Karst development and hydrogeology of Konarsiah salt diapir, south of Iran

Abstract

The Konarsiah salt diapir is located in the Simply Folded Zone of the Zagros Mountain in the south of Iran. The salt rocks in Konarsiah diapir belong to the Hormuz Formation (Upper Precambrian–Middle Cambrian). Salt extruding from two nearby vents along the same fault have merged into a single body. The grey salt is covered by brown residual cap soils (4–32 m) and blocks (up to tens of meters) of the low-solubility components of the Hormuz Formation. The visible karst features are extensive sinkholes, a few shafts, and inlet caves. Sinkholes are mainly due to soil-cover and caprock collapse and do not show any preferential spatial pattern. Several maps, including salt outcrops, thickness of the mantling soils, salt table (the contact elevation between salt layer and cap soil), and sinkhole distribution are presented. The diapir has been divided into four zones based on the surface slope, cap soil thickness, sinkhole area ratio, and the size and density of sinkholes. Surface slope and cap soil thickness are the main parameters that differentiate the sinkholes. The general direction of groundwater flow is downslope towards the adjacent Konarsiah Plain in the south with diversions towards brine springs, and adjacent alluvium and karst aquifers. The type of groundwater flow is dominantly diffuse. Cave and conduit development is inhibited due to rapid saturation of recharge water with respect to halite. The numerous discharging zones and the constant flow rate of brine springs confirm a diffuse flow model proposed for the hydrology of the Konarsiah salt diapir.