Brachiopods as indicators of the Upper Devonian Frasnian sedimentation in the Timan-Pechora oil and gas province
Bakulina L.P., Dovjikova Y.G.
Ukhta State Technical University, Russia, Komi Republic, Ukhta, Pervomaiskaya str., 13: luda5200@bk.ru, dovzh57@yandex.ru
DOI: 10.35714/ggistrat20240100006
Summary. The paper describes faunal complexes formed in the north of the European part of
Russia under different facies conditions during the Frasnian stage of the Upper
Devonian period. The main inhabitants of the Frasnian sea basin were
cephalopods – ammonoids and bactritoids, characterized by a rich species
diversity of brachiopods, ostracods, bivalves, echinoderms, conodonts,
coniconchians and radiolarians. These complexes are somewhat similar to the Frasnian
complexes of the Russian Platform and the Western slope of the Ural Mountains.
A particularly important role in the division of the Frasnian sections played
brachiopods – inhabitants of the 30-200 m depth intervals of the warm shallow-water
basins with normal salinity. Characterized by characteristic bi-valve, bilaterally
symmetrical shells with different relief, these brachiopods are the most
important indicator of the physicochemical conditions of sedimentation. To
date, more than sixty brachiopod species with different shapes, sizes and shell
surface structures have been detected and described in the Upper Devonian
Frasnian stagsse of the Timan-Pechora oil and gas province.
Each substage, horizon and formation of the Frasnian stage is
characterized by its own set of brachiopod species distinguished for their
specific morphological features. It brings to a conclusion that the studied
rocks had been formed under different facies conditions during four major
sedimentation cycles – the Timan (Timan
formation), Khvorostan (Ustyarega formation), Semiluk (Domanik and Vetlasyan
formations) and Don (Sirachoy and Ukhta formations).
Keywords: the Frasnian
stage, the Timan-Pechora oil and gas province, facies conditions, faunal
complexes, brachiopods, sedimentation cycles
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