Devonian-Carboniferous boundary in the East of the Pechora Plate (Kamenka River and Vangyr River sections)

Abstract

The representative sections outcropping shallow-water and deep-water Devonian/Carboniferous successions in the East of Pechora Plate (Kamenka River section and Vangyr River section) are considered in respect of facies, conodont, and ostracode changes. In the Kamenka River section the D/C boundary beds are composed of bioclastic limestones interbedded with dark-gray clays (lower part of the Edzhid Fm.). The deposits contain abundant and diverse benthic ostracodes of Pseudoleperditia tuberculifera-Coryellina alba-Cribroconcha primaris ostracode Zone, and diverse conodont associations of praesulcata and sulcata zones. The negative shifts in  13 C org in conodont organic matter accompanied by weak positive shift in  13 C carb in bulk carbonates suggest eutrophic conditions in the lagoon environment and disbalancing of the trophic web at the terminal Famennian. D/C boundary beds in the Vangyr River section are represented by calciturbidites, pelagic carbonates, and shales (Izyayu Fm.). Transgressive phase of Hangenberg Event is marked by the black shale layers. The Upper Famennian conodont associations are dominated by Palmatolepis gracilis group; the ostracodes compose diverse associations of Turingian and slope ecotypes. The D/C boundary is marked by appearance of conodonts Siphonodella sulcata in associations with ostracodes Armilla uralica.

Late Devonian–early Carboniferous ostracods (Crustacea) from South China: taxonomy, diversity and implications

“…Thus, the study of ostracod assemblages from the Blue Snake section documents the increasing waterdepth from the late Famennian-Tournaisian interval, in line with the transgressive trends that have already been reported from the study of ostracod faunas from France (e.g., Lethiers & Feist 1991;Casier et al 2002), Belgium (e.g., Casier et al 2004Casier et al , 2005, Canada (e.g., Lethiers et al 1986), Urals (e.g., Zhuravlev & Sobolev 2019;Sobolev 2020) and South China (e.g., Song & Gong 2019). Blessites feluyensis, Knoxiella complanata, Praepilatina adamczalki and Bairdianella cuspis were also reported together from a succession recording a transgressive trend through the Devonian-Carboniferous transition from North Urals (Sobolev 2020).…”

“…1) from Mugodzhary, Western Kazakhstan and Sobolev (2020: figs 5, 9-10)) from Pechora Uplift, Russia, have a similar size to our material with respectively L = 532 µm, H = 250 µm and H/L = 0.47 and L = 580 µm, H = 280 µm, H/L = 0.48. However, the specimen shown in Zhuravlev & Sobolev (2019) from North Ural is slightly larger than the present material with L = 580 µm, H = 275 µm and H/L = 0.47 but still smaller than the holotype in . The size variations in our material indicate that at least two stages are present and may correspond to juveniles, compare to the holotype in , but the wide distribution of the dimensions of the specimens does not allow to clearly discriminate them.…”

“…Bairdia feliumgibba, only present in the Tournaisian in our section, were represented in lagoonal environment in the late Famennian but became extinct a little after the Hangenberg event. Blessites feluyensis, which is also only present in the Tournaisian in our section, was represented in shoal in marine open context and in transgressive trends in the Tournaisian (Zhuravlev & Sobolev 2019). This species seems to be represented in the same palaeoenvironmental settings in the Tournaisian of the Blue Snake section in South China.…”

“…Blessites feluyensis, Knoxiella complanata, Praepilatina adamczalki and Bairdianella cuspis were also reported together from a succession recording a transgressive trend through the Devonian-Carboniferous transition from North Urals (Sobolev 2020). Blessites feluyensis and Bairdia feliumgibba, were represented together in the Devonian-Carboniferous of the Vangyr River section from the east of the Pechora plate in Russia (Zhuravlev & Sobolev 2019). Bairdia feliumgibba, only present in the Tournaisian in our section, were represented in lagoonal environment in the late Famennian but became extinct a little after the Hangenberg event.…”

“…Berchogur section, Mugodzhary, Western Kazakhstan, Devonian-Carboniferous transition (Kotschetkova & Janbulatova 1987). Kamenka River section, North Urals, Russia, Famennian-Tournaisian, late Devonian-early Carboniferous (Zhuravlev & Sobolev 2019). Yjid-Kamenka river section, Pechora Uplift, Russia, Famennian-Tournaisian, late Devonian-early Carboniferous (Sobolev 2020).…”