عنوان مقاله English
نویسندگان English
TBased on biostratigraphic studies, three assemblage biozones were identified: Oligocene (Rupelian) from the Pabdeh Formation, and Rupelian-Chattian and Chattian from the Asmari Formation, which confirms the continuity of fossil-sedimentary zones. Microfacies analysis led to the recognition of five microfacies from outer ramp, outer ramp-middle ramp transition, and middle ramp (distal part) environments, which further confirms facies continuity and the transitional nature between these two formations. By integrating the three lines of evidence (lithostratigraphy, biostratigraphy, and microfacies), it can be concluded that the Pabdeh-Asmari formation boundary in the Tang-e Chug section is completely gradual and continuous, lacking any sedimentary discontinuity or diastem. Contrary to purely lithological perspectives, this research demonstrates that the Pabdeh-Asmari boundary reflects gradual changes in the physicochemical parameters of the basin (depth, temperature, salinity, nutrients, and oxygen) during the Eocene-Oligocene transition. The coexistence of planktonic foraminifera and large hyaline benthic foraminifera in transitional microfacies indicates an intermittent oxygen minimum zone (OMZ) in the water column, comparable to modern oceanographic models along continental margins, and suggests a dynamic Zagros basin with high productivity that played a key role in the formation of source rocks and reservoirs. This conceptual framework opens new horizons for geochemical, isotopic, and hydrocarbon exploration studies in the Zagros region.
کلیدواژهها English
