The Alborz range in the north of Iran, is part of the Alps-Himalaya fold-thrust belt. A succession of Middle Jurassic to Late Cretaceous rocks is lithologically very similar to time equivalent sediments in the Kopet-Dogh fold-thrust belt and named “northern facies” by Ghasemi (1990)(Alavi 1996). This succession is on the northern slope of eastern Alborz. In the south of Kordkuy town, a part of this succession is exposed and unconformably overlies the Carboniferous carbonate sediments (Mobarak & Ghezel-Ghaleh Formations) and consists of chalky limestone and marl. The lowermost sediment is 2 km from northern ChamanSsaver and has been studied in three sections. Paleontological studies in this area are few and based on benthic foraminifera and rudists. For the first time the calcareous nannofossils in this area were studied. For this purpose we took 23 samples for examination. The nannofossils are moderately to poorly-preserved and diverse. As a result of this study, 14 genera and 26 species of nannofossils have been identified and photographed. The predominant species in all sections are Watznaueria biporta, Uniplanarius trifidus, Lucianorhabdus cayuxii and Lucianorhabdus maleformis. Based on the predominant species, Uniplanarius trifidus, in the lowermost sections the succession is thought to have been overthrusted by Carboniferous carbonate sediments after the Late Campanian.

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