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Vermilion Cliffs National Monument Paria Canyon/Vermilion Cliffs Wilderness Paria Canyon Permit Area - Geology |
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Around Lees Ferry, the Triassic Chinle and Moenkopi Formations are exposed. The Chinle Formation consists of pink and reddish-purple sandstone; gray and green shale; and purple beds of volcanic ash with a dark brown conglomerate at its base. The Moenkopi Formation is the oldest formation exposed in Paria Canyon. It consists of dark reddish brown siltstone and mudstone. These formations were deposited in lake, braided stream and mud flat environments. The Paria River and its tributaries are located on the Colorado Plateau, an uplifted region of nearly-horizontal sedimentary rock. The Paria Canyon drainage system is bounded by the East Kaibab monocline or Cockscomb on the west and the Echo Cliffs monocline on the east near Lees Ferry. The Cockscomb folds and faults the formations down to the east while the Echo Cliffs monocline bends down to the west. This created the Paria Plateau/Marble Platform as a separate plateau within the Colorado Plateau.
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The Jurassic Navajo Sandstone is 1200 feet thick in Paria Canyon and is the most prominent formation. It is composed of crossbedded eolian sandstone deposited over millions of years as huge sand dunes migrated across a large desert broken only by an occasional oasis. Where the Paria River and Buckskin Gulch have cut through the Navajo Sandstone, slot canyons have formed. The Navajo Sandstone is very resistant in this desert environment and forms sheer cliffs and conical hoodoos.
