Carbonate platform evolution of the Asmari Formation in the east of Dezful Embayment, Zagros Basin, SW Iran

摘要

In this study, based on a multidisciplinary approach (biostratigraphy, cyclostratigraphy, and facies analysis), the Asmari carbonate successions were evaluated across two platform-to-basins transects including Parsi (Pr), Karanj (Kr), and Paranj (Prj) oil fields. In the biostratigraphy part, key large benthic foraminifera was used; which determined the Asmari carbonate Formation to the Chattian-Burdigalian in age. Facies analysis led to identifying eight microfacies (MF.1-8) arranged from basinal deep-water setting (MF.1) to lagoonal shallow-water to tidal zone (MF.8). In cyclostratigraphy, a total of seven positive breaks and five negative breaks related to 12 wells were recognized by cyclolog software, to identify and correlate coeval depositional packages across oil fields. These key breaks were calibrated with biostratigraphy dating and traced across studied oil fields. Finally, based on the combination of all extracted data, three carbonate platforms were distinguished evolved through the Chattian- Burdigalian. Chattian carbonate platform is composed of a high variety of carbonate producing (Stages I, II, and III), representing a fore-Stepping stacking pattern. Aquitanian Carbonate Platform is a soft-grained carbonate ramp with a low-angle gradient comprising two different Stages: IV and V. The Burdigalian platform (Stage VI) is composed of meters to decimetre-scale limestone (MF.6) rich in Borelis melo, discorbis, and small rotalids highlighting a shallow-water lagoon and has a uniform set throughout the study area.