The Tirgan Formation (Barremian – Aptian) is exposed in the Kopet Dagh in northeast Iran. One stratigraphic section in Zavin was measured with a thickness of 110 meters. This Formation in section consists of three parts (including lower carbonate, limy shale – marl and upper carbonate rocks). Based on the study of 94 thin sections, 10 carbonate and 2 siliciclastic lithofacies have been identified. Carbonate lithofacies were deposited in a ramp platform in fore-shoal, shoal, lagoon and tidal flat environments. Sea level changes during the early Cretaceous time led to the formation of different large scale depositional sequences Zavin (two). The present data can help in the reconstruction of the tectonic history of the area during early Cretaceous time.