The Fahliyan Formation of the Khami Group is the most important oil and gas reservoir in southwestern Iran. The formation attains a thickness of 435.5 m in the oil well X2 in Dorood oil field, Persian Gulf. It is represented mainly by thin-bedded limestones. This formation unconformably overlies the evaporate late Jurassic Hith Formation and conformably underlies the Gadvan Formation. Integrated palaeontological and sedimentological studies supported by an analysis of 150 thin-sections led to the identification of 21 benthic foraminiferal genera dominated by agglutinated forms with an additional 8 algal genera. Two foraminiferal biozones of Berriasian through Hauterivian age include the Pseudochrysalidina (Dokhania) arabica acme zone and Pseudocyclammina lituus- Coscinoconus assemblage zone, and an algal zone includes the Salpingoporella annulata range zone have been recognized. The correlation of the lower Cretaceous petroleum source rock in the Persian Gulf with regions from Tethyan Realm is limited by the lack of the analog formation that can be used for comparison. In this way, the foraminiferal zones are correlated with coeval zones in south and southwest of Iran.