nannostratigraphy of boundary of tirgan and sarcheshmeh formations at qalezo section in the west of kopet-dagh basin

calcareous nannofossils in boundary of tirgan and sarcheshmeh formations at qalezo section have been studied. this section is situated in the west of kopet-dagh basin. in this study 35 nannoplankton species of 17 genera were identified. according to the first occurrence of index species and fossil assemblages two calcareous nannofossil biozones (cc7-cc8) of sissingh (1997) have been recognized. based on these biozones, age of this boundary is late aptian - early albian.