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 Roan Cliffs The Roan Cliffs are a series of desert mountains and cliffs in eastern Utah and western Colorado, in the western United States that are distinct from (but closely associated with) the Book Cliffs. While Roan Cliffs are "remote and inaccessible", the Book Cliffs run along the edge of the Castle, Gunnison, and Grand valleys and are therefore readily visible from populated areas (i.e., Price and Green River in Utah and Grand Junction in Colorado) and well traveled transportation corridors (i.e., I‑70, US‑6, US‑50, and US‑191). As such the Book Cliffs are much better known than the Roan Cliffs.