Hydrogeology of the Great Basin region of Nevada, Utah, and adjacent states
ABSTRACT The many geologic formations and rock types found in the Great Basin can be grouped into 12 major hydrogeologic units on the basis of lithology, areal extent, and water-bearing characteristics. The units range in age from Precambrian through Holocene, and represent metamorphic rocks, carbonate and clastic sedimentary rocks of both marine and continental origin, and plutonic and volcanic rocks. Regional aquifers are comprised of basin-fill deposits in all parts of the Great Basin, Paleozoic carbonate rocks (limestone and dolomite) in the eastern Great Basin, and possibly Tertiary and Quaternary volcanic rocks in some parts of the Great Basin.
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ABSTRACT: Arsenic and selenium concentrations along with the major solutes were measured in ground-waters sampled from springs in Pahranagat Valley and Ash Meadows, Nevada, Death Valley, California, and from wells from the Nevada Test Site and Yucca Mountain, Nevada. The multivariate statistical technique correspondence analysis was applied to the data to determine relationships between the groundwaters from these areas, the aquifer materials and the As and Se concentrations, and to examine the relationships between As and Se and the other chemical parameters included in the statistical analysis. The correspondence analysis indicates that a strong relationship exists between chloride and Se in the groundwaters and that As is not associated with chloride. The strong association between chloride and Se suggests that Se behaves more conservatively than As in these oxygenated, circumneutral pH groundwaters. No strong association was observed between the As and/or Se concentrations of the groundwaters and the aquifer material with which these waters interact (i.e. regional Paleozoic carbonate aquifer, Tertiary tuffaceous volcanic rocks, and/or basin-fill deposits). However, it is likely that sampling of groundwaters from the various aquifers was insufficient to determine relationships between the aquifer materials and groundwater chemistry. Associations were observed between the groundwaters of the Nevada Test Site and Yucca Mountain regions and the groundwaters of the regional carbonate aquifer that discharge at Ash Meadows and Death Valley, suggesting mixing of these waters. Ground-water from the regional carbonate aquifer in Pahranagat Valley, which is upgradient from the Nevada Test Site, Yucca Mountain, Ash Meadows, and Death Valley, exhibited no association with groundwaters from these regions.Journal of Hydrology 04/1996; 178(1-4):181-204. DOI:10.1016/0022-1694(95)02804-8
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ABSTRACT: Groundwater samples were collected from 11 springs in Ash Meadows National Wildlife Refuge in southern Nevada and seven springs from Death Valley National Park in eastern California. Concentrations of the major cations (Ca, Mg, Na and K) and 45 trace elements were determined in these groundwater samples. The resultant data were subjected to evaluation via the multivariate statistical technique principal components analysis (PCA), to investigate the chemical relationships between the Ash Meadows and Death Valley spring waters, to evaluate whether the results of the PCA support those of previous hydrogeological and isotopic studies and to determine if PCA can be used to help delineate potential groundwater flow patterns based on the chemical compositions of groundwaters. The results of the PCA indicated that groundwaters from the regional Paleozoic carbonate aquifers (all of the Ash Meadows springs and four springs from the Furnace Creek region of Death Valley) exhibited strong statistical associations, whereas other Death Valley groundwaters were chemically different. The results of the PCA support earlier studies, where potentiometric head levels, δ18O and δD, geological relationships and rare earth element data were used to evaluate groundwater flow, which suggest groundwater flows from Ash Meadows to the Furnace Creek springs in Death Valley. The PCA suggests that Furnace Creek groundwaters are moderately concentrated Ash Meadows groundwater, reflecting longer aquifer residence times for the Furnace Creek groundwaters. Moreover, PCA indicates that groundwater may flow from springs in the region surrounding Scotty's Castle in Death Valley National Park, to a spring discharging on the valley floor. The study indicates that PCA may provide rapid and relatively cost-effective methods to assess possible groundwater flow regimes in systems that have not been previously investigated. Copyright © 1999 John Wiley & Sons, Ltd.Hydrological Processes 12/1999; 13:2655-2673. DOI:10.1002/(SICI)1099-1085(19991215)13:17<2655::AID-HYP840>3.0.CO;2-4
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ABSTRACT: Samples collected from springs and wells in southern Nevada were analyzed for major solutes and trace elements as part of a larger study to characterize the geochemical signatures of these groundwaters. In this study, principal component analysis (PCA) was used to reduce the large data sets, including the four major cations (Ca, Mg, Na, K) and 27 trace elements, analyzed in these groundwater samples. Principal components analysis of the major cation data indicates that groundwaters from Cenozoic felsic volcanic rock aquifers/aquitards of southern Nevada exhibit strong chemical associations to each other but weak relationships to groundwaters from the regional carbonate aquifer (which were instead chemically similar to each other). However, PCA of the trace element data demonstrates that some groundwaters from the volcanic aquifers/aquitards are chemically similar to those of the underlying regional carbonate aquifer. The PCA also reveals that these groundwaters from the volcanic aquifers/aquitards have significantly different trace element compositions than perched groundwaters contained within similar felsic volcanic rocks. Moreover, rare earth element (REE) data from groundwaters collected from wells finished in the volcanic aquifers/aquitards of southern Nevada have similar concentrations and similar shale-normalized patterns to the carbonate aquifer groundwaters as well as local carbonate rocks. These same southern Nevada well waters do not exhibit REE concentrations or shale-normalized signatures that resemble the perched volcanic groundwaters or the tuffs of southern Nevada. The REE data and trace element PCA, along with previous carbon isotope analyses, water temperature data, hydraulic head relations, and results of a recent pump test of a well near Yucca Mountain, suggest close contact of the regional carbonate groundwaters and groundwaters from the overlying volcanic rocks of southern Nevada and possible upwelling of the carbonate groundwaters into the overlying volcanic rock units in the vicinity of Yucca Mountain.Journal of Hydrology 03/2001; DOI:10.1016/S0022-1694(00)00418-2