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: a b s t r a c t Evidence of a multi-centennial scale dry period between w2800 and 1850 cal yr BP is documented by pollen, mollusks, diatoms, and sediment in spring sediments from Stonehouse Meadow in Spring Valley, eastern central Nevada, U.S. We refer to this period as the Late Holocene Dry Period. Based on sediment recovered, Stonehouse Meadow was either absent or severely restricted in size at w8000 cal yr BP. Beginning w7500 cal yr BP, the meadow became established and persisted to w3000 cal yr BP when it began to dry. Comparison of the timing of this late Holocene drought record to multiple records extending from the eastern Sierra Nevada across the central Great Basin to the Great Salt Lake support the interpretation that this dry period was regional. The beginning and ending dates vary among sites, but all sites record multiple centuries of dry climate between 2500 and 1900 cal yr BP. This duration makes it the longest persistent dry period within the late Holocene. In contrast, sites in the northern Great Basin record either no clear evidence of drought, or have wetter than average climate during this period, suggesting that the northern boundary between wet and dry climates may have been between about 40 and 42 N latitude. This dry in the southwest and wet in the northwest precipitation pattern across the Great Basin is supported by large-scale spatial climate pattern hypotheses involving ENSO, PDO, AMO, and the position of the Aleutian Low and North Pacific High, particularly during winter.Quaternary Science Reviews 08/2013; 78:266-282. · 4.57 Impact Factor
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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 01/2001; · 2.96 Impact Factor