part of the Boreal–Atlantic realm, as evidenced by the distribution of Ringsteadia on the eastern slope of the Cis-Polar Urals.

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On the basis of the results of studying the faunal collections of bivalves and foraminifera collected in the period of 1976-2014 in the Cape Tsvetkov region in Eastern Taimyr, the knowledge of the Pliensbachian-Aalenian part of the section of the Tsvetkov geological region is expanded. The bedding in the section is described, and a comprehensive paleontological characteristic is given. For the first time for this section, the following taxa are included in the composition of characteristic bivalve assemblages: Praemeleagrinella deleta, Siungiudella cf. parvula, Mytiloceramus (Lenoceramus) vilujensis, Mytiloceramus (Pseudomytiloides) oviformis, Oxytoma ex gr. kirinae, Arctotis (Praearctotis) similis, and Arctotis (Arctotis) tabagensis. On the basis of the use of auxiliary biostratigraphic subdivisions-beds with bivalves and F-zones based on foraminifera-the section is correlated with the standard boreal ammonite scale. The age of the local stratigraphic units of the Eastern Taimyr structural-facies zone is refined. The Kiterbyutskaya Formation is considered within the Tiltoniceras antiquum-Dactylioceras commune zones, the Korotkinskaya Formation is considered within the Dactylioceras commune-Pseudolioceras falcodiscus zones, and the Aprelevskaya Formation is considered within the Pseudolioceras maclintocki Zone. For the first time, images of the leading species of bivalves are presented.