Palynology of the upper Barremian and lower Aptian interval in parts of North Bulgaria

Upper Barremian and lower Aptian dinoflagellate cyst assemblages have been documented for the first time from five ammonite-controlled sections in Central and Northeast Bulgaria. They include important biostratigraphical markers, such as Rhynchodiniopsis aptiana, Prolixosphaeridium parvispinum, Cerbia tabulata, Lithodinia stoveri and Ctenidodinium elegantulum. The distribution of taxa is generally consistent with published palynostratigraphical schemes, but some differences are noted in this study. The best global markers for the lowermost Aptian interval are represented by the LOs of R. aptiana and C. elegantulum; however, in the sections studied, these taxa consistently occur only within the upper Barremian. The recorded overwhelming dominance of the Classopollis group, together with persistent records of pteridophyte spores, is interpreted as indicative of extremely hot and humid climate, which caused and accompanied the deposition of the OAE 1a in this part of the Tethyan Realm.