Devonian-Carboniferous boundary beds in the Vorkuta transverse uplift (Bolshaya Usa River)

Abstract

The paper contains multidisciplinary data on the lithology and palaeontology of the Devonian–Carboniferous boundary beds in the shallow-water facies in the Bolshaya Usa River section (Vorkuta Uplift). A recent discussion on the position and marker of the Devonian–Carboniferous GSSP shows that this study is highly relevant. In the Bolshaya Usa River section, the boundary almost coincides with the boundary of the Bakhromchataya Fm. and Vazhkhanovey Fm. The upper part of the Famennian (upper part of the Bakhromchataya Fm.), which is mainly composed of microbial, algal, and bioclastic carbonates (wackestone), contains poor conodont and foraminifer associations. Prioniodinida dominates the conodont associations. Foraminifers are mainly represented by unilocular forms accompanied by the rare Eoendothyra and Quasiendothyra. The lower part of the Tournaisian (basal beds of the Vazhkhanovey Fm.) is composed of clastic carbonates containing numerous brachiopod shells (Spinocarinifera). Conodont associations are represented by Prioniodinida of wide stratigraphic range, as well as by Pseudopolygnathus primus Branson et Mehl and Patrognathus crassus Kononova et Migdisova. Foraminifers are represented by just unilocular forms, namely: Parathuraminites, Parathuramina, Bisphaera, Vicinisphaera, and Earlandia. The position of the Devonian-Carboniferous boundary in the study section is defined by the first occurrence of conodonts Patrognathus crassus, Pseudopolygnathus cf. primus and foraminifers Earlandia cf. minima and E. elegans. These taxa can be considered as markers of the boundary in shallow-water facies of the carbonate platform.

Keywords

• conodonts
• foraminifers
• biostratigraphy
• devonian/carboniferous boundary
• polar urals