Continual accumulation of concentrated saline water beneath the surface water in the Delaware basin raised the level of the highly concentrated water to the point where it caused two epoch-making events to occur in Upper Permian history. First, it stopped Capitan reef building and associated petroleum deposition. Second, it diminished the inflow of marine water and started deposition of evaporites in the Delaware basin. This point marks the close of Capitan time and the beginning of Castile time.

Subsurface study of the lower Castile formation discloses many hundred feet of depositional relief on the basin floor. This condition is responsible for unsuccessful attempts to run a structural correlation across the Delaware Basin on the base of the upper Castile (Main Salt).

At present, potash is the mineral with greatest economic importance in the Castile formation. Two mines are producing from one of the finest potash deposits in the world.

Two subsurface cross sections show many interesting features about the deposition and occurrence of evaporites.

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