Abstract

Devonian deposits of the western slope of the Urals are represented chiefly by clastic-carbonate, reef and shale complexes.

The clastic-carbonate facies (D₂¹₂ - C₁t) exposed in anticlinoria of the south, middle, north, and polar Urals is characterized by distinct cyclic recurrence. Each cycle is formed by a regular succession of clastic, clay-carbonate (in some cases Dominik), carbonate and bioherm lithofacies, in ascending order. The clastic facies includes minerals of economic value.

The reef facies (D₁ - D₂¹₁) is locally developed in the Urals. Cyclic recurrence typical for the clastic-carbonate facies, has not been observed in these deposits. They are represented by massive carbonates of organic framework with a biohermal reef-nucleus, by clastic carbonates formed on the reef flanks, and by lagoonal deposits of impure carbonates. In laminated rocks, the faunistic complexes of reef formation are isolated from coetaneous biocoenoses by local spreading and by weak variability in time.

The slate formation (D₃ - C₁t) is known in a synclinal structure of the western and eastern slopes of the Urals. The microrhythm is typical. In the deposits the original mineral zonation of the products of erosion of basic and ultrabasic rocks is established.

The Devonian formations of the miogeosynclinal zone of the Urals are confined to the definite structural formational zones of the old basement. The palaeostructural control is the main reason for the spatial separation of these formations.