Diagenetic aspects of the Lower Paleocene Sachun Formation carbonates, Zagros Basin, southwestern Iran

The Sachun Formation in the Zagros Mountains Ranges was sampled on the basis of changes in lithology and 150 vertically oriented thin-sections were prepared and subjected to detailed petrographic study. Evaporite, carbonate and shale/marl facies are identified here. These facies which have been laid in 4 facies belts of supratidal, intertidal, lagoon and barrier, deposited on a ramp platform. Petrographic studies showed that the Sachun Formation has had a complex diagenetic history. The following diagenetic events occurred in the carbonate microfacies: micritization, dissolution, silicification, dolomitization, hematitization, compaction, fracturing and stylolitization. The diagenetic features observed petrographically in the carbonate microfacies represent changes which took place under three diagenetic environments (eogenic, mesogenic, and telogenic) with three different marine, burial, and meteoric diagenetic conditions. The diagenetic sequence of events that affected the Sachun Formation includes micritization and micrite envelope features which have been reported from an eogenic/marine environment.