Kaibab Limestone

The Kaibab Limestone is a resistant, cliff-forming Permian geologic formation across northern Arizona, southern Utah, east-central Nevada and southeastern California, best known for forming the rim of the Grand Canyon. It dates from the Leonardian to Roadian stages of the Early to Middle Permian, roughly 290 to 280 million years ago, and consists of a complex interbedded package of gypsum, limestone, dolomite, chert, siltstone and sandstone, reaching 300 to 500 feet thick in the Grand Canyon region, where its more resistant limestone and dolomite layers form prominent cliffs. It contains abundant fossils of Permian invertebrates and vertebrates, including brachiopods, corals, crinoids and giant nautiloids, and in California's Big Maria Mountains a heavily metamorphosed equivalent is known as Kaibab Marble.