The physiographic requirements of brine production are commonly in the form of lagoons, pans, and exposed supratidal surfaces. The most common environment is the exposed salt flat or sabkha, a fairly level, salt-encrusted surface that only occasionally is inundated. Sabkhas are equilibrium geomorphic surfaces, their levels being dictated by the local level of the ground water, which rarely exceeds a depth of 1-2 m. Sabkhas are formed where eolian sand supply is limited and where hard rock lies below the level of the water-table. Particularly significant are the high rates of shoreline regression in sabkha environments. Sabkha diagenesis involves interstitial emplacement of evaporite minerals within host sediments and changes in host sediments themselves. Coastal sabkhas show diachronism of diagenesis, the evaporite-mineral belts moving progressively seaward as depositional offlap proceeds.