The three gypsum and anhydrite beds of the Blaine formation, the Medicine Lodge, Shimer, and Lovedale, respectively, which crop out at Salt Creek Canyon, Blaine County, Oklahoma, the type locality of the Blaine, were studied for the purpose of determining their origin and relationships.

Field studies were made of this area and samples were collected from each of the anhydrite and gypsum beds. Detailed megascopic, microscopic, microchemical, and petrographic examinations were made of the samples to determine their genetic relationships.

These investigations disclosed that the anhydrite, in radial form, is slowly hydrating to gypsum. No evidence of volume change during hydration was found. The conclusions reached as a result of the study are that the gypsum of the area has formed near the surface by the hydration of anhydrite; that there was no increase in volume when this hydration took place, and that the anhydrite probably was the primary precipitate in a desiccation basin, being deposited in a hot and dry climate.