Microfacies, depositional environments and sequence stratigraphy of the Oilgo-Miocene Asmari Formation in the Kupal Oil Field, Central Dezful Embayment

The Asmari Formation in the Kupal Oil Field is composed of fossiliferous limestone، dolomitic limestone، argillaceous limestone، sandstone and shale. It is the major reservoir rock of Iran in several oil elds of the Zagros. The age of Asmari Formation in this oil eld is Oligo-Miocene (Chattian–Burdigalian). In this research، depositional environments and sequence stratigraphy of this time interval are studied in 3 subsurface sections using cores، thin sections and cuttings. Based on this study، 9 carbonate microfacies and 2 siliciclastic lithofacies are recognized. These sediments are deposited in a homoclinal ramp including inner ramp (A1-A7)، mid ramp (A8) and outer ramp (shale and A9) sub-environments. Rapid changes of deep marine facies to lagoonal and/or tidal at/sabkha conditions، suggest a restricted sedimentary basin. Based on microfacies analysis، stacking pattern and sequence boundaries، 4 third- order depositional sequences have been recognized. The interpreted sea level curve can relatively be correlated with global sea level changes and the differences are related to local and regional structural events.