Microfacies and Depositional Architecture of Lower Cretaceous (Berriasian-Hauterivian) Strata (Fahliyan Formation) in the South Zagros Basin (SW of Iran).

The Fahliyan Formation (Lower Cretaceous, Berriasian–Hauterivian) in the Zagros Basin of southwest Iran represents one of the most significant shallow-marine carbonate successions along the northeastern margin of the Arabian Plate. Detailed microfacies analysis of two subsurface stratigraphic wells (Aghar-19 and Dey-2) reveals a spectrum of 12 microfacies ranging from tidal-flat to open-marine settings. These microfacies include dolo-wackestone, stromatolite boundstone, algal intraclast wackestone foraminifer bioclast wackestone, Trocholina bioclast wackestone, Fine ooidal peloidal grainstone, coarse ooidal peloidal grainstone, intraclast ooidal grainstone, coral boundstone, bioclast packstone, bioclast wackestone, and sponge spicule bioclast wackestone, reflecting deposition across supratidal, tidal flat, lagoon, reef, fore-shoal, and slope environments. Vertical distribution of the facies demonstrates variations in paleobathymetry between the studied sections, with higher proportions of skeletal grains in the upper Aghar-19 well (~47%) and mid Dey-2 well (~50%). The abundance of skeletal components, particularly corals, benthic foraminifera, and calcareous algae, indicates favorable paleoecological conditions with sufficient light, nutrients, and normal salinity during the Early Cretaceous. These findings highlight the influence of the Late Cimmerian tectonic movements and basement faults on carbonate platform development and depositional architecture. Overall, the integrated microfacies and stratigraphic data provide new insights into the paleogeography and paleobathymetry of the Early Cretaceous Zagros Basin and underscore the significance of the Fahliyan Formation as a potential hydrocarbon reservoir. [ABSTRACT FROM AUTHOR]