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
Hole in the Rock (rock formation) them along the relatively benign terrain beneath the Straight Cliffs of the Kaiparowits Plateau. However, when this led them to the 1200-foot (400 m) sandstone cliffs that surround Glen Canyon, they needed a way to cross to the eastern rim. They found (and named) Hole in the Rock, a narrow, steep, and rocky crevice and sandy slope that led down to the river. Directly across the river was Cottonwood Canyon, a tempting route up to Wilson Mesa on the other side. They worked for months to prepare the road, using blasting powder to widen the upper section and hand chisels