Infrazonal subdivision of the Volgian Stage in its type area by ammonites and its Panboreal correlationкод для вставки
Infrazonal subdivision of the Volgian Stage in its type area by ammonites and its Panboreal correlation Rogov M.A. Russia, Mosсow, Geological Institute of RAS Volgian stage Since the beginning of study of the latest Jurassic of the european part of Russia its succession could not be directly correlated with those of the Western Europe Ammonites virgatus Buch Ammonites catenulatus Fischer The Volgian Stage has been proposed by S.N. Nikitin (1881, published in Russian and German) for the uppermost part of the Jurassic System: “für die ganze Masse jurassischer Schichten in Mittelrussland, die über dem Oxfordthon liegen, ebenfalls eine besondere Benennung “Wolgaformation” einzuführen” Threefold subdivision of the Volgian Stage has been established since 60th years of the XX century and used for the whole Arctic Most important features of biohorizons are: • • • - potential indivisibility to those taxonomic criteria on which they are established; - determinacy of the both lower and upper boundary of biohorizons in a geological section; - identification from recognition of the single (unique) index-taxon (usually species or subspecies) Infrazonal scales are based on combination of phylogenetic and immigrational bioevents Gorodischi section Murzicy section Lower Volgian Substage Lower Volgian Substage Ilowaiskya – “Pseudovirgatites” succession Lower Volgian Substage Paralingulaticeras efimovi Neochetoceras spp. Lower Volgian Substage Schaireria neoburgense Franconites cf. vimineus Lower Volgian Substage Presence of some Submediterranean taxa in the Volgian Stage of the Russian Platform permits the possibility of direct correlation of the Lower Volgian with Tithonian succession Lower Volgian Substage Correlation chart of the beds around the Kimmeridgian–Volgian boundary and its equivalents through Europe (Rogov, Price, 2010) Middle Volgian Substage Eganovo section Gorodischi section Middle Volgian outcrops Middle Volgian Substage Zaraiskites Middle Volgian Substage Virgatites Middle Volgian Substage Epivirgatites and Laugeites Upper Volgian Substage Ammonites in the Eganovo section Milkovo section Eganovo section, Moscow area Upper Volgian Substage Kachpurites lineage Upper Volgian Substage Garniericeras, Craspedites (Trautscholdiceras) and Volgidiscus Comparative completeness of the selected Middle-Upper Volgian sections Laugeites spp. Nordvik, N. Siberia Craspedites praeokensis - okensis Nordvik European Russia N. Siberia European Russia Volgidiscus Craspedites (Taimyroceras) Nordvik, N. Siberia Panboreal correlation of the Volgian Stage Thanks for your attention!