Biostratigraphy and microfacies analysis of Gadvan Formation (late Barremian-early Aptian) in Coastal Fars zone, (Zagros, SW Iran)

The investigation of lithostratigraphy, biostratigraphy and the microfacies analysis of the Gadvan Formation as an oil reservoir of Lower Cretaceous in the Zagros Basin is crucial. In this study Naser Abad section (Coastal Fars region, SW of Iran), consists of 170 meters thin to medium-bedded limestone with interbeds shale and marly limestone. According to stratigraphic distribution of identified foraminifers, two biozones are established which are: Paleorbitolina lenticularis zone and Hedbergella infracretacea Zone. Based on the investigated faunal assemblage, the age of Gadvan Formation is assigned to late Barremian-early Aptian. Microfacies studies led to the identification of five microfacies types which include: Algal-intraclast- bioclast wackestone, Intraclast- bioclast wackestone, Planktonic- bioclast wackestone, Radiolarian packstone and Orbitolina- bioclast wackestone. These microfacies show that the Gadvan Formation was deposited in both shallow water ramp and hemipelagic paleoenvironments. According to microfacies, carbonate platform of Gadvan Formation in the studied area corresponds to a moclinal platform which was affected by basement of Kazerun Fault zone.