The Navajo sandstone has not been securely dated. It is either from the end of the Triassic Period or the beginning of the Jurassic. It is usually treated as part of the Triassic because the Navajo shows erosion on the top layer before the next, the Carmel Formation was deposited. This sharp break in the bedding at the erosional surface is called a disconformity.
The Navajo sandstone is formed from huge dune beds, beds of windblown sand, the great Navajo desert, as large as today's Sahara. The dunes were interupted only occasionally by shallow interdunal lakes, the evidence of which is seen in thin limestone and siltstone layers seen in small areas within the dune field. This sandstone is characterized by large scale, high angle cross-stratification of the rock in very conspicuous wedge shapes. The sandstone is usually white with very fine uniform grains of almost pure quartz sand.
This sandstone is relatively easily eroded, but can make high cliffs in the right circumstances, as in Zion National Park and along the Escalante River. It is usually seen in rounded domes, as at Capital Reef, along the Burr Trail and the drive from Boulder, UT to Escalante. The formation pinches out to the east before the San Juan Mountains are reached.
