SERPUKHOVIAN STAGE STRATOTYPE IN THE ZABOR'E QUARRY, PART 1: LITHOFACIES CHARACTERIZATION

Abstract

The lithofacies characterization of beds in the Serpukhovian Stage stratotype, the Zabor'e Quarry site near Serpukhov, is presented. Ten members, boundaries of which do not coincide with those of local subdivisions formerly distinguished here, are established in the section. It is shown once again that the topmost portion of Venev Horizon near the section base is karstified. Above the karstified rocks, several levels of sedimentation basin shoaling, which are marked by rhizomorphs and indications of fresh-water diagenesis, are recognized. The first level crowns the lower third of the Tarusa Horizon, the second one is in the upper part of the latter and considered to be its upper boundary, and the third level in the upper third of the lover Steshev Subformation may characterize two nearby events of shoaling. Parallel to aridity indications enhancing upward in the Zabor'e and Novogurovskii sections, rocks of that subtidal reveal storm-born marks in subtidal facies. As is established for the first time for the Okaian-Serpukhovian interval, the high-energy grainstones and intertidal laminites with storm-born marks appear in the terminal part of the lower Steshev sequence. Thus, the transition from the humid climate of the Okaian-Tarusa time to the more arid climate of the Steshev time could be accompanied by enhanced movements of air masses that triggered development of storm sedimentation. The last conclusion needs however to be verified in other sections of the study region.