Nannostratigraphy of Gurpi Formation in Dare- Shahr Section (SE Ilam)

Document Type : Original Research


1 گروه زمین شناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران

2 Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran


Nannofossils are good for biostratigraphy, since they are abundant, planktonic, rapidly evolving and largely cosmopolitan, especially in the Late Cretaceous. For these reasons and due to the lack of any precise paleontological study, the nannofossils of the Gurpi Formation were investigated in Dare-Shahr. This formation consists of marl and shale and two members (Lopha and Emam Hassan limestones). In this study, for the first time, 24 genera and 48 species of nannofossils were identified. According to the stratigraphic distribution of calcareous nannoplanktons, the study section is of Late Santonian to Early Danian age, corresponding to CC16-CC26 (Sissingh 1977) and NP1-NP2 (Martini 1971). The presence of Biantolithus sparsus, Cruciplacolithus primus, Micula prinsii, indicates that the K/T boundary continues and within the Gurpi Formation in the Dare-Shahr section.