ABSTRACT

Throughout its outcrop in southeastern Utah, the Permian Cedar Mesa Sandstone contains large-scale crossbedding and is devoid of marine fossils except for sand-size skeletal fragments. Although this rock unit has been interpreted by several recent workers as shallow-marine, stratification identical to that documented in modern eolian dunes is ubiquitous in the Cedar Mesa. Thin, inversegraded laminations within crossbeds represent the unique product of climbing wind ripples. This type of stratification is the best evidence for an eolian origin of the Cedar Mesa; such an interpretation is strongly supported by other evidence. Vertebrate trackways and simple, small, cylindrical burrows constitute a distinctively nonmarine ichnofauna. Rhizoliths ("root casts") are abundant at many stratig aphic levels. In the underlying Rico and Hermosa formations, sandstones with physical and biogenic sedimentary structures identical to those in the Cedar Mesa are interbedded with crossbedded limestones with abundant megafossils and marine traces. Contacts between sandstones and limestones are sharp; gradational relationships would be expected if both sandstones and limestones accumulated subaqueously. Siliciclastic pebbles are present in some of these carbonate rocks, suggesting that the well-sorted nature of the sandstones cannot be attributed to the unavailability of coarse clasts. Palcocurrent data from the sandstones and limestones show significantly different vector means and variance. Southward pinchout of marine carbonates indicates that winds were onshore. Winnowing of silicicla tics from coarser carbonate detritus created a strong dichotomy in bulk mineralogy between marine and eolian sediments. Reinterpretation of the sandstones necessitates reappraisal of ideas concerning the mineralogical maturity of these sediments. The relative importance of eolian and shallow-marine transport processes to the destruction of labile siliciclastics is unknown.