Determining microfacies of phosphate bearing Pabdeh Formation in paleogene carbonate ramp of Lar anticline (Northeast of Gachsaran)

Pabdeh Formation comprised carbonate-siliciclastic succession of Zagros fold-thrust belt in south west of Iran. The studied area is located in Lar Mountains (North East of Khami anticline) which extend in a northwest-southeast direction Parallel to the Zagros sedimentary basin trend. Microfacies analysis especially in phosphate-bearing horizons and semiquantitative investigations of foraminiferal contents as an aid to determining the depositional environment of marine deposits was the aim of this study. For this purpose, 300 sample were collected from 410-m stratigraphical section in the Pabdeh Formation. From these 126 thin section were compiled based on lithology and facies alternations. Petrographical studies and microfacies analysis of Pabdeh Formation demonstrate that eight lithofacies can be recognized in this interval. Planktonic Foraminiferal mudstone and indicating the presence of turbidite microfacies suggest deposition in a ramp setting. On the other words the depositional environment of the Pabdeh Formation evolved into an outer ramp setting. Microfacies of the upper part of Pabdeh Formation reveal deposition in a shallowing-upward depositional environment. With attention to the items mentioned above the Pabdeh Formation is dominated by a pelagic microfauna that deposited in a deep ramp setting (Outer ramp) which passed into a shallower ramp parts (Middle ramp).