Correlation of the Triassic rocks in the Moesian platform (Bulgaria-Romania)

The Moesian platform occupies a large area in Bulgaria and Romania. A lithostratigraphic division of the cross-section of the Triassic system is performed for both countries. The applied methodology in defining the lithostratigraphic units is based on the “International stratigraphic Guide” by Hedberg. Although the present work aims to unify positions and technical usage of the lithostratigraphic units the latter are rather different in Bulgaria and Romania, which makes difficult the cross correlation.
   The Bulgarian part of the Moesian platform is examined according “Regional lithostratigraphic scheme of the Triassic sediments on borehole sections in North Bulgaria”.
   The lithostratigraphic division for the Romanian part is based on publications. The following lithostratigraphic units are determined in the Moesian platform:
   In the Lower red colour complex: Bulgaria - Petrohan Group and Red colour sandstone unit, Stejerovo Fm., Alexandrovo Fm. and Dobrudja Fm.; Romania - Vedea-Jiu Group (Carboniferous-Permian-Scythian), Rosiori Fm. (Permian-Scythian) and horizons Bradesti and Viisoara;
   In the Carbonate complex: Bulgaria – Iskar Group, Doirentsi Fm., Mitrovtsi Fm., Russinovdel Fm., Preslav Fm. and Tulenovo Fm.; Romania - Alexandria Fm. (Permian-Scythian-Anisian), Putinei evaporites.
   In the Upper variegated colour complex: Bulgaria - Moesian Group, Kozlodui Fm., Komshtitsa Fm., Gorni Dabnik Fm., Tuchenitsa Fm., Dulovo Fm., Kaliakra Fm. and Shabla Fm.; Romania - Oltet Group (Triassic-Lias-Dogger), Segarcea Fm., horizons Curmatura, Beiu and Teascu, Motoci complex.
   The present correlation determines three type of units: A) Analogous units (subjective synonyms); B) Units defined on Bulgarian territory and probably present also in Romania; C) Units located only in Bulgarian and respectively in Romanian part of the Moesian platform.
   The detailed research and well investigations demonstrate the following results:
   A) Analogous units (subjective synonyms):
   In the Lower red colour complex there are Red colour sandstone unit (Bulgaria) – Bradesti horizon (Romania); Stejerovo Fm. (Bulgaria) – Viisoara hor. (Romania); Petrohan Group (Bulgaria) – Triassic part of the Rosiori Fm. (Romania, Permian-Triassic) and Vedea- Jiu Group (Romania, Carboniferous-Permian-Scythian).
   In the Carbonate complex have been established Doirentsi Fm. (Bulgaria) – Anisian parts of the Alexandria Fm. (Romania, Permian-Scythian-Anisian).
   In the Upper variegated colour complex there are Komshtitsa Fm. (Bulgaria) – Curmatura hor. (Romania); Gorni Dabnik Fm. (Bulgaria) – Beiu hor. (Romania); Dulovo Fm.(Bulgaria) – Teascu hor. (Romania); Moesian Group (Bulgaria) - Segarcea Fm. (Romania) and Triassic part of the Oltet Group (Romania, Triassic-Lias-Dogger).
   B) Units defined in Bulgaria and probably developed also in Romania:
   In the Lower red colour complex there is Alexandrovo Fm.
   In the Carbonate complex there are Mitrovtsi Fm., Russinovdel Fm., Preslav Fm. and Iskar Group.
   In the Upper variegated colour complex there is Kozlodui Fm.
   C) Units characteristic only of Bulgaria, respectively only of Romania:
   In the Lower red colour complex have been established Dobrudja Fm. (Bulgaria), Scythian carbonates (Romania, part of the Alexandria Fm.).
   In the Carbonate complex there are distinguished Tulenovo Fm. (Bulgaria), evaporites from Putinei (Romania).
   In the Upper variegated colour complex there are Tuchenitsa Fm. (Bulgaria), Kaliakra Fm. (Bulgaria), Shabla Fm. (Bulgaria), Motoci complex (Romania, sedimentaryvolcanogenic).