Organ Rock Formation Organ Rock Formation The Organ Rock Formation or Organ Rock Shale is a formation within the late Pennsylvanian to early Permian Cutler Group and is deposited across southeastern Utah, northwestern New Mexico, and northeastern Arizona. This formation notably outcrops around Canyonlands National Park, Natural Bridges National Monument, and Monument Valley. The age of the Organ Rock is constrained to the latter half of the Cisuralian Epoch by age dates from overlying and underlying formations. Important early terrestrial vertebrate fossils have been recovered from this formation in northern Arizona, southern Utah, and northern New Mexico. These include the iconic Permian terrestrial
Roan Cliffs In addition, the name Book Cliffs is often applied to both landforms, with Roan Cliffs being an alternate name. Moreover, because of the how far they are spread between Utah and Colorado, they are sometimes mistakenly believed to be separate landforms of the same name within each state. The Roan Cliffs are situated north of (in back of) and above, but run roughly parallel to, the Book Cliffs. Stretching nearly from west to east, the Roan Cliffs begin on southern edge of the West Tavaputs Plateau, on the eastern edge of the Willow Creek (and the US‑191 corridor), north of