The Shirokoe Place as a reference section of the upper Visean substage in the Upper Pechora basin (Unya river, Northern Urals)

Abstract

Research subject. Carbonate rocks in the “Shirokoe Place” section (Unya River, Northern Urals). Material and methods. The work was based on a study of the composition and structural peculiarities of rocks and species diversities of forami- nifera and calcareous algae in the most important section of Upper Visean sediments in the lower reaches of the Unya river.Results. The rocks in the section are represented by bioclastic limestones, dolomites and various transition differences. The section features a wide presence of green Koninckopora, red Epistacheoides and Ungdarella algae. Less common are Palaeoberesella, Anthracoporella, Kamaena and Stacheoides. Fasciella is extremely rare, and Calcifolium is virtually absent. Foraminifera complexes are representative, but there are no zonal species Eostaffella tenebrosa (Venevsky horizon), genera Valvulinella (Tula horizon), Bradyina and Howchinia (Mikhailovsky and Venevsky horizons). Endothyranopsis, Janischewskina and Cribrospira are rare.Conclusions. The study of the species diversity of foraminifera and calcareous algae allowed us to clarify the stratigraphic division of the upper Visean sediments in the “Shirokoe Place” section. The Tula, Aleksinsky, Mikhailovsky and Venevsky horizons of the Upper Visean were reliably identified. The studied section can be used as a reference when creating stratigraphic schemes of Later Visean deposits for the Western subzone of the Upper Pechora transverse sinking of the Western folded zone of the Urals and adjacent areas of the PreUrals regional trough.