IntroductionThe Lut Block is alsom called the "Median Mass of East Iran". This basin is a region characterized by Jurassic-Cretaceous-Tertiary sequence (Stocklin and Nabavi, 1973). In this research, to determine the age of these sequence in the Sarayan region (Rumeshtik section), a detailed study of calcareous nannofossils under optical microscope was performed. This section, based on the structural classification of Iran, is located in…