Depositional-diagenetic history of the Paleocene-Miocene successions (Jahrom and Asmari Formations) in the southern part of Dezful Embayment

Jahrom and Asmari Formations in two wells from Nargesi field in the southern part of Dezful Embayment were studied to interpret the sedimentation and diagenesis history of Paleocene-Miocene successions. A total of 14 different microfacies were identified based on the study of 270 m drilling core and 495 microscopic thin sections,which are located in four sets of open marine, shoal, lagoons and tidal flats. The microfacies of the Asmari Formation are include tidal and lagoon sets. The microfacies of the Jahrom Formation are include middle ramp and the open marine, and energetic facies of the shoal sets have been observed in abundance in this formation, and to a lesser extent has lagoon facies. According to the characteristics of the above microsfacies, it is suggested that a shallow carbonate ramp with a gentle slope be used as a sedimentation environment for these Formations in Nargesi field. Asmari Formation is deposited in the shallower parts of this ramp. The paragenetic succession of Jahrom and Asmari Formations has been interpreted based on petrographic evidence in four marine, meteoric, burial and uplifting environments, and have affected sediments, during the three stages of eogenesis, mesogenesis and telogenesis. Dolomitization, cementation, anhydritization, micriticization, neomorphism, compaction, dissolution and fracture are the predominant diagenetic processes in these Formations. Dolomitization and anhydritization processes have been observed throughout the Asmari Formation, but are less intense in the Jahrom Formation. Asmari Formation cements are mostly dolomitic and anhydrite, but Jahrom Formation cements are mostly calcite.