The evaporitic carbonates can be subdivided into three units: a boxwork boundstone unit, a veneer boundstone unit, and an algal boundstone unit. These units contain tepees, stromatolites, and mound springs, which show a megapolygonal outcrop pattern. They formed under a hydrological regime that has changed little in 6000 years. Consequently it is possible to interpret the hydrological significance of carbonates. The salinas are filled by schizohaline surface waters whose water levels and salinities fluctuate seasonally. All of the salina carbonates for where marine-derived groundwater resurges from a surrounding dune aquifer into the margin of the salina. Tepee structures form in the veneer boundstone as a response to groundwater-induced seasonal changes in the pore pressures of the underlying boxwork sediments. The recognition of such groundwater tepees in ancient carbonate sequences could aid paleohydrological interpretation of the ancient basin.--Modified journal abstract.