Tapeats Sandstone

The Tapeats Sandstone is a Cambrian geologic formation of the southwestern United States, exposed in the Grand Canyon of northern Arizona as well as central Arizona, southeast California, southern Nevada and southeast Utah, dating to about 508 to 507 million years ago, with some researchers placing its maximum depositional age closer to 505 to 501 million years. It consists of medium- to coarse-grained, thin-bedded, cliff-forming sandstone that is locally conglomeratic, reaching about 70 meters at its thickest, and forms the basal unit of the Tonto Group, typically marking the lowest Phanerozoic strata above the Great Unconformity in the Grand Canyon. Its lower and middle beds form resistant cliffs above the underlying Precambrian rock, while its upper beds form the surface of the Tonto Platform, across which the Tonto Trail runs.