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Source-linked reports with geographic coverage including Nevada.

At least 1,171 records · Page 65Linked to original sources
USGS1969

An analysis of gravity data in Area 12, Nevada Test Site

The gravity data available from Healey and Miller (1963a) were augmented by new observations along three profiles through two new drill holes in Area 12; UEI2t #1 and UEI2p #1. The data were interpreted to allow evaluation of the geologic structure prior to the planning and excavation of two proposed tunnel complexes, Ul2t and Ul2p. Density values for each of six rock units were determined to allow a two-dimensional analysis of the gravity data along the above-mentioned profiles. The surficial rocks of Quaternary and Tertiary age and the Tertiary volcanic rocks have a weighted average density of 1.86 gm/cc. The density of the caprock at Rainier and Aqueduct Mesas ranges from 2.17 gm/cc at UEI2p #1 to 2.27 gm/cc at UEI2t #1. The Gold Meadows stock and the associated Precambrian quartzite have an arithmetic average density of 2.60 gm/cc for all samples measured. The middle Paleozoic dolomite in Area 12 has an arithmetic average density of 2.75 gm/cc. The clastic rocks of Paleozoic age have an arithmetic average density of 2.60 gm/cc. Interpretation of the residual gravity data indicates a maximum thickness of about 2,800 feet for all Tertiary volcanic rocks. A normal fault striking N. 30 ? E. disrupts the pre-Cenozoic surface at UEI2p #1 and 0.4 mile east of UEI2t #1. The throw within rock of Paleozoic age is about 400-500 feet. Another normal fault that strikes about N. 20 ? E. is located about 1.5 miles east of UEI2p #1. The throw of this fault is at least 1,100 feet in rocks of pre-Cenozoic age. Elevation contours representing the pre-Cenozoic surface in Area 12 show a maximum relief of about 2,000 feet.

Nevada↗
USGS1969

Summary of geologic effects of the Boxcar event, Nevada Test Site

A high-yield underground nuclear explosion at the U20i site, formed a sink 1,000 feet in diameter above the explosion point. Fractures opened as far as 20,000 feet from the explosion and rock-falls occurred as far as 15 miles. Most fractures were coincidental with north-trending naturally occurring faults. Maximum displacement along a fault was 3 feet vertically with the downthrown side the same as that on the original fault.

Nevada↗
USGS1968

Hypogene veins of gibbsite, pyrolusite, and lithiophorite in Nye County, Nevada

Gibbsite, lithiophorite, pyrolusite, and goethite, plus discrete mixtures of gibbsite and lithiophorite and of gibbsite and iron oxide, occur as replacement veins in limestone. Minor accessories are barite, alunite, opal. Minerals of wall-rock alteration are garnet, idocrase, K-feldspar, prehnite, sericite, and quartz. These silicates formed at higher temperature than the vein minerals, but the whole sequence is considered to be a product of the same solutions, of deep-seated origin, deposited over a long period of time.

Nevada↗
USGS1968

The circle creek rhyolite, a volcanic complex in northern Elko county, Nevada

The Circle Creek Rhyolite is a multiple-source mass of fayalite-ferro-augite rhyolite, forming an extensive complex in northern Elko County, Nevada, with a diameter of about 8 miles and an exposed area of about 36 square miles. From the structure of the flow layering and the complex sequence of microbrecciation structures, it seems to be a relatively thick mass that rose passively through many fissures to flood a sag basin in the older rocks, which are as young as the early Pliocene Idavada Volcanics, a sequence of ignimbrites and tuffs. Chemical analyses, thin-sections, and X-ray diffractometer studies show that the Circle Creek Rhyolite is a two-feldspar rhyolite. The interrelations of the pyroxene phases are unusually complex. The Circle Creek is partly concealed by later tuffs, gravels, and olivine basalt and is cut by two sequences of high-angle faults of different ages.

Nevada↗
USGS1968

Temperature data from exploratory boreholes at the Supplemental Test Site, central Nevada - interim report

In cooperation with the U.S. Atomic Energy Commission, the U.S. Geological Survey is making precise temperature measurements in exploratory boreholes at the Supplemental Test Site, central Nevada. Together with thermal properties measurements made on the core, and additional temperature measurements in progress these data will he used to estimate geothermal flu: from the area. The purpose of this interim report is to make our preliminary temperature measurements available to other interested groups. The locations of the sites are shown on figure 1, and data pertinent to the state of disequilibrium at the time of measurement are tabulated in table 1. In the geothermal profiles (figs. 2 through 13) the temperature is given in decrees centigrade and the depth (Z) in meters.

Nevada↗
USGS1968

Subsurface geology of the Silent Canyon caldera, Nevada Test Site, Nevada

Deep drilling in the vicinity of Silent Canyon on eastern Pahute Mesa, Nevada, has revealed a Tertiary volcanic section locally thicker than 14,000 feet. The area drilled covers most of the Silent Canyon caldera and some of the surrounding area. The caldera is rudely elliptical in plan and measures 10 by 14 miles. Except on its east edge, the caldera is completely obscured by younger volcanic rocks, including ash-flow sheets from several other centers. The structure, originally inferred from surface mapping and a 20-mgal gravity low, has been confirmed by drilling at 21 sites. Petrographic, chemical, and magnetic studies of more than 4,000 feet of drill core have revealed a complex sequence of volcanic rocks. Precaldera rocks include thick talc-alkalic lavas and tuffs. Peralkaline lavas and tuffs of the Silent Canyon center include the Belted Range Tuff (13-14 m.y.), eruption of which resulted in caldera collapse. The Belted Range Tuff has been downdropped 5,000-7,000 feet in the caldera. Subsequently, the depression was partially filled in the eastern part by genetically related peralkaline lavas and tuffs and in the western part by later calc -alkaline lavas and tuffs apparently genetically unrelated to the peralkaline rocks of the Silent Canyon center. Renewed subsidence probably occurred during their eruption. Isopach maps of younger tuffs show that the caldera was topographically low during deposition of later (12.5-7 m.y.) ash-flow sheets from other volcanic centers.

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