ABSTRACT: The evolution of the Late Triassic Nayband Basin in central Iran was influenced by climatic changes and tectonic events. An increase in siliciclastic input and a corresponding carbonate productivity crisis in the Qhrogchi area in central Iran were initiated by the onset of a relatively humid episode in the Carnian, followed by arid to semi-arid conditions in the Norian and Rhaetian. Carbonate sediments of the Nayband Formation were deposited in a range of environments, from outer ramp to marginal marine environments. The rich benthic fauna is predominantly restricted to the limestone beds within the upper part of succession. Bivalves, hydrozoans (Heterastridium), calcareous algae, corals and sclerosponges are recorded. The latter two groups form patch reefs on the middle ramp. Benthic foraminifera show strong affinities with assemblages reported from the central Tethys, whereas others are also well-known from the Alpine region and from the eastern Tethys.