Limestone forms the massive overhang above you and the ledge you are standing on. In between, softer layers of silty limestone have retreated, eroded away. All of the cliff dwelling rooms in Walnut Canyon — more than 300 — were built in natural alcoves like this.
If you have visited Grand Canyon, you have met these rocks before. This is the Kaibab Formation, the rim rock of both canyons. Below, as in Grand Canyon, are the Toroweap Formation and Coconino Sandstone.
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Notice the pattern of diagonal lines or cross-bedding in the sandstone visible directly across the canyon (and shown here). The preserved sand layers record changing wind direction.
Formed by deposits of calcium carbonate in a shallow sea near an ancient shoreline about 250 million years ago.
Formed in a near-shore environment of stream-deposited sediments and windblown sand dunes, about 265 million years ago. Windblown layers of sand were deposited on the downwind slope, at an angle.
Paleogeographic map of North America with detail of Arizona. Northern Arizona had beach front property during the Permian age, roughly 286 to 248 million years ago.