Triassic lithostratigraphic correlation in the Moesian Platform (Bulgaria-Romania)

The Moesian Platform occupies a wide area in Bulgaria and Romania, being surrounded to the north and west by the South Carpathians and to the south by the Balkans. The lithostratigraphic division of the representative cross-sections of the Triassic system is performed for both countries. The applied methodology in defining the lithostratigraphic units and their comparison is based on the internationally accepted, widely used stratigraphic rules. The key role of the present work is to unify positions and technical usage of the Triassic lithostratigraphic units. However, they are relatively different in Bulgaria and Romania, which hampers the cross correlation. The Bulgarian part of the Moesian Platform is examined according to the “Regional Lithostratigraphic Scheme of the Triassic sediments from borehole sections in North Bulgaria” compiled by Chemberski in 1985. The lithostratigraphic division for the Romanian part is based on Paraschiv’s work completed in early 1980s. There are three Triassic complexes defined in the Moesian Platform which are divided into formations and horizons. They follow in order of deposition: Lower red bed complex represented by Petrohan Group (Bulgaria) and Rosiori Formation (Romania); Carbonate complex including Iskar Carbonate Group (Bulgaria) and Alexandria Formation and Putinei evaporates (Romania); Upper variegated complex consisting of Moesian Group (Bulgaria) and Segarcea Formation (Romania). The present correlation determines three types of comparative units: analogous units (subjective synonyms); units defined in Bulgarian territory and probably present also in Romania; units located only in the Bulgarian and respectively in the Romanian part of the Moesian Platform.