The basis for considering the Coconino Sandstone to be of eolian origin involves numerous criteria, some of which are distinctive of an eolian environment and others merely compatible with but not diagnostic of it. No single type of evidence seems entirely conclusive, but, together, the various features present very strong evidence. The principal criteria of dune deposition are as follows:Since McKee published, additional types of terrestrial trace fossils, paleosols, and other distinctive eolian sedimentary structures have been recognized in Coconino and related eolian strata.
- The extent and homogeneity of the sand body.
- The tabular-planar and wedge-planar type and large scale of cross-stratification. The common high-angle deposits are interpreted as slipfaces on the lee sides of dunes, and the relatively rare low-angle cross-strata that dip toward the opposite quadrant apparently represent deposits of windward slopes.
- Slump marks of several varieties preserved on the steeply dipping surfaces of lee-side deposits. These are distinctive of dry sand avalanching.
- Ripple marks which are common on surfaces of high-angle crossbedding suggest eolian deposition both by their high indexes (above 15) and by their orientation with axes parallel to dip slope.
- The local preservation of a distinctive type of rain pit. Such pits illustrate the cohesion of sand grains with added moisture and a reorientation of the crater axes with respect to bedding slopes.
- Successions of miniature rises or steps ascending dip slopes of crossbeds.
- The preservation in fine sand of reptile footprints and probable millipede trails with sharp definition and clear impression.
- The consistent orientation of reptilian tracks up (not down) the steep foreset slopes.