Composition and structure of terrigenous deposits of the Givetian stage of the middle division of the Devonian system based on the results of studying the section in the zone of frontal thrust of the Urals (Gremyachinsky district of Perm Krai)

Abstract

Relevance. Industrial oil and gas potential of the Devonian terrigenous deposits of the Urals and the need to refine existing models of their formation to predict potential oil and gas deposits. Aim. To reconstruct sedimentation conditions and determine the composition of source area of the Givetian stage terrigenous rocks based on results of studying the core material of the Shirokovskaya 2 well. Object. Terrigenous rocks of the undifferentiated strata of the Vorobyov-Ardatov and Pashysky horizons of the Givetian stage of the Devonian system, penetrated by the Shirokovskaya 2 well. Methods. Lithological-facial, petrographic, X-ray fluorescence analysis, inductively coupled plasma mass spectrometry. Results and conclusions. Lithological-facies, mineralogical, petrographic, lithogeochemical studies were carried out on terrigenous deposits of the Vorobyov-Ardatov and Pashysky horizons of the Middle Devonian of the Berestyansky uplift in the area of junction of the Kosva-Chusovskaya saddle of the Pre-Ural foredeep and forward thrusts of the West Ural fold zone. It was established that the formation of the studied rocks occurred in the transitional subaquatic environments of the delta plain. A comprehensive analysis showed that the sediments of the Vorobyov-Ardatov age are sediments of the first cycle of sedimentation. The deposits of Pashysky age are lithogenic-petrogenic rocks. The composition of the petrofund mainly corresponds to igneous rocks of acidic and basic composition and metamorphic rocks. In addition, it is assumed that during the formation of rocks of the Pashysky horizon, Devonian rocks of an earlier age were also involved in sedimentation. Sedimentation during the Givetian stage took place on the passive continental margin. The supply of clastic material occurred from elevated projections of the basement and due to the erosion of Devonian deposits.

Keywords

• Vorobyevsky-Ardatov and Pashysky horizons
• Givetian stage
• mineralogy
• petrography
• geochemistry
• conditions of forming