Permian (Leonardian-Guadalupian) regressive peritidal to shallow-marine carbonate sequences in the Permian basin of west Texas and New Mexico contain thin, widespread quartzose sand bodies. Due to their lack of diagnostic sedimentary and biogenic features, these sand bodies are of enigmatic origin. Several lines of evidence (sedimentologic, petrographic, facies relations, Quaternary comparisons) argue against the deposition of such blanket sands by fluvial or neritic processes and for their eolian origin. Our studies indicate that such units are dominated by progradational eolian sheet deposits with lesser preserved occurrences of cross-bedded dune, wadi, and evaporite-pan facies. These facies were deposited on arid, wind-dominated exposed flats adjoining deep basins. The represent short-lived cycles of shelf emergence (sea level fall) and rapid rates of sand accumulation that interrupted longer periods of highstand carbonate sedimentation.

The low preservation potential and paucity of eolian stratification in these deposits are inherent in such depositional systems due to: (1) removal of dunes from the shelf section because of their migration to the shelf margin, and subsequent transport into adjacent basins, (2) textural homogenization by organisms and repeated periods of evaporite crystal growth disruption and dissolution, and (3) additional bioturbation and/or physical reworking as the sands prograded into outer-shelf lagoons and during subsequent shelf transgression. Thus, the absence of "typical" eolian stratification cannot be used to exclude an eolian origin for thin, widespread sands, particularly in mixed carbonate-siliciclastic shelf systems. Conceptually, the occurrence of massive sheet sands may be the sole emaining evidence of eolian activity in such systems. The implications of this model can be extended beyond this particular Permian occurrence to numerous other polylithic shelf sequences in the record.

End_of_Article - Last_Page 284------------