Slabs of rippled Moenkopi rock lie beside a paved pullout near Slickrock Divide. They preserve the surface of ancient river bottoms and tidal mudflats, and some carry mud cracks and swim marks left by reptiles crossing shallow water. Collecting any rock here is illegal.
Take your phone and walk to the nearest slab. If I cut out when the car goes off, tap play. Lay your hand flat on it. Those ridges are a river bottom or a tidal mudflat of the Moenkopi, preserved in stone. Many of these slabs carry mud cracks too, from pools drying under a hot sun, and some carry swim smears, the marks of extinct reptiles crossing shallow water. Find one with clean ripples and follow a single crest with your finger until it runs out. About two hundred fifty million years ago, that was a wet afternoon. In places this formation runs more than nine hundred fifty feet thick, silt and clay settled out in lagoons and mud flats. Here's why that matters on a road about the Fold. This is the same rock as the Fluted Wall on Highway twenty-four, laid down as a flat tidal shore. The same push that raised the west side of the Fold took this mud, and all the rock stacked on top of it, and tipped the whole pile. Look all you like. Collecting is illegal, and that goes for every chip. You're standing on the evidence.
Photo: NPS / E. Van Ness · Public domain (U.S. Government work)