Depositional character of Late Triassic fluvial and lacustrine strata of the Owl Rock Member (Chinle Formation), Petrified Forest National Park, Arizona.



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This study provides stratigraphic motifs and depositional reconstructions for the Late Triassic (Norian-Rhaetian) Owl Rock Member of the Chinle Formation located at Chinde Mesa, Petrified Forest National Park (PFNP), AZ. Findings are based on facies analysis, fluvial architectural element identification, stratigraphic section measurement and correlation of fluvial aggradational cycles, photo-panoramic correlation, and Fischer plot estimation of accommodation space variability. Interpreted results suggest that Owl Rock deposition was influenced by sedimentation sourcing from the Chinle Trunk River to the west and the Defiance Uplift to the northeast. Sediment contributions from the Chinle Trunk River are identified within a large-scale channel complex containing relatively mature quartz sandstones and high-flow regime sedimentary structures. Sediment contributions from the northeast are reflected by inferred topographic inversion of siliceous lacustrine, palustrine, and fluvial carbonates. Based on facies observations, the Owl Rock is interpreted to record paleoclimatic conditions of increasing seasonality and aridity during the Late Triassic.