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Yucca Mountain was designated as the proposed high-level radioactive waste repository by the U.S. Government in 1987. The proposed repository design requires high safety for a long maintenance period of 10,000 years. To satisfy this requirement, evaluation of the influence of earthquakes on the repository is necessary. Prediction of earthquake-induced ground motions around the repository requires knowledge of the dynamic properties of the geologic materials around the repository. The main geologic materials in the vicinity of Yucca Mountain are tuffs (ignimbrites) which are formed by the deposition of volcanic ash mixed with erupted volcanic gas, water vapor and pyroclastic material. Two types of dynamic tests, (1) the free-free, unconfined, resonant column and direct arrival test (freefree URC test) and (2) the fixed-free resonant column and torsional shear test (fixed-free RCTS test), were used to measure the dynamic properties of tuffs. The emphasis in this dynamic testing was evaluation of shear modulus (G) and material damping ratio (D) of the tuffs in the small-strain (linear) and mildly nonlinear (to strains of about 0.02 %) ranges. To evaluate the influence of various parameters on G and D of tuffs, correlations with other features such as total unit weight, porosity and stratigraphic unit were performed and general relationships between them are proposed. In addition, an unconfined, slow-cyclic torsional shear (CTS) device was developed and used to measure the cyclic shear properties of the tuffs from Yucca Mountain at larger strain amplitudes than possible in the fixed-free RCTS tests. Additionally, the CTS device was also used to determine the shear failure strength of the tuffs. By combining the cyclic shear properties of the tuffs from the CTS tests and the dynamic properties of the tuffs from the fixed-free RCTS tests, complete dynamic property curves from small-strain to failure strain were evaluated.

This dissertation is an attempt to give a picture of the Nevada frontier journalist Samuel L. Clemens and the surroundings in which he worked. It is also an assessment of the extent to which Clemens (and his alter ego Twain) can be considered a serious journalist and the extent to which he violated the very principles he championed.

New brachiopod materials from the lower Cambrian (Global Stage 3 and lower Stage 4) of Esmeralda County, Nevada are described and their age distribution and diversity is discussed. The specimens originate from the Fritzaspis, “Fallotaspis”, “Nevadella” and Bonnia-Olenellus biozone which in the area correspond to the Campito Formation and the overlying Poleta Formation. As the specimens from the Gold Coin Member (Begadean Series) and the Montenegro Member (Waucoban Series) of the Campito Formation encompass the oldest samples, they were therefore prioritised as there was not enough time to describe all the specimens. The oldest known trilobites from Laurentia have previously been reported from the Gold Coin Member and it is of interest to determine if the brachiopods from the same member also are the oldest known from Laurentia.As many specimens are poorly preserved, especially the ones from coarse siliciclastic intervals, the determination of their systematic position is somewhat aggravated. Despite this, a diverse fauna including Lingulida, Obolellida, Naukatida, Kutorginida, Orthida and stem-group brachiopods have been successfully identified. A total of 16 taxa were noted for the Campito fauna, including the problematic and rare genera Swantonia and Spinulothele but unfortunately little new information could be gained regarding the characters for these rare genera. Four genera are reported for the first time from the area, not including material described under open nomenclature. / Under den geologiska tidsåldern Kambrium (542-488 miljoner år sedan) uppträder de första fossilerna av djurgruppen brachiopoder, eller armfotingar som de också kallas, tillsammans med många andra djurgrupper. Få platser i Laurentia (paleo-kontinent bestående av nutidens Nordamerika och Grönland) finns kvar som har bevarat de tidigaste förekommande brachiopod fossilerna. Esmeralda län i Nevada är en sådan plats och det här har det även spekulerats att Laurentias absolut äldsta brachiopod fossil skulle kunna hittas där. Denna avhandling fokuserar på att studera dessa brachiopod fossil från Nevada. När åldern för de äldsta studerade brachiopoderna (Begadean I ålder) i denna avhandling jämfördes med tidigare dokumenterade åldrar för äldre lägre Kambrium brachiopod fossiler stod det klart att dessa är de äldsta brachiopod fossilerna som hittats hittills.Många nya fossil prover har samlats in av J.S. Hollingsworth under en längre tid från Nevada och beskrivs häri. De nya fossilen innefattar både sällsynta släkten, så som Swantonia samt Spinulothele, och släkten som inte har hittats i Esmeralda län tidigare. Tyvärr erhölls lite ny information beträffande de sällsynta släktenas morfologiska egenskaper. Upptäkterna om de nya släkterna i området skulle kunna hjälpa oss att bättre kunna rekonstruera brachiopod faunan från Nevada samt att förstå spridningen av olika brachiopod grupper i framtiden.

The Reno-Sparks community is in a seismically hazardous area. Recent research indicates that a Richter 7.0 or greater magnitude earthquake could affect the area. Many of the emergency and essential facilities are situated in dangerous geological locations and are housed in outdated structures which could be severely damaged in the event of a major earthquake. Detailed site evaluations need to be made with respect to location of new structures and of existing building safety. The 1979 Unified Building Code seismic provisions should be adopted without exception; Nevada Revised Statute 278 .160 needs to be revised to require a seismic safety plan; Alquist-Priolo legislation should be implemented, and creation of a comprehensive civil defense plan for seismic hazards is essential.

