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Union of Soviet Socialist Republics
Devonian of the Timan-Pechora Region
In the territory of the Timan-Pechora region the Devonian deposits are represented by essentially the same sedimentary types as are known in the region of the Russian platform, namely those of the northwestern central and eastern districts. The rich and complex fauna developed in the Timan-Pechora region corresponds pimarily with the eastern type of the platform.
In the Timan-Pechora region the successive transition of all main types of Devonian of the Russian platform is observed. Such a distribution of the Devonian sediments may be explained by the nearness of the Baltic shield to the Ural geosyncline, and by the step-by-step subsidence of the platform toward the geosyncline.
The structural-facies zones are clearly distinguished, being arranged parallel to the Urals and Crossing the Timan ridge meridionally. In some cases chains of islands appear along the margins of the respective transgressions. These islands separate structural-facies zones not only by the character of the sediments but also by the composition of the faunas. The intensive sagging in the Devonian at the site of the existing Pechora ridge (zones of contact between two distinct basement types) was compensated by increased accumulation of sediments having a thickness up to 3500 metres. On the other hand, the gradual subsidence of the sea bottom, as a consequence of block subsidence of the basement, gave rise to the formation of sedimentationally uncompensated basins of Domanik type. They were forced back toward the Ural geosyncline, where, as a result of Variscian tectogenesis, the pre-Ural foredeep developed on the site of the last, U-shaped Famennian basin.
The Devonian deposits of the Timan-Pechora basin are rich in oil and gas. The hydrocarbons accumulated in sand reservoirs at the base of the transgressive series of the Middle and Upper Devonian, and also in Famennian carbonate reservoirs. Oil and gas fields are known only in the deposits of eastern subregion type.
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