Photographs

FIG. 24.  Scalloped cross-bedding inferred to have been produced by a dune undergoing cyclic fluctuations in height or asymmetry and migration speed; eolian deposits in the Navajo Sandstone (Upper Triassic? and Jurassic) in Water Holes Canyon, Arizona.

RECOGNITION: Measurements in the field show that the cross-beds and bounding surfaces in this cross-stratified bed have the same strike, thereby demonstrating that the cyclicity of the bedding was produced by cyclic flows rather than superimposed bedforms.  The cyclic flows are inferred to have caused the dunes to vary in height, as illustrated in Figure 16, or to vary in asymmetry and migration speed as is illustrated in Figure 22B.