The Asmari Formation in the Lorestan Zone of the northwestern Zagros has recorded a complex carbonate–evaporite depositional system influenced by accommodation, hydrodynamic energy, and carbonate production. Although widely interpreted as a carbonate ramp, the controls on evaporite development and its relationships with facies distribution and sequence architecture remain poorly constrained. This study investigates the depositional evolution of the Asmari Formation through integrated lithostratigraphic, microfacies, petrographic, and sequence stratigraphic analyses of 1,154 thin sections from three outcrop sections and one exploration well. Eleven microfacies representing open marine, shallow-water, lagoonal, tidal-flat, and evaporitic environments were identified and grouped into five facies associations, and three depositional sequences were recognized. Results show a laterally heterogeneous carbonate ramp, with open marine facies passing into shallow, restricted lagoonal, and peritidal environments. The Kalhur Member records the strongest restriction, with thick evaporites, hopper halite, and chevron-growth fabrics indicating a subaqueous saltern-type system under restricted marine circulation and high evaporation. Marked lateral variations in evaporite thickness, particularly the exceptional development of the Upper Kalhur Member in Well DL, indicate that spatially variable accommodation influenced sediment accumulation and preservation. Results show that the Asmari evolution reflects the interaction of relative sea-level changes, accommodation, marine restriction, and carbonate production processes through time.