Document Type : Original Research Paper
Authors
1 M. Sc., Department of Geology, Ferdowsi University of Mashhad, Mashhad, Iran
2 Ph.D., Science and Research Branch, Islamic Azad University, Tehran, Iran
Abstract
Based on stratigraphic value of calcareous nannoplanktons in determing the age of sedimentary layers, they have been used for biostratigraphic studies of Surgah Formation in sadd Ilam (Ilam damp) section ,Kabir –Kuh of Ilam. This formation is composed mainly ot dark gray shales. In Type section , the thickness of the Surgah Formation is 153.7 m. 109 samples were taken from shaly layers and for the first time their calcareous nannofossils were studied.The result of taxonomic studies lead to identification of 16 family , 44 genera and 80 species. Based of first occurrence of the index species and the assemblages zones is nannofossil Zones CC13-CC15 or Uc 8- Uc 12 of standard pattern. Based on biozone,the Upper Cretaceous sediments in the study area are of the Turonian through Early Santonian ages.
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