Biostratigraphy of the Qom formation deposits based on calcareous nannofossils in the South east Kashan

In this study, the sediments of Qom Formation were investigated in South East of Kashan. This Formation with a thickness of about 339 m consists of marl, limestone and marly limestone that disconformity lie between Lower Red Formation and conglomerate of Pliocene at the top. The study of 113 samples taken from the section led to the identification of 34 species and12 genera of calcareous nannofossils. In this study were used of biozonation introduced by Martini for study of biostratigraphy and determination age of Qom Formation. According to distribution of the index species, created four distinct biostratigraphic marker zones in this section, described as nanno floral zones Triquetrorhabdulus carinatus zone (NN1), Discoaster druggii zone (NN2), Sphenolithus belemnos zone (NN3) and Helicosphaera ampliaperta zone (NN4). As a result of this study and based on the identified zones, the age of Qom Formation in the South East of Kashan is Late Chattian to Burdigalian/Langhian.