Uplift of the Colorado Plateaus and the opening of the Gulf of California by 5 mya changed the drainage of the Colorado River and its tributaries, including the Paria River, which is eroding headward between two plateaus adjacent to the park. The greater Bryce area was uplifted as part of the High Plateaus by the same forces. After Laramide mountain building came to an end, about 15 mya, a large part of western North America began to be stretched into the nearby Basin and Range topography. This event raised the Rocky Mountains far to the east and caused the retreat of the sea that covered the Bryce Canyon area. Other formations were also formed but were mostly eroded following uplift from the Laramide orogeny which started around 70 million years ago ( mya). The ancient depositional environment of the region around what is now Bryce Canyon National Park varied from the warm shallow sea (called the Cretaceous Seaway) in which the Dakota Sandstone and the Tropic Shale were deposited to the cool streams and lakes that contributed sediment to the colorful Claron Formation that dominates the park's amphitheaters. The exposed geology of the Bryce Canyon area in Utah shows a record of deposition that covers the last part of the Cretaceous Period and the first half of the Cenozoic era in that part of North America. The pink-colored cliffs, alcoves and amphitheaters along the eroding eastern face of the plateau expose the approximately 50-million-year-old Claron Formation. About 2 miles (3 km) away is the Paunsaugunt Fault a normal fault along which the Paria River valley is subsiding on one side while the Paunsaugunt Plateau rises on the other. Geology of the area in Utah Paria View overlooks an intermittent stream flowing toward the Paria River, some 8 miles (13 km) to the east.
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