VALLEY OF FIRE

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GEOLOGY

NEVADA U.S.A

 

South of Valley Of Fire is the Muddy Mountains where the Cretaceous Sevier fold-and-thrust belt is located which is apart of the larger system of structural deformation, the Cordilleran orogenic belt which runs from Guatemala to Alaska. 

The section of the Cordilleran Orogenic Belt located in Chihuahua and extends to southern Nevada, there have been doubts that the section is continuous because it's much harder to identify. The area has experienced pre-organic tectonic movement and post-organic movement, this has changed the rock deformation styles and made finding evidence of the Cordilleran Orogenic Belt more difficult. 

Valley Of Fire is also located within the Sevier Thrust Belt, the Thrusting Zone is rather narrow and not very deep. Faults in the Nevada section are considered thin-skinned and are also related to folds in Utah. The Sevier Thrust Belt extends into Canada and Mexico although the southern Arizona and the northern Mexico section are not very well understood. 

 

Valley of Fire is located in the large Basin And Range Province which extends into Washington State and as far south as Mexico.  

 

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Rock Layers

The main Rock Layers in the Valley Of Fire are comprised of Aztec Sandstone, but other layers are visible from within the park most notably the Muddy Mountains Visible to the south. 

 

The layers in the Muddy Mountains are cut drastically just after the Jurassic Aztec Sandstone as that's where the Great Unconformity is located, all above strata has been weathered away before the placement of the Miocene aged Overton Conglomerate member of the Baseline Sandstone (Name Changed from Overton Fanglomerate). 

AZTEC SANDSTONE

The Aztec Sandstone is fine to medium-grained and contains up to 8% feldspar and is classed as subarkose which means the rock matrix is less than 15% mud matrix and between 5%-25% of the grains are feldspar. The individual grains are subrounded to rounded, the grains are indented from the compression of the eolian desert environment. The pore space in between grains is filled with clay cement predominantly kaolinite and a lesser-mix of illite-smectite. 

The red colours in the upper and lower Aztec Sandstone units are formed from thin grains coated in hematite, other colours like purple, yellow, orange and white are the result of iron oxide, hydroxide cement, and the dominant pigments being formed from hematite and goethite.

   

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ELEPHANT ROCK

Elephant Rock is formed from the exploitation of joints and splay faults within the Aztec Sandstone by weathering and erosion, the area is heavily faulted as smaller faults form from larger ones which is how splay faults are created. Elephant Rock is most likely formed from jointing in the sandstone itself rather than faulting. 

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WEATHERING & EROSION

Weathering and Erosion is responsible for the formation of windows, arches, spires and fins within Valley Of Fire.

MUDDY MOUNTAIN OVERTHRUST

The Muddy Mountain Overthrust is the southern end of an imbricated thrust sheet that extends as far north as the Canadian Rockies, the Muddy Mountain thrust sheet is tilted with the Lake and Gass Peak thrust sheets around the same area. The Overthrust is visible by the dark Paleozoic carbonate limestone and dolomite rocks of the Bonanza King Formation which overlies the Aztec Sandstone to the south.

The Muddy Mountain Overthrust extends from the Clark Mountains in California to the Muddy Mountains Nevada and is 210 Kilometres long, the thrust sheet moved from west to east. The thrust sheet moved over an erosional surface (forethrust debris), and is offset by the Las Vegas Shear Zone. 

The Las Vegas Shear Zone is located in the Las Vegas Valley which is filled with tertiary and quaternary sedimentary rocks underlain by alluvial deposits, the only volcanic rocks are visible in the south of the valley. The volcanics erupted between 21-12 million years ago in the Miocene epoch. The shear zone has offset North-South trending mountain ranges and has bent ranges into cross-folded structures along with offset structural trends and boundaries around Las Vegas. 

 

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FAULTS

There are lots of faults in Valley of fire but only one is currently still active when entering the state park, that is the California Wash Fault which is visible from the south entering Valley of Fire Highway from Las Vegas. The fault is technically not in the park at all but driving over it when entering from Las Vegas is unavoidable, the fault is noticeable as the abrupt rising Muddy Mountain's are slightly behind it.

   

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The Muddy Mountains behind the California Wash Fault, viewed from Valley Of Fire Highway

CALIFORNIA WASH FAULT

The Fault goes by two names, the Sevier Fault in Utah and the Toroweap Fault in Arizona. 

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CALIFORNIA WASH 

FAULT

REFEreNCES

HARALD DREWES; The Cordilleran orogenic belt between Nevada and Chihuahua . GSA Bulletin; 89 (5): 641–657.  

V.E. Langenheim, R.C. Jachens, and K.M. Schmidt PRELIMINARY LOCATION AND GEOMETRY OF THE LAS VEGAS VALLEY SHEAR ZONE BASED ON GRAVITY AND AEROMAGNETIC DATA U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY: This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Peter Eichhubl Texas A&M University-Corpus Cristi Texas, Eric Flodin Indiana University-Purdue University, Fort Wayne Indiana. Brittle Deformation, Fluid Flow, and Diagenesis in Sandstone at Valley of Fire State Pary, Nevada Geological Society Of America Field Guide 6, 2005 

Paul J. Umhoefer; L. Sue Beard; Melissa A. Lamb

Miocene Tectonics of the Lake Mead Region, Central Basin and Range

Geological Society of America 

Volume 463, June 01, 2010

R. Ernest Anderson U.S. Geological Survey, L. Sue Beard U.S. Geological Survey Geology of the Lake Mead region: An overview

The Geological Society of America Special Paper 463 2010