Seasonally snow covered alpine areas play a larger role in the hydrologic cycle than their area would indicate. Their ecosystems may be sensitive indicators of climatic and atmospheric change. Assessing the hydrologic and bio- geochemical responses of these areas to changes in inputs of water, chemicals and energy should be based on a detailed understanding of watershed processes. This dissertation discusses the development and testing of a model capable of predicting watershed hydrologic and hydrochemical responses to these changes. The model computes integrated water and chemical balances for watersheds with unlimited numbers of terrestrial, stream, and lake subunits, each of which may have a unique, variable snow -covered area. Model capabilities include 1) tracking of chemical inputs from precipitation, dry deposition, snowmelt, mineral weathering, basefiow or flows from areas external to the modeled watershed, and user -defined sources and sinks, 2) tracking water and chemical movements in the canopy, snowpack, soil litter, multiple soil layers, streamflow, between terrestrial subunits (surface and subsurface movement), and within lakes (2 layers), 3) chemical speciation, including free and total soluble species, precipitates, exchange complexes, and acid -neutralizing capacity, 4) nitrogen reactions, 5) a snowmelt optimization procedure capable of exactly matching observed watershed outflows, and 6) modeling riparian areas. Two years of data were available for fitting and comparing observed and modeled output. To the extent possible, model parameters are set based on physical or chemical measurements, leaving only a few fitted parameters. The effects of snowmelt rate, rate of chemical elution from the snowpack, nitrogen reactions, mineral weathering, and flow routing on modeled outputs are examined.

Seasonally snow covered alpine areas play a larger role in the hydrologic cycle than their area would indicate. Their ecosystems may be sensitive indicators of climatic and atmospheric change. Assessing the hydrologic and bio-geochemical responses of these areas to changes in inputs of water, chemicals and energy should be based on a detailed understanding of watershed processes. This dissertation discusses the development and testing of a model capable of predicting watershed hydrologic and hydrochemical responses to these changes. The model computes integrated water and chemical balances for watersheds with unlimited numbers of terrestrial, stream, and lake subunits, each of which may have a unique, variable snow-covered area. Model capabilities include (1) tracking of chemical inputs from precipitation, dry deposition, snowmelt, mineral weathering, baseflow or flows from areas external to the modeled watershed, and user-defined sources and sinks, (2) tracking water and chemical movements in the canopy, snowpack, soil litter, multiple soil layers, streamflow, between terrestrial subunits (surface and subsurface movement), and within lakes (2 layers), (3) chemical speciation, including free and total soluble species, precipitates, exchange complexes, and acid-neutralizing capacity, (4) nitrogen reactions, (5) a snowmelt optimization procedure capable of exactly matching observed watershed outflows, and (6) modeling riparian areas. Two years of data were available for fitting and comparing observed and modeled output. To the extent possible, model parameters are set based on physical or chemical measurements, leaving only a few fitted parameters. Thc effects of snowmelt rate, rate of chemical elution from the snowpack, nitrogen reactions, mineral weathering, and flow routing on modeled outputs are examined.

Master of Science / Department of Geology / Matthew Brueseke / The Little Goose Creek area is located in Elko County, Nevada just south of the central Snake River Plain and in the northeastern Great Basin. During the Miocene, northeastern Nevada was characterized by volcanism as well as prevalent extension and basin development, including widespread occurrences of porphyritic quartz-phyric silicic lavas and domes (e.g., the Jarbidge Rhyolite), ash-flow tuffs, and basaltic volcanism. Recent workers (e.g., Colgan and Henry, 2010) have provided new constraints on the timing of extension in the northern Great Basin (U.S.A.) and indicate that much of it occurred in the mid-Miocene. Other recent work has provided new temporal and petrologic constraints on 16.1 to 15.0 Ma Jarbidge Rhyolite volcanism in the northern Great Basin west of our study area, and suggest that it is intimately linked (spatially and temporally) with the aforementioned extension. This study aims to: [1] understand the spatiotemporal link between the volcanism in the northeastern Nevada study area and potentially correlative volcanism regionally (e.g., Jarbidge Rhyolite and explosive deposits associated with the <13 Ma Bruneau-Jarbidge or Twin Falls eruptive centers); [2] determine if the sampled Jarbidge Rhyolite lavas are chemically similar to those in and around Jarbidge, Nevada. In the Goose Creek area, we report a new laser [superscript]40Ar/[superscript]39Ar age for sanidine of 13.6 ± 0.03 Ma for a crystal-poor rhyolite lava (Rock Springs Rhyolite) and a Jarbidge Rhyolite lava (13.827±0.021 Ma) as well as an age on Jarbidge Rhyolite in Wells, NV (15.249±0.040 Ma) and West Wendover, NV (13.686±0.034 Ma). These lava samples, as well as sampled ash-flow tuffs from the Goose Creek region, plot within the A-type field on discrimination diagrams. The ash-flow tuffs are younger than the Rock Springs Rhyolite based on stratigraphic relationships and are sourced from both the Twin Falls eruptive center as well as the Bruneau Jarbidge eruptive center of the central Snake River Plain based on geochemical analysis. Also, a sequence of basaltic lavas crop out in the Goose Creek drainage; these basalts have ~43 wt.% silica and are chemically similar to <8 Ma olivine tholeiite basalts that crop out to the north, along the southwestern side of the Cassia Mountains, Idaho. These results, field relationships, and prior geological mapping suggest that the lavas and ash-flow tuffs erupted into active extensional basins.

No description available.

No description available.