PALEOECOSYSTEM OF DORSOPLANITES PANDERI PHASE IN THE VOLGA SHALE-GENERATING BASIN

Abstract

The ecosystem of the formation period of low-calorie oil shales and sapropel clays at the final Dorsoplanites panderi phase of the basin evolution was examined. Paleobionomic reconstructions were made on the basis of investigations of fauna remains, and the analysis of the rock composition, fabrics, structures, and nannostructures, kerogen composition and properties, pelitic components, and other specific features that revealed the leading role of coccophore skeletal and organic remains in the composition of primary sediments. Sedimentation occurred under conditions of unstable salinity and a hydrodynamic regime within shallow (80-100 m maximum) and temperately warm waters. Reactions in the sediments of the shallowing basin altered from reducing to slightly oxidizing. Periodic breaks in anoxic environments within sediments, which were transformed into combustible shales with low heating efficiency, caused substantial degradation of the primary organic matter.