Due to the importance of calcareous nannoplanklon hiostratigraphy in Mesozoic and Cenozoic strata, the Abtalkh Formation was studied at the chachaheh section (kalat-Mashhad Road ), This section is located in kopeht — Dagh area and comprises of grey. grey bluish marl and shale
The Abtalkh Formation rests comformably on Abderaz Formatona and it is underlain by Nizar Formation corn formably.
For the first time the calcareous nannofossil of this formation were studied.As a result of this study 50 species, 20 genera and 12 families were determined and illustrated.
Based on the obtained nannofossils, the sample interval is consistant with CC 18 , CC22 of sissingh (1979 ) Zonation, for the Lower part, and tipper part of Abtalkh formation Therefore the age of this formation in studied area is suggested Early- Late campanian