The Dox Formation, the fourth from the bottom member of the Grand Canyon Supergroup, is thick and wide. The layers of deposits that make up the Dox are estimated to be about 3000 feet deep, and since most of the Dox is soft and easily eroded, the inner canyon widens out dramatically where the Colorado River flows through it. Upstream in the Marble Canyon, where the Colorado flows through the hard, resistant Muav and Redwall Limestone, steep cliffs rise up directly from the river. Downstream, where the the Colorado flows though the Vishnu Complex, the river is again confined to a narrow inner canyon dug out from the Tonto Platform. But in the southeastern portion of the canyon visible from Desert View, you can see the river winding its way though a wide valley of the Dox all the way from the rim.
The Dox Formation appears in scattered locations throughout the Grand Canyon, but, as part of the Grand Canyon Supergroup, is always deep in the canyon somewhere below the Tapeats Sandstone and the Great Unconformity. You encounter bits of it on the North Kaibab and North Bass trails and can see it in other places, but it is the dominant formation of the eastern inner Grand Canyon, and you will travel though long stretches of it on the Tanner and Beamer trails and on the Escalante Route.Here, at Comanche Point high above the river on the rim of the Palisades of the Desert, you look down on a wide, purplish valley, with the Colorado River lazily winding its way through it. The Escalante Route wanders through the expanse of the Dox for nine miles starting at Tanner Rapids, near the center of the picture. The Tanner Trail comes in from the left, its final mile and a half down to Tanner Rapids below the Tapeats Sandstone entirely in the Dox. The Beamer Trail starts at Tanner Rapids and heads off to the right, remaining in the Dox along the river for 3 miles before finally climbing up higher on its way to the Little Colorado River. Here we are on the Tanner Trail, about half way down through the descent of the Dox. We are in a portion of the Dox called the Comanche Point Member that is particularly soft. You are walking on a fine gravel that feels much like walking on a trail of decomposed granite in a neighborhood park. On the far side of Tanner Wash you can see the fine banding of grays, blacks, and purples that you see in the Dox throughout this area. Also note that you don’t see much plant life. Blackbrush and other shrubs don’t seem to like the Dox, so you just see scattered clumps of grass and small patches of cactus. This spot is on the Escalante Route, overlooking the delta of Unkar Creek just across the river. The Escalante Route at this point is tracking on top of another portion of the Dox called the Solomon Temple Member, which at its top is made up of much more resistant sandstone that forms steep slopes. Just upstream the Colorado has curved back into those slopes, creating a sheer cliff of several hundred feet, so steep that if you go there and want to safely peer over the edge, you have to lay flat on your belly and poke your head out over the abyss. Look past the cliffs beyond the river and you see the same characteristic banding of the Dox you see from the Tanner Trail. But also notice the slope of the bands. All of the Dox, and indeed all of a whole sequence of formations in the Grand Canyon Supergroup, maintain this same slope of about ten degrees for many miles downstream. Here we are a couple of miles further along the Escalante Route, though we are now much higher above the river. We are still tracking just above the steep slopes and cliffs of the Solomon Temple Member, but that 10 degree slope has pushed us up to this high point, almost all the way up to the Tapeats Sandstone. Notice that the Dox along the river in the bottom of the picture is getting much darker, and the Dox will continue to darken as we head deeper into it.
I consider this spot, with the magenta cliffs, the green or blue or brown or whatever it may be at the moment river in the foreground, and the high cliffs of the Palisades of the Desert in the distance, one of the most beautiful spots in the entire Grand Canyon.Further southwest along the Escalante Route, we are here in the lowest portion of the Dox Formation, called the Escalante Creek member. The Dox has become much darker, and the route through it steps up and down on slopes, and since there aren’t any significant cliff bands its easy enough to get through it. The yellow, dried up plants covering the slopes are brittlebush, and this area must be magnificent following a good rain in the spring, when a sea of yellow brittlebush blossoms coat the dark slopes.
To read more detailed geological information about the Dox Formation, visit the Wikipedia page for the Dox Formation.