Tag Archive for: MIllard County

Spring-fed Pruess Lake, Snake Valley, Millard County, Utah.
Photographer: Matt Affolter

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Cambrian Fossils in Utah’s West Desert, Millard County

Utah is recognized for having the longest and most diverse dinosaur record in the nation. Yet, the Cambrian rocks in Utah’s West Desert contain one of our nation’s best records of the early evolution of life on Earth. View a slideshow of rocks and fossils from the West Desert here. During the Cambrian Period, North America straddled the Equator and the continent was oriented nearly 90 degrees clockwise of its present position. The Cambrian coastline extended north-south across Utah shifting southward (our east) with rising sea level. This resulted in a nearly complete sequence of Cambrian rocks preserved in Utah’s West Desert on what was the northern coastline of early North America. When Tertiary extension forces formed the Basin and Range Geological Province throughout the last 20 million years, these Cambrian rocks became well-exposed across western and central Utah, revealing the extraordinary fossil record within. Nowhere is this geology better exposed than in Millard County, Utah. Refer to Hintze and Davis (2003) (17 MB PDF) for a detailed discussion of the county’s geology. The Cambrian is best known for the “Cambrian Explosion” (or “Cambrian Radiation”) , when a great diversity of multicellular animals first appears. The first scientific report on these fossils was a description of Elrathia kingii in 1860, probably the world’s most well-known trilobite species.

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Crystal Peak, Millard County, Utah
Photographer: Matt Affolter

Certain rock types weather into curious shapes and patterns by combinations of internal factors such as fractures and sediment grain size and external factors such as frost action and salt crystallization. Sandstone, granite, volcanic rocks, and limestone are all excellent mediums for creating bizarre rockscapes that can include smooth, rounded, and undulating forms (hoodoos or “goblins”), pinnacles, tafoni (holes and small alcoves), and honeycomb structures.

The Tunnel Spring Tuff exhibits remarkable tafoni (alcoves and pitting) covering the steep slope of Crystal Peak.

Cowboy Pass in the Confusion Range, Millard County, Utah
Photographer: Matt Affolter

Snow highlights rock layers in the Ely Limestone near Cowboy Pass in the Confusion Range, Millard County.

Many of the dry desert peaks of western Utah tell a story of shallow tropical seas. As much as 500 million years of deep burial, uplift, and erosion have changed layers of organic mud to cliffs and ledges of layered limestone. Closer inspection reveals abundant fossils, evidence of ancient sea life.

Notch Peak, House Range, Millard County, Utah
Photographer: Michael Vanden Berg

Abundant trilobite fossils, including  Elrathia kingi shown here, can be found  within the Wheeler Shale east of Notch Peak in the House Range.

Many of the dry desert peaks of western Utah tell a story of shallow tropical seas. As much as 500 million years of deep burial, uplift, and erosion have changed layers of organic mud to cliffs and ledges of layered limestone. Closer inspection reveals abundant fossils, evidence of ancient sea life.

Notch Peak National Natural Landmark, House Range, Millard County, Utah
Photographer: Matt Affolter

Cambrian- to Ordovician-aged carbonate rocks (limestone and dolomite) make up Notch Peak, where a 2,200-foot cliff (possibly the tallest carbonate cliff in North America) leads to a deep canyon on the west side of the peak. Pink, Jurassic-aged granite is exposed at the foot of the mountain, and scattered deposits of white, clayey marl deposited in Lake Bonneville during the late Pleistocene are present on the valley floor.

 

Trilobite, House Range, Millard County, Utah
Photographer: Michael Vanden Berg

Cambrian-age shales from western Utah’s House Range contain millions of fossilized trilobites, such as this specimen of Elrathia kingi.

The entrance to a cave, unofficially called “Beware Cave,” is marked by an overhang under which springs emerge at the deepest part of Gandy Warm Springs and Warm Creek—almost 4 feet deep. Gandy Warm Springs is a refreshing oasis of tiny waterfalls, pools, caves, and crystal clear streams with water temperatures up to 81 ̊F. Located on the western edge of Snake Valley, near the Nevada border, the springs are at the base of the southern tip of Spring Mountain (also called Gandy Mountain). The spring water that cascades down the slope of Spring Mountain joins a larger spring that emerges from a cave, initiating the eastward-flowing Warm Creek (also called Gandy Creek). Lush green vegetation,  including mosses, watercress, and bright green algae, and animals such as aquatic snails (including the endemic springsnail,Pyrgulopsis saxatilis, found only at Gandy) and the native speckled dace wonderfully stand in stark  contrast to the surrounding dry yellow grasses and desert shrubs. Gandy is a popular spot for locals who use the area for soaking, swimming, and baptisms.
The enormity and vastness of the cliff forming the north face of Notch Peak is difficult to describe. Standing near the cliff’s base and looking up is awe inspiring. The view while standing at the top and looking over the edge? I would not know as I was on my hands and knees, too fearful to stand and look over the edge at one of the greatest vertical drops in the contiguous U.S.
Reported estimates of the cliff’s actual height vary significantly from under 2,000 feet to over 4,500 feet, which is likely due to differences in defining where the base of the cliff starts. Photogrammetry (measurements from digital stereoscopic photographs), verified with a paper 7.5′ topographic map, suggests the cliff has an uninterrupted near-vertical drop of over 1,500feet. The addition of cliff below a small bench 50 to 100 yards wide increases the distance to approximately 2,250 feet. Adding a portion of the very steep base of the sheer drop  increases the distance to nearly 2,900 feet.

snake-valley-drillA new interactive map of Snake Valley with all of the well data, has recently been added to the Utah Geological Survey (UGS) Web site.  The West Desert Ground-Water Monitoring Network is almost complete and updates are available on a newly developed Google Earth™ interactive map.  The network will monitor ground water for more than 50 years in Snake Valley, western Millard County and adjacent areas.  The $3.5 million network is a response to planned ground-water development in east-central Nevada.  The Utah Geological Survey will upload data onto its Web site.

Objectives included: assessing the potential impacts of pumping on ground water and spring flow in Utah; evaluating flow patterns in the aquifer from Snake Valley to Fish Springs National Wildlife Refuge; determining baseline water-level and chemical trends in local and regional ground-water flow systems; and, measuring the capacity of the aquifers to transmit and store ground water.

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