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 the western edge of the Cretaceous Western Interior Seaway. It is bounded below by the Tropic Shale and above by the Wahweap Formation. A variety of fossil species have been found within the Straight Cliffs including ammonites, mollusks, foraminifera, ostracods, sharks, fish, amphibians, turtles, lizards, crocodyliforms, dinosaurs, and mammals. The Straight Cliffs Formation overlies the Cenomanian-Turonian Tropic Shale Formation and underlies the Campanian Wahweap Formation. It preserves fluvial and marginal marine strata from the Kaiparowits Basin of the Cretaceous Western Interior Seaway. The formation is primarily composed of sandstone and has lesser amounts of siltstones, mudstones, coals, and conglomerates. It