Geologicheskii Vestnik

Ordovician deposits of the western slope of the Southern Urals are known in three structural-formational zones: West Zilair, East Zilair and in the Uraltau zone. In recent years, new data on paleontological dating have been accumulated and changes have been made to the age of regional stratigraphic units. The greatest changes affected the Uraltau zone, where the formations of the Suwanyak complex, pre viously attributed to the Precambrian, were given Ordovician and Silurian ages on geological maps at a scale of 1:200 000. Ichnofossils from Ordovician deposits on the western slope of the Southern Urals are described for the first time. Pronounced ichnocomplexes have been established that belong to two ichnofacies: deep-sea nereite and coastal scolitic. The nereite ichnofacies is represented by the ichnofossils Bergaueria isp., Cosmorhaphe isp., Helminthopsis isp., Megagrapton isp., the scolitic ichnofacies – Skolithos linearis Haldeman, Roziella isp., Bergaueria isp., Planolites isp. The West Zilairian part of the section was formed under the conditions of the scolitic ichnofacies, in the conditions of a shallow shelf. East Zilair and Uraltau zones — in deep-water environments at the foot of the continental slope in conditions of the nereite ichnofacies. The results obtained are in good agreement with paleontological, geochemical and sedimentological data and make it possible to use ichnofossils to make paleofacies constructions.

Ordovician, sedimentary environments, ichnofossils, Southern Urals

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