The Structure of Salt Formations

Abstract

This chapter discusses the structure of salt formations. Massive salt beds are formed in layers above sedimentary rocks by the evaporation of lake waters in arid regions or in lagoons near the ocean. The salt beds may be interbedded with layers of shale, limestone, and other sedimentary rocks because of cyclic changes in the climate from humid to dry over geologic time. Salt formed in land-locked basins has a composition that reflects the chemical nature of the surrounding rocks. It may contain useful amounts of gypsum and potash that may be mined economically. On the other hand, salt formed in lagoons may have a high content of pure salt. The chapter illustrates bodies of salt formed in the shape of domes. The salt domes originate from thick beds of salt buried deep under the layers of sedimentary rocks, at depths of 10 km or more. As salt is lighter in weight than the overlying sediments, a large amount of salt shaped like a matchstick may slice its way upward through the sediments.