OCHOAN STAGE

post-Guadalupian time of deposition of the Upper Permian Series of rock strata in the United States, characterized by the development of extensive evaporite deposits (the Permian Period lasted from about 286 to 245 million years ago). During Ochoan time, tectonism (deformation of the Earth's crust) in Mexico closed off the Midland, Marfa, and Delaware basins in the southwest from access to the Permian sea. High evaporation rates in the area resulted in a drop of the water levels in the basins, and Capitan Reef and platform areas emerged. Continued aridity caused the precipitation of anhydrite and salt in great quantities. In the Delaware Basin of southwestern Texas, the Castile Formation, consisting of laminated anhydrite, reaches a thickness of as much as 600 m (2,000 feet), whereas in the eastern portions of the basin, the Salado Formation consists of approximately 720 m (2,400 feet) of salt and interbedded anhydrite.