Nannostratigraphy of the Dalichai Formation in the Naviya section of Kopet Dagh Mountain Range in Iran

摘要

For the first time, the calcareous nannofossils of the Dalichai Formation have been studied. The Dalichai Formation, which contains oil and gas reserves, is a well-bedded greenish-gray, tarry (bituminous), pyritic, marly shale with thin layers of limestone (Afshar-Harb, 1979). The Dalichai Formation is overlain by the Lar Formation and is underlain by the Kashaf Rud Formation. A total of 110 samples were examined, and nannofossil species were well preserved. In this study, 37 species belonging to 23 genera and 11 families were recorded. Using ammonites, previous workers assigned an Oxfordian-Kimmeridgian age to this formation. Using the first and last occurrences of calcareous nannofossils, the age of the Dalichai Formation is lower Bajocian-Tithonian/Berriasian in the Naviya section, which corresponds to Zones Nj9-Nj18/CCl of Bown(1998).