Sedimentary environment, diagenesis and geochemistry of carbonate rocks of Bahram Formation (Middle-Late Devonian) in Qaleh-bala section (Ozbak-kuh, east of Iran)

In this research, a section of carbonate rocks of Bahram Formation in east of Ozbak-kuh village, located in north of Tabas city (Southern Khorasan Province), has been measured and studied. This sequence generally has been made of gray to bluish gray colored, thin to thick bedded limestones. Based on the filed and petrographic studies, totally 11 different carbonate microfacies have been identified. These microfacies have been deposited in five facies belts, including tidal flat, lagoon, tidal channel, shoal and open marine belts within a ramp-type carbonate platform. The most significant diagenetic processes which have been observed in Bahram Formation samples are micritization, compaction, neomorphism, cementation, dolomitization, dissolution and cavity fillings. Geochemical studies of elemental analysis of the samples show that the formation time condition of these deposits has been similar to the present temperate regions. Furthermore, these carbonate rocks have been situated in an open-system geochemically. In addition, petrographic evidences combined to the geochemical data revealed that the studied carbonate rocks have been influenced by marine, meteoric and burial diagenesis and also the effect of phreatic-meteoric diagenesis on these deposits has been more significant than the others.