Sedimentary strata of Middle Permian age (Guadalupian--uppermost Leonardian?) in the central western United States (Montana-North Dakota to Arizona-West Texas) contain a variety of rock types, including carbonates, evaporites, and terrigenous clastics. These strata include such group or formational units as Phosphoria, Park City, Goose Egg (Wyoming); Taloga, Whitehorse, Blaine (Kansas, Oklahoma); Artesia, San Andres (West Texas, New Mexico); and Kaibab (Arizona). These sediments were deposited on a broad cratonic shelf which underwent differential subsidence and which was bounded by a continental upland on the east and by deep-water seas on the west and south. Lithologic patterns within the strata are characterized by profound lateral facies changes and cyclical repetitio s in vertical sequence. Lateral lithofacies changes are related to a broad range of depositional environments and processes, many of which may be identified. These lithofacies changes control the accumulation of major quantities of oil and gas. Cyclic repetitions of lithology in vertical sequences of the strata are related to periods of transgression and regression produced by changes in sediment productivity and sea level. These changes may have been controlled by both global tectonic instability and polar glaciation. Regional correlations based on the cyclicity of the strata seem reasonable and suggest that several of the major depositional cycles identified in widely scattered parts of the central western United States may be synchronous.

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