Lithological and biostratigraphic characteristics of the Upper Silurian and Lower Devonian deposits of the southwestern part of the field named after Roman Trebs

Abstract

A conodont sequence from the Przhidolian stage of the Upper Silurian and almost the entire Lokhkovian stage of the Lower Devonian has been established in the sections of the Upper Silurian-Lower Devonian on the southwestern part of the field named after Roman Trebs (Timano-Pechora oil and gas province). According to the conodonts, two biostratigraphic subdivisions are distinguished in the rank of layers with fauna in the Upper Silurian and three of them in the Lokhkovian stage of the Lower Devonian. The layers can be compared with the standard conodont zonal scale. The Silurian-Devonian boundary has a complex rationale for biostratigraphic data (conodonts), cyclostratigraphy, and logging data (electrical and radioactive methods). The Lower Devonian deposits are overlain by terrigenous packs of the Timanian horizon of the Frasnian stage. The break in the sedimentation covers the interval from the Praghian stage of the Lower Devonian to the Dzhierskian horizon of the Frasnian stage of the Upper Devonian inclusively. The regularity of the placement of reservoir rocks in the section of wells is analyzed and their relation to the cyclicity of sedimentation is noted.

Keywords

• Silurian
• Devonian
• conodonts
• logging
• lithology
• cyclicity