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Zion Visitor Center
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Stop 30 Zion National Park Visitor Center
Location: About 26 miles northwest of Kanab, UT.
Date: March 12, 2007

Located in Southwestern Utah, Zion Canyon is one of the most stunning landforms in the world.  It’s one a series of spectacular canyons that were created largely in response to uplift of the Colorado Plateau.  Located at the western margin of the Colorado Plateau and Basin and Range Province, Zion provides a fascinating look into 275 million of year of sedimentary strata.  Zion also lies on a major structural block in-between two major south-southwest trending normal faults which step down to the Basin and Range Province.  The Hurricane Fault (west side) and Sevier Fault (east side) serve as the boundary of this structural block.  The canyon itself is over 15 miles long and 800 meters deep carved out by the North Fork of the Virgin River.

 


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.

 


Formation of Zion National Park

 

Yeah

Rock Layer

Appearance

Where To See

Deposition

Rock Type

Photo

Dakota Formation

Cliffs

Top of Horse Ranch Mountain

Streams

Conglomerate and sandstone

Dakota Sandstone

Carmel Formation

Cliffs

Mt.Carmel Jct.

Shallow sea and coastal desert

Limestone, sandstone and gypsum

Carmel Formation

Temple Cap Formation

Cliffs

Top of West Temple

Desert

Sandstone

Temple Cap Formation atop Navajo Sandstone

Navajo Sandstone

Steep cliffs 1,600 to 2,200 ft (490 to 670 m) thick
Red lower layers are colored by iron oxides

Tall cliffs of Zion Canyon; highest exposure is West Temple. Cross-bedding shows well at Checkerboard Mesa

Desert sand dunes covered 150,000 mile² (390,000 km²)
Shifting winds during deposition created cross-bedding

Sandstone

Navajo Sandstone showing its two tones

Kayenta Formation

Rocky slopes

Throughout canyon

Streams

Siltstone and sandstone

Kayenta Formation

Moenave Formation

Slopes and ledges

Lower red cliffs seen from Zion Human History Museum

Streams and ponds

Siltstone and sandstone

Moenave Formation

Chinle Formation

Purpleish slopes

Above Rockville

Streams

Shale, loose clay and conglomerate

Chinle Formation

Moenkopi Formation

Chocolate cliffs with white bands

Rocky slopes from Virgin to Rockville

Shallow sea

Shale, siltstone, sandstone, mudstone, and limestone

Moenkopi Formation

Kaibab Formation

Cliffs

Hurricane Cliffs along I-15 near Kolob Canyons

Shallow sea

Limestone

Hurricane Cliffs/Kaibab Fm.

 

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.

 

 

 

By Phillip Larson