Ute quadrangle – two new maps

Map 177–Geologic map of the Ute quadrangle, Clark County, Nevada, by Craig M. dePolo and Wanda J. Taylor; 2012

M177

44 x 27.5 inches, color; 17-page text, b/w; folded or rolled, $23.00 ($18.00 for map only) or free on Web: http://www.nbmg.unr.edu/sales/pbsdtls.php?sku=M177

A 1:24,000-scale, color geologic map of the Ute 7.5-minute quadrangle in Clark County, Nevada with descriptions of 59 geologic units and 2 cross sections. Accompanying text includes full unit descriptions and references. GIS zip file also available online.

The Ute quadrangle covers the central part of the California Wash basin and a small section of the westernmost North Muddy Mountains, where Paleozoic and Mesozoic rocks were highly deformed by the Sevier orogeny. Tertiary and Quaternary sedimentary rocks record the history of basin filling and dissection. Noteworthy on the quadrangle are several resistant Quaternary petrocalcic surfaces, with as much as Stage VI carbonate development, that form pediment caps on the Tertiary basin deposits. The map includes the northern part of the Holocene-active California Wash fault and the southernmost part of the Quaternary-active Hogan Spring fault.

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Open-File Report 12-4–Preliminary erosional impact potential map of the Ute quadrangle, Clark County, Nevada, by Craig M. dePolo and Irene M. Seelye, 2012

of124

20.5 x 32.5 inches, color, scale 1:24,000; folded or rolled, $14.00 or free on Web: http://www.nbmg.unr.edu/sales/pbsdtls.php?sku=OF12-%204

There is a wide range of erosional susceptibility associated with different geologic units on the Ute quadrangle that might be considered when planning cross-country motor vehicle events, which are common in this valley. Tracks from motor races that can be seen in 1976 photography were hard to find in 2011 if they were on the harder petrocalcic surfaces, but caused long-lasting disruption of softer geologic units and surfaces with desert pavements on them. When more easily erodible units are disrupted, there is enhanced erosion from water runoff and significantly more dust is generated until the surface is stabilized with a new pavement, vegetation, or erodes down to a resistant layer. Using the distribution of the geologic units and their general erosional susceptibility, this Preliminary Erosional Impact Potential Map of the Ute Quadrangle was produced. This map can be used to plan race routes with the least erosional impact.

There are three general categories on the map:

1) more resistant units with lower erosional impact,

2) softer units that can be disrupted and eroded relatively easily, and

3) stream channels that have their surfaces refreshed when the channel flows with water.

The more resistant units include petrocalcic surfaces and pre-Tertiary limestones. Softer units include Tertiary basin sediments and Quaternary surfaces with pavements and an underlying loose silty layer. Stream channels are areas that have water flowing annually to every decade or so and have the ability to refresh themselves and recover from the effects of vehicular traffic. The map is experimental and is a simple derivative map from the Geologic Map of the Ute Quadrangle (NBMG Map 177).

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