Facies analysis, palaeodepositional environment and sequence stratigraphic framework of the Jahrum and Asmari formations, Fars Province, Zagros Basin, SW Iran

The Middle to Late Paleogene Zagros sedimentary basin witnessed the development of carbonate platforms teeming with large benthic foraminifera (LBF), exemplified by the Jahrum and Asmari formations in Fars Province, SW Iran. The LBF assemblage is dominated by Nummulites and Orbitolites, accompanied by smaller benthic foraminifera. In the present study, microfacies analysis, palaeoenvironmental reconstruction, and interpretation of depositional sequences/cycles in the late Eocene Jahrum and lower Miocene Asmari carbonates were conducted on the subsurface section of the Kuh-e-Mond Oil Field, located in Coastal Fars Province, within the Zagros Foreland Basin. The studied wells, designated as MD-۰۷, MD-۰۶, and MD-۰۲, exhibit respective thicknesses of ۳۳ to ۱۳۰ m for the Asmari Formation and ۳۸۲ to ۵۱۷ m for the Jahrum Formation. The interpretation of facies suggests that these intervals precipitated along a low-angle ramp-type platform in a shallow-water setting. Nine distinct microfacies have been identified, representing tidal flats, lagoons, platform margins, and shallow open marine sub-environments. Based on the integration of petrographic studies and petrophysical logs (Gamma-ray log), three depositional sequences or cycles within the Jahrum Formation (SQ A, SQ B, SQ C) in the MD-۰۷ well, and one depositional sequence or cycle within the Asmari Formation (SQ D) have been identified in the MD-۰۷, MD-۰۶, and MD-۰۲ wells. These determined depositional sequences/cycles are not only influenced by global sea level fluctuations but also impacted by the regional tectonic history, including uplift and subsidence rates.

Keywords:

Eocene , Miocene , Depositional cycle , Kuh-e-Mond anticline , coastal Fars