Investigating the changes of allochems and calcareous nannofossils in Kazhdumi Formation: possible consequences of fault activity

The current research was conducted with the aim of investigating environmental changes based on calcareous nannofossils. For this purpose, a section of the Kazhdumi Formation was sampled southwest of Yasouj. As a result of the study of 60 smear slides, 42 species belonging to 21 genera of calcareous nannofossils were identified from marine deposits. According to the recorded nannofossils, the age of Albian for Kazhdumi Formation in the studied section was determined. In addition, this study led to the establishment and differentiation of the following bio-zones: Prediscosphaera columnata Zone and Eiffelithus turriseiffelii Zone. Also, the evaluation of facies in the present study shows rapid sea-level changes. On the other hand, it seems that the activity of the Kazerun fault has caused changes in the sedimentary conditions and the creation of different facies during the Albian stage. Therefore, fossil data together with lithostratigraphic studies indicate sedimentary changes from a shallow carbonate system to deep marine sediments.