Biostratigraphy of the Devonian–Lower Carboniferous Deposits of the Bambui-Olingda Subzone (South Muya Ridge, Western Transbaikalia)

Abstract

The results of biostratigraphic studies of the Devonian–lower Carboniferous deposits of the Bambui-Olingda subzone of the Vitimkan-Tsipinsk zone of the Baikal-Vitim fold system are presented. These deposits are isolated from the composition of the Riphean and Vendian–Cambrian formations. Their age was revised on the basis of numerous findings of fauna and flora. The carbonate Bambui and terrigenous Chulegma formations and the terrigenous-carbonate Kadalin stratum are assigned to the Devonian. The volcanogenic-terrigenous Yendekt sequence is dated as late Devonian (Famennian)–early Carboniferous (Tournaisian), while the terrigenous Ognenskaya and Amatkanskaya formations are dated as early Carboniferous (Tournaisian and Visean). Significant changes have been made to the Paleozoic stratigraphy scheme of the subzone. Paleolandscape reconstructions for the Bambui-Olingda basin and coastal land areas in the Devonian–early Carboniferous are proposed. The Devonian carbonate complex was formed in calm conditions of a shallow warm shelf sea. A change in the paleolandscape situation occurred at the Devonian–Carboniferous boundary. Sedimentation of significant thicknesses continued under the conditions of a deepening open shelf-slope paleobasin adjacent to the volcanic zone.