ABSTRACT

All eolian origin for most of the cross-bedding seen in the blanket sandstone formations of the Colorado Plateau is generally accepted. There are, however, in the cross-bedded formations many extensive, smooth, parallel surfaces which suggest water action. These planes sharply truncate cross-bedding and obviously cannot be of depositional origin; much material has been removed in forming them. For surfaces of this type, the name multiple parallel-truncation bedding planes is proposed. Examples are seen in the Entrada, Navajo, Wingate, De Chelly, and Coconino Sandstones.

From the fact that wind has little effect upon water-saturated material it is supposed that conditions were frequently such that previously accumulated sand was removed down to the water table, thus creating the very smooth, horizontal surfaces which now separate intervals of cross-bedded sandstone. This process is to be expected in interior basins with abundant sand, strong wind action, and a water table which rises with sedimentation and occasionally reaches the surface.

Windswept, saturated surfaces such as the Great Salt Lake Desert show similar leveling effects, but here the water table is falling so a stratigraphic record is not preserved.