Serpukhovian Stage (Carboniferous) in type area: Sedimentology, mineralogy, geochemistry, and section correlation

This paper delivers bed by bed descriptions and detailed correlation of the sections Novogurovskii, Dashkovka, and Zaborie of the type area of Serpukhovian Stage of the International Stratigraphic Chart. Above a weakly expressed Forino Unconformity discovered in the lower Tarussian, no subaerial unconcormities can be confirmed up to the top of Steshevian. The basinal character of the Steshevian lobata montmorillonite shale unit is demonstrated. Oxygen minimum and perhaps greatest Early Serpukhovian highstand is revealed by geochemistry and trace fossil association in the lower part of the lobata shale. The paleogeographic model of the “Steshevian basin” outlined in this paper involves suppression of photozoan carbonate production in front of a lowenergy delta causing development of a shallow depression in the surrounding carbonate platform. In the Steshevian black shale unit, upward change from lobata montmorillonites to shallower marine palygorskites is explained by evaporative pumping of magnesium and silica in basinal water under progressive climatic aridization.