The Cambrian Muav Limestone is a geologic unit within the 5-member Tonto Group. It is about 650 feet (198 m) thick at its maximum. It is a resistant cliff-forming unit. The Muav consists of dark to light-gray, brown, and orange red limestone with dolomite and calcareous mudstone. The Muav Limestone is overlain in the western Grand Canyon by the late Cambrian Frenchman Mountain Dolostone. Eastward, the Frenchman Mountain Dolostone pinches out and the Mississippian Redwall Limestone, which forms prominent vertical cliffs, directly lies upon the Muav Limestone. The Devonian Temple Butte Formation fill deep paleovalleys that have been cut through the Frenchman Mountain Dolostone and into the Muav Limestone.