干旱区生态环境知识资源中心

This study focuses on the karstic groundwater of two main zones of Iran: Keyno anticline (Zagros Range) and Shotori Mountains (Central Iran). Mean annual precipitation of these areas is 1100 and 150 mm, respectively. The major carbonate rocks of Shotori Mountains consist of the Permian Jamal formation limestones, the middle Triassic Shotori formation dolomites, and middle to upper Jurassic Esfandiar formation grey limestones. Results of isotope analysis demonstrated that samples do not show serious evaporation effect and rain directly infiltrates into aquifers. By analyzing the hydrographs of karst springs, it is revealed that the contribution of quick flow is less than 33 % in all of them. Relatively stable discharge and electrical conductivity, low recession coefficients, and high base flow component imply a diffuse system in related aquifers. According to these studies, it seems that there is no developed karst system in Shotori Mountains, and some large voids observed in well logs can be attributed to the paleoclimate. Because of the complexity in structure and very low precipitation, the Shotori Mountains have many differences compared to other karstic area of Iran, such as the Zagros belt. Geomorphology studies show obvious differences between karstic features in this area and typical karstic area. There are not any advanced morphological karst features such as poljes and sinkholes and other typical features (rill karren, runnel karren, etc.) replace with vespiary features, microspitz karren, and similar features. Purity of limestone in Shotori Mountains is the same as Zagros, and then the main reason for morphological differences can be attributed to the lower precipitation in Shotori area. On the other hand, the main controlling factor in valley generation in this area is tectonic (faults and rejuvenation); therefore, there are no real karstic valleys.