Sergey Vladimirovich Naugolnykh

The paper focuses on the preliminary description of the paleosol profile (microprofile) of Late Proterozoic (Vendian) age. The profile was found on the left bank of the Kosva River downstream of the Shirokovskoe water reservoir (Gubakha District of the Perm region). The upper part of this profile (genetic horizons of B and BC) is dissected by vertical tracks of desiccation. The lower part of the profile (siltstone of the horizon C) contains fossils of soft-bodied metazoan organisms including pinnate forms (Petalonamae), bilateral movable benthic forms (Proarticulata), medusoids and cyano-bacterial films. A model of organization of the studied facial and paleoecological loci is proposed. The paleosuccession is reconstructed on the basis of the sections studied and discussed. The matrix containing the paleosol profile formed in conditions of near-coast shallow-water basin. The siltstones of the matrix with the lumpy structure and small spherical concretions were exposed in aerial conditions, what influenced on structure of initial sediment from stratificated layer to lumpy soil matrix in a result of vertical cracking of the initial sandy-clayey matrix. After that, the conditions of shallow-water marine or lagoon basin came back, and the biota of soft-bodied organisms had developed there. Then, after shallowing of the basin, the deposited sediments exposed in aerial conditions again, perhaps in zone of wave dropping near the littoral. Presence of water let the bacterial-algal community to develop. Atmospheric agents together with insolation led to cracking of upper surface of the forming soil microprofile FPS-Sh1.