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
Straight Cliffs Formation are known to contain marine invertebrate fauna because the Smoky Hollow and Drip Tank Member were deposited in terrestrial settings. The Tibbet Canyon Member was initially dated based a middle Turonian index fossil "Inoceramus howelli" which indicates the "Prionocyclus hyatti" ammonite zone. A variety of invertebrate fossils have been found in the John Henry Member including the ammonite "Baculites codyensis" and the bivalve "Endocostea baltica". Analysis of foraminifera and ostracods has helped refine depositional environment interpretations for a variety of shallow marine sub-environments such as lagoons, bays, and estuaries Vertebrate fossils have been found throughout the Straight Cliffs Formation. The