Comparative characteristic of the Ufimian sandstones in the Solikamsk basin

The results of study of sands rocks of the Ufimian Stage in the wells cross-sections of the Solikamsk depression allowed determining evolution of their composition expressed in the change from predominantly oligomictic quartz partially with fragments of rock to polymictic greywacke presented mostly by the fragments of volcanic rock. This change may be resulted from successive erosion from external to internal zone of the Uralian orogen or shifting the base level of erosion eastward. Facial analysis of rock allowed identifying that the sedimentation initially occurred in the lagoon conditions following the shallow-water and deltaic (Solikamsk time), and continental lake and river (Sheshminskiy time) conditions. The obtained results allowed restoring paleogeographic and tectonic conditions of sedimentation. In the latitudinal section of the Solikamskaya depression, a regular variation of sand material from the east (Uralian orogenic belt) to the sea basin (westward) was revealed, and the deposits were associated with channel and fan deltaic facies. Overlying continental lacustrine, alluvial, and proluvial sediments, are widely developed only at the southwestern part of the basin.