The Cretaceous Ocozocuautla Formation of central Chiapas, Mexico, exhibits a cyclic arrangement of sediments in a 100-m. interval near the top of the formation. Each cycle is divided into a basal redbed unit, middle gray shale, and upper limestone or calcareous siltstone. These cycles are thought to be caused by minor lateral migration of the strand in response to variation in supply of sediment accompanied by uniform subsidence of the area. The cycles are superimposed on a major transgression and are compared with similar rhythmically deposited sediments of the Jurassic Carmel Formation in Utah. It is concluded that the Ocozocuautla and Carmel cycles are very similar but that because the former represents a transgressive phase and the latter a regressive phase, the actual arrangement of individual members within each cycle is reversed.

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