Abstract:

Karstified carbonate formations are among the most important water resources in the south-central regions of Iran. If the karst water is not contaminated by salt domes, the electrical conductivity of water in the karst aquifer is less than 500 µS cm-1 in the south-center of Iran. The study area is located in the southern flank of Shahneshin-Milk anticline, 200 km east of Shiraz. This region is situated in the Zagros Thrust Zone. The Tarbur karstic formation (Late Campanian-Maastrichtian) is outcropped on the southern flank of the Shahneshin-Milk anticline which is underlain by the impermeable Radiolarite formation. The Darab salt dome outcrops inside the karstified Tarbur Formation. Several springs emerge from the Tarbur Formation. The quality of all springs is in the range of unpolluted karst water except for three springs which are located near the Darab salt dome. The electrical conductivity of these springs range from 1200 to 2000 µS cm-1. Part of the alluvium near the Darab salt dome is salt-marsh which is bounded by two channels. The electrical conductivity in the salt-marsh below the water table is about 1400 µS cm-1, and it reduces to 400 µS cm-1 at the lower depths. Run-off from the Darab salt dome and seepage from the channel with low quality water are probably the main reasons of salt-marsh development. A considerable amount of polluted Tarbur karst water does not flow towards the marshland because, firstly, most of the Tarbur karst water discharges from the springs, and secondly, the alluvium aquifer is not affected by polluted water at lower depths.