Bidahochi Formation

The Pliocene to Late Neogene Bidahochi Formation, lies at an elevation of about 6,300 feet (1,920 m) to 6,600 feet (2,012 m) at the southeast of the Colorado Plateau; the deposits are from Bidahochi Lake, (also called Hopi Lake), and the deposits extend southwards to the region at the north perimeter of the White Mountains of central-east Arizona. Bidahochi Lake is thought to have been a single "large lake, or several shallow, and ephemeral ones." Various fossil types are found; also bird trackways.

The Bidahochi Formation is a cliff-former unit, and exists on the Colorado Plateau as a protecting unit above the highly erodable Chinle Formation. Locally it immediately overlies other rock units. The Bidahochi Formation extends approximately 112-mi north-south, or north-northwest by south-southeast; the length is approximately equivalent to today's Great Salt Lake of Utah.

The presence of the Bidahochi Formation is a result of two factors. First it lies upon the major water divide of the (south perimeters) Chinle Wash (Chinle Valley) which flows north into the Colorado River watershed; it contrasts with the watershed to the west and south, the Little Colorado River, and the Puerco River tributary from New Mexico; the Defiance Plateau bordering the east of the Bidahochi, sheds water north, west, and south. The second is the timeframe of the Colorado River drainage through Grand Canyon, known to be about 5.5 Ma, where 5.5 Ma marks the beginning of the last deposits in the Bidahochi. The Bidahochi contains, Lower, Middle, and Upper sections, thus the drainages at the beginning of the Colorado River through Grand Canyon is coeval with the end of Bidahochi Lake deposition.