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Coconino Sandstone is a geologic formation that spreads across the Colorado Plateau province of the United States, including northern Arizona, northwest Colorado, Nevada, and Utah.

This rock formation is particularly prominent in southeastern Utah, where it can be seen in a number of national parks and monuments, including Zion National Park, Capitol Reef National Park, the San Rafael Swell, and Canyonlands National Park. It is also present in the Grand Canyon, where it is visible as a prominent white cliff forming layer. Coconino sandstone frequently appears just below the Kaibab Limestone or the Toroweap layer. Coconino layers are typically buff to white in color, believed by many to be the remnants of eolian (wind-deposited) sand dunes deposited approximately 260 million years ago.

Others, however, suggest that fossil tracks in the Grand Canyon's Coconino Sandstone point to underwater deposition, rather than desert wind deposition of dry sand. Because many of the tracks have characteristics that are "just about impossible" to explain unless the animals were moving underwater, Dr. Leonard Brand has suggested that newt-like animals made the tracks while walking under water and being pushed by a current. To test his ideas, he and his colleague videotaped living newts walking through a laboratory tank with running water. All 238 trackways made by the newts had features similar to the fossilized trackways in the Coconino Sandstone, and their videotaped behaviour while making the trackways thus indicated how the animals that made the fossilized trackways might have been moving.

Putting together all of his observations, Dr. Brand thus came to the conclusion that the configurations and characteristics of the animals trackways made on the submerged sand surfaces most closely resembled the fossilized quadruped trackways of the Coconino Sandstone. Indeed, when the locomotion behaviour of the living amphibians is taken into account, the fossilized trackways can be interpreted as implying that the animals must have been entirely under water (not swimming at the surface) and moving upslope (against the current) in an attempt to get out of the water.

1. McKee, E. D., 1979. "A study of global sand seas: Ancient sandstones considered to be eolian." U. S. Geological Survey Professional Paper 1052, Reston, VA: USGS.
2. Geology Today, vol. 8(3), May–June 1992, pp, 78–79 (Wet tracks).
3. Monastersky, R., 1992. "Wading newts may explain enigmatic tracks." Science News, vol. 141 (1), p. 5.
4. Brand, L.R. and Tang, T., 1991. "Fossil vertebrate footprints in the Coconino Sandstone (Permian) of northern Arizona: Evidence for underwater origin." Geology, vol. 19, pp. 1201–1204.

• Sedimentary rocks
• Geologic formations
• Geology of Arizona
• Geology of Colorado
• Geology of Nevada
• Geology of Utah