A map of Zion with the stops that we made.

The nearly horizontal sedimentary bedrock exposed in Zion Canyon tells a fascinating tale of the evolution of the climate and land during the time of the rock layers deposition.  275 million years of strata are exposed in various points throughout the park.  The most prominent bedrock segment of the canyon is the Navajo Sandstone which comprises over 600 meters of cemented sand dunes with isolated paleo-oases.  The Navajo Sandstone is largely responsible for the dramatic cliffs that are exposed creating the Zion Canyon.  Middle Jurassic Limestone caps, of the Temple Cap and Carmel Formations, on the Navajo Sandstone create the spectacular, locally called, monoliths/temples of the canyon. The figures below briefly describe the bedrock geology and climatic sequences that formed the rock formations seen in Zion National Park.  A great way to view the entire bedrock sequence within the park is from watchman’s overlook.

Fluvial Geomorphology of Canyon Formation-  As the Colorado Plateau uplifted the stream gradient of the Virgin River was also increased.  This caused the river to gain velocity and increase its erosional capability.  The river removed almost all the Cretaceous sediment and rock and began to downcut into the Jurassic and Triassic sedimentary rock layers which includes the Navajo Sandstone.  Because of the bedrock constrictions the river was not able to migrate laterally as easily as it was able to downcut.  The downcutting progressed and carved the narrow canyon into the Navajo Sandstone that can be seen in the “Narrows” area.  Further downstream downcutting exposed the more erodeable layers of the Kayenta, Moenave, and Chinle formations allowing for relatively extensive lateral migration creating the wider canyon area at the canyon’s southern most section.  Tributary streams lacked the power to erode and downcut that the larger Virgin River had leaving hanging valleys high above the current river level.  These hanging valleys now provide spectacular waterfalls that flow over the tributary valleys boundary with the canyon.