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
Brazos River tributaries of the Upper Brazos that rise on the high plains of the Llano Estacado, flowing southeast through the center of Texas. Another major tributary of the Upper Brazos is the Clear Fork Brazos River, which passes by Abilene and joins the main river near Graham. Important tributaries of the Lower Brazos include the Paluxy River, the Bosque River, the Little River, Yegua Creek, the Nolan River, the Leon River, the San Gabriel River, the Lampasas River, and the Navasota River. Initially running east towards Dallas-Fort Worth, the Brazos turns south, passing through Waco and the Baylor University campus, further