ABSTRACT: The Neyriz, Surmeh and Hith Formations outcrop in the Persian Gulf area. Assemblages of benthic foraminifera and green algae were studied in 789 meters from these formations in the onshore middle part of the Persian Gulf, South of Iran. These formations consist of grey shales, dolomite, limestone and anhydrite. The Neyriz andHith formations are barren of fossils and the age of Neyriz Formation is Early Jurassic and the age of Hith Formation is Late Jurassic (Tithonian) based on stratigraphy. In the Surmeh Formation 18 genera and 17 species of benthic foraminifera, 5 genera and 3 species of algae, one genus of bivalve and one genus of crinoid have been determined. Five biozones are defined based on the microfossil distribution, and consist of the Lithiotis Range zone, Pfenderina Range zone, Trocholina palastinensis-Trocholina Assemblage zone, Kurnubia jurassica Interval zone and the Clypeina jurassica zone. Diagnostic larger benthic foraminifera indicate a Toarcian to Tithonian age for the Surmeh Formation in this part of the Persian Gulf Basin.