Introduction Evaluation Prospects



Cougar Point Tuff
Jenny Creek Tuff
Harmony Hills Tuff
Condor Canyon
Leach Canyon Tuff
Tuff of Clipper Gap
Tuff of White Blotch Spring
Bates Mountain Tuff
Tuff of Lunar Cuesta
Shingle Pass Tuff








Miocene ignimbrites, although widespread, are not as voluminous as the Oligocene ash-flow tuff sheets that blanket most of the evaluation area. The Great Basin is in fact the largest ignimbrite province in the world. The Miocene ignimbrites with regional distribution and significance are described individually and in some detail below.

Many units of lesser extent, as well as those commonly undifferentiated in mapping, are not described in detail because of their limited and/or undefined distribution. These include the Tuff of Orange Lichen Creek, Tuff of Buckskin Point, Tuff of Buckwheat Rim, Tuff of Black Beauty Mesa, Tuff of Big Sand Springs, Tuff of Stuben Knob, Tuff of Reveille Range, Tuff of Arrowhead, and Tuff of Bald Mountain in the Pancake, Reveille and Hot Creek Ranges (Snyder and others, 1972; Ekren and Dixon, 1972), the tuff of Quinn Canyon Range in the Quinn Canyon Range (Ekren and others, 1977), the Tuff of Saulsbury Wash, Tuffs of Hanapah, and Tuff of McKinney Tanks in the southern Monitor Range (Kleinhampl and Ziony, 1985), and the tuffs of Meadow Creek in the Toiyabe and Toquima Ranges (Kleinhampl and Ziony, 1985). In Elko County the local Miocene tuffs include the Danger Point Tuff and Tuff of Wall Creek in the Jarbidge and Owyhee Quadrangles (Coats, 1964; 1971).

In northwestern Elko County unnamed pyroxene dacite welded and vitric tuffs are exposed in several areas including the Milligan Creek area in T. 40 N., R. 46 E., near Wilson Reservoir, and in the Owyhee and Mountain City Quadrangles (Coats, 1971, 1985). Near Milligan Creek the upper portion of the tuff is light brown and devitrified, with gas cavities and planar partings, and the lower portion is gray to black, dense vitric welded tuff with abundant augite and pigeonite phenocrysts (Coats, 1985). Although the unit is only about 20 feet thick it is exposed over a fairly large area. In the Wilson Creek area, the unit is composed of welded tuff overlain by air-fall and welded tuff of dacitic composition. In the Owyhee and Mountain City Quadrangles this unit is composed of thin densely welded tuff and coarse-grained welded lapilli tuff with clinopyroxene, plagioclase and anorthoclase, and has been dated at 15.3 to 16.8 Ma (Coats, 1985).

Ignimbrites with significant distribution are described in the following sections. These ash-flow tuffs are discussed and listed in generally increasing age or from youngest to oldest.

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Last modified: 09/12/06