Tag Archive for: MIllard County
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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.
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.
A 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.