Lower-Middle Triassic carbonate platform sedimentary environment in the large anticline of Gadamgah in south of central Alborz

The Elika Formation forms the major part of the Triassic carbonate sediments in the Alborz basin. In this study, facies and sedimentary environments of this formation were studied in Shahmirzad section whith a thickness of 746 meters and in Zereshk-Darreh section whith a thickness of 756 meters in the southern part of central Alborz. Based on facies studies, four carbonate facies associations (tidal tlat, shoal, lagoon and open marine) have been identified, including twelve carbonate microfacies and have been deposited in a carbonate ramp. Deposition of sediments in this sequence can be divided into three stages. In the first stage, most of vermiculate limestone deposits are composed of bioturbated mudstone and clotted peloidal mudstone. The high frequency of facies such as laminated stromatolite, intraclastic packstone-grainstone and laminated mudstone are characteristic features of the second stage of sedimentation (middle dolomite) and indicate a decrease in the depth of sedimentary environment. In the third stage, the environment was suitable for the expansion of barriers and formation of packstone-grainstone facies.