Yellow Rock, Cottonwood Canyon Road, Utah

October 06, 2011


Photographer: Thomas McGuire; Thomas McGuire's Web Site
Summary Author: Thomas McGuire

The Navajo Sandstone is a prominent rock formation of the Colorado Plateau of the western U.S. Such features as crossbedding rock arches and natural bridges, slot canyons, polygonal jointing in sandstone "slickrock" surfaces and concretions (Moqui Marbles) are common in Navajo Sandstone formations. In fact, the Navajo Sandstone has been featured in more than a dozen Earth Science Picture of the Day images over the past decade. It's especially well exposed throughout southern Utah and particularly in the Escalante-Grand Staircase National Monument. Relatively pure quartz sandstone it is often white to light tan, but the "Navajo" is typically colored pink or red by as little as 0.5% iron oxide filling the pore space.  In some locations, such as the remote exposure above known as Yellow Rock, limonite, a mix of hydrated iron oxides, gives the sandstone an over-all yellow color. This location also shows bands of red and white that don't follow depositional layers but rather shows past groundwater circulation.

The photo above shows the author sitting near the summit of Yellow Rock in the Cockscomb Monocline. Orange and yellow are evident here in the Navajo Sandstone. Beyond are while layers of the same formation and the rusty red Kayenta Formation. The cliff on the right descends into Hackberry Slot Canyon.

Photo details: Fujifilm; FinePix S9000 camera; tripod and 10s delay; f 6.4; 1/400 second exposure.