The Dashtak and Khaneh-Kat formations in the Zagros Basin were deposited during the Triassic Period and are mainly composed of carbonate-evaporate rocks. The depositional environment of these formations ranged from supratidal and tidal flat to lagoonal and shoal ramp. However, the lack of evaporite sediments indicates that the Khaneh-Kat formation was deposited in a relatively deeper setting in which no more evaporites were present. In the study area, the Dashtak formation has acted as an effective seal for giant gas reservoirs entrapped within the Dehram Group, whereas the Khaneh-Kat formation appears to have neither of the characteristics of a cap rock. This study revealed that the Dashtak formation is divided into four sequences (middle to late Triassic) and the Khaneh-Kat formation consists of five sequences (middle to late Triassic). The uppermost sequence of the Dashtak formation was removed by post-depositional erosion in the SE despite its complete preservation in the NW. The lower part of the Khaneh-Kat formation extends throughout the basin with its carbonate facies and is equivalent to the Kangan formation. Sequences two to five of the Khaneh-Kat formation are equivalents of the Dashtak formation that were deposited in Kuh-e-Manghasht and Kuh-e-Dalani (Oshtran Kuh). These sequences showed a distinct lateral facies change from evaporite dominated facies to carbonate facies.
