Permian DeChelly Sandstone forms the steep cliffs of the buttes in Monument Valley, Navajo Nation, Colorado Plateau. Only a short distance to the north, near Mexican Hat, the DeChelly (pronounced de shay) Sandstone becomes much thinner and less resistant as you approach the late Paleozoic Paradox Basin. The underlying Organ Rock Shale holds upt the slopes at the base of one of the Mitten Buttes in the distance.