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Jurassic Navajo sandstone of Coyote Buttes, Utah/Arizona: coloration and diagenetic history, preservation of a dinosaur trample surface, and terrestrial analogs to Mars
The Coyote Buttes, in Jurassic Navajo Sandstone, straddles the Utah-Arizona border at the northwest margin of Vermilion Cliffs National Monument. Its spectacular geologyâ€”cyclic eolian cross strata, striking coloration, and sculpted geomorphologyâ€” makes the area one of the most popular on the Colorado Plateau. Field and laboratory techniques document three geologic features of the Coyote Buttes: sandstone diagenesis, a dinosaur trample surface, and modern iron oxide micro-concretion eolian ripples analogous to Mars. The range of red, orange, pink, and purple sandstone hues is largely due to iron oxideâ€”hematite and lesser goethite grain-coatings and cement. Six diagenetic color facies (10's m thick) document paleofluid interactions and both advective fluid flow and diffusive iron mobilization in the host rock. Bleaching patterns (cm-10's m scale) indicate advective, upward migration and accumulation of a buoyant, chemically reducing fluid (likely hydrocarbons). Liesegang bands record diffusive mass transfer across redox boundaries between a fluid enriched in mobile, ferrous iron and oxygen-rich groundwater. Coloration developed during a narrow timeframe concurrent with Laramide-aged faulting; paleofluid flow is eastward. A well-preserved dinosaur trample surface in a wet interdune interval exhibits multiple overlapping track types and sizes, high track density, footprint features, and rare tail drag marks. At least three distinct ichnogenera are present - Eubrontes, Anchisauripus, and Grallator, along with tracks of an unidentified Sauropodomorph. The trample surface refines ecologic and climatic conditions recorded in Early Jurassic eolian deposits. Complex, coarse-grained ripples of iron oxide micro-concretions derived from redox fronts are terrestrial analogs to Martian features. The ripples illuminate the history of host rock diagenesis (similar to Liesegang banding), weathering stages, and modern wind processes. These events may be scaled to Martian conditions where similar ripples are widespread and formed in a lower-density atmosphere under higher winds. The Coyote Buttes annually draw thousands of wilderness enthusiasts and photographers. This study contributes a better understanding of the area's intense diagenetic coloration and fluid history, the paleoecology of the Navajo erg, and wind dominated Martian processes. The Coyote Buttes is a valuable geologic feature for the scientific community, and an exceptional aesthetic landscape for resource management in the Vermilion Cliffs National Monument.
University of Utah;
Sandstone--Utah; Dinosaur tracks; Mars
University of Utah;
Relation-Is Version Of
Digital reproduction of “Jurassic Navajo sandstone of Coyote Buttes, Utah/Arizona: coloration and diagenetic history, preservation of a dinosaur trample surface, and terrestrial analogs to Mars” Accompanying materials available, J. Willard Marriott Library Special Collections, QE3.5 2008 .S44