BASHKIRIAN-MOSCOVIAN BOUNDARY BEDS IN SOUTHERN TURKEY: FORAMINIFERAL BIOSTRATIGRAPHY AND SEQUENCE STRATIGRAPHY
The Bashkirian portion of the sections has been divided into five zones, namely Pseudostaffella praegorskyi-Profusulinella staffellaeformis Zone (Askynbashkyi), Pseudostaffella gorskyi-Eoschubertella obscura Zone (lower Tashastinskyi), Ozawainella pararhomboidalis Zone (upper Tashastinskyi) and the upper two, Pseudostaffella subquadrata-Profusulinella tashliensis Zone and the Profusulinella praeprisca Zone belonging to the horizon Asatausky. The lower Moscovian (Solontovsky) is characterized by the Profusulinella prisca-Aljutovella aljutovicaZone.
The Bashkirian-Moscovian boundary is delineated by the first occurrence of Profusulinella prisca, one of the end members of the P. staffellaeformis-P. paratimanica lineage. This level also coincides with the first occurrence of Aljutovella aljutovica. The datum corresponding to the first occurrence of the genus Eofusulinais slightly higher than those of the zonal markers of the base Moscovian.
Stacking patterns of upward-shoaling meter-scale cycles in the measured sections indicate the presence of two third-order sequences dated as Askynbashky to lowermost Asatusky and Asatausky to Solontovsky. The prominent quartz arenitic level intercalated within the Upper Bashkirian carbonate succession has been interpreted as a falling stage systems tract corresponding to stratal offlap during the culmination phase of the second glacial interval in the Carboniferous. Following the sea-level fall in the earliest Asatausky, a new carbonate regime was installed in the Asatausky-Solontovsky interval by a glacio-eustatic sea-level rise. The Bashkirian-Moscovian boundary seems to be located within the transgressive systems tract of this new carbonate regime.