Coconino Sandstone

The Coconino Sandstone is a Permian geologic formation of light-colored, wind-deposited quartz arenite found in northern Arizona and southern Utah, across the Colorado and Coconino plateaus, prominent in the upper walls of the Grand Canyon, where it forms sheer cliffs. Dating to the Kungurian stage, roughly 275 million years ago, it is composed of well-sorted, uniformly fine-grained quartz sand cemented by silica, pale white to buff in color though sometimes brownish or red where iron-stained, and reaches 65 to 300 feet thick in the Grand Canyon region; it was named by Darton in 1910 for the Coconino Plateau. The formation preserves large-scale cross-bedding along with ripple marks, raindrop impressions and slump marks, and is noted for abundant fossil trackways of terrestrial invertebrates and vertebrates that record its origin as a desert sand dune field.