ORIGINAL ARTICLE Karst hydrogeology of Karmustadj salt diapir, southern Iran Esmaeil Nekouei 1 • Mehdi Zarei 1 Accepted: 16 March 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract Karmustadj salt diapir (KSD) is located in the arid region of southern Iran. The karstic features of the KSD including vertical shafts, sinkholes, caves and brine springs, were investigated in order to characterize groundwater flow system in the diapir. KSD drains by three perennial and several temporary brine springs saturated with respect to halite. Electrical conductivity and chemical composition of three perennial brine springs were mea- sured in wet and dry hydrological seasons. KSD consists of two hydrogeological units of Plug and Glacier districts. A conduit karst flow system is characterized for the Plug district including point recharge through sinkholes and discharge as several temporary brine springs. For the Glacier district, a diffuse flow system is proposed. Rainfall recharged to Glacier district discharges mainly via three brine springs throughout the year. The higher elevation of the springs of the diapir indicates that the elevation of base level of karstification is higher than the surrounding area, i.e. subsurface discharge of brine to the adjacent aquifers is unlikely. In this condition, construction of evaporite basins is proposed to prohibit re-infiltration of the emerged brine of the diapir into the surrounding aquifers which would increase water quality of the aquifers. Keywords Karmustadj salt diapir Á Brine springs Á Karstic features Á Karst flow system Introduction Salt diapirs are mostly reported in the United States (the Gulf Coast region and southeast Utah), Iran, the Dead Sea coasts, the north German Plain, northeast Spain, Albania, southwest of the former Soviet Union, west central Africa, and Tunisia (Frumkin 1994; Bosa ´k 1998; Johnson 1997; Talbot 1998; Hamlin 2006; Lucha et al. 2008). The emergence of more than 122 salt diapirs in southern Iran makes the region a distinguished territory of exposed salt diapirs in the world (Zarei 2015). Formation of salt diapirs is the result of vertically upward intrusion of more mobile and ductile salt layer through brittle overlying strata. Salt rock has lower density in comparison with the typical geological formations. This density difference reveals as a force of buoyancy which results to pierce of underlying salt strata to the surface. Salt rock is significantly soluble (360 g/L), but imper- meable such that no groundwater flow occurs within salt itself (Anderson and Browns 1992; Ford and Williams 2007). Water infiltrates over or through salt and dissolves the extremely soluble rock which causes formation of a solutional pathways to flow infiltrated water through the salt diapirs (Frumkin 1998, 2000). Bosa ´k et al. (1999) studied about 60 salt diapirs of Hormuzgan Province, southern Iran. They generally eval- uated the karstic features of the studied salt diapirs and they introduced karrens, dolines, uvalas, dry valleyes and brine springs as the most significant karst features of the Iranian salt diapirs. Mehdizadeh et al. (2015) studied 62 salt diapirs of Fars Province (southern Iran). They investigated how diapir-derived brine influences the water quality of the adjacent aquifers. In addition, Zarei (2015) characterized the factors controlling impacts of salt diapirs on water quality of the surrounding aquifers include salt diapir & Mehdi Zarei zareim@shirazu.ac.ir 1 Department of Earth Sciences, Shiraz University, Shiraz, Iran 123 Carbonates Evaporites DOI 10.1007/s13146-016-0298-1