Testing the 14C ages and conservative behavior of dissolved 14C in a carbonate aquifer in Yucca Flat, Nevada (USA), using 36Cl from groundwater and packrat middens

Kwicklis, Edward; Farnham, Irene

doi:10.1007/s10040-014-1131-3

Cited by 3 publications

(3 citation statements)

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“…The validity of such an assumption necessitates that dissolved inorganic carbon migration rates approximate groundwater flow rates. This appears to be a reasonable approximation; dissolved inorganic carbon has been shown to move at a similar pace to chloride, a conservative tracer (see Kwicklis & Farnham, ).…”

Section: Isotope Hydrogeologymentioning

confidence: 88%

Global Isotope Hydrogeology―Review

Jasechko

2019

Reviews of Geophysics

218

124

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Groundwater 18O/16O, 2H/1H, 13C/12C, 3H, and 14C data can help quantify molecular movements and chemical reactions governing groundwater recharge, quality, storage, flow, and discharge. Here, commonly applied approaches to isotopic data analysis are reviewed, involving groundwater recharge seasonality, recharge elevations, groundwater ages, paleoclimate conditions, and groundwater discharge. Reviewed works confirm and quantify long held tenets: (i) that recharge derives disproportionately from wet season and winter precipitation; (ii) that modern groundwaters comprise little global groundwater; (iii) that “fossil” (>12,000‐year‐old) groundwaters dominate global aquifer storage; (iv) that fossil groundwaters capture late‐Pleistocene climate conditions; (v) that surface‐borne contaminants are more common in younger groundwaters; and (vi) that groundwater discharges generate substantial streamflow. Groundwater isotope data are disproportionately common to midlatitudes and sedimentary basins equipped for irrigated agriculture, but less plentiful across high latitudes, hyperarid deserts, and equatorial rainforests. Some of these underexplored aquifer systems may be suitable targets for future field testing.

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Section: Isotope Hydrogeologymentioning

confidence: 88%

Global Isotope Hydrogeology―Review

Jasechko

2019

Reviews of Geophysics

218

124

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“…Figure 15 shows that in volcanic rocks at Pahute Mesa, the 36 Cl/Cl ratio is relatively constant across a wide range of Cl concentrations and generally similar to the estimated presentday 36 Cl/Cl ratios in NNSS-area precipitation of 490 × 10 −15 (Fabryka-Martin et al 1993). Figure 15 can be compared with similar plots of 36 Cl/Cl versus 1/Cl for groundwater from the lower carbonate aquifer (LCA) shown in Moran and Rose (2003) and Kwicklis and Farnham (2014). The 36 Cl/Cl versus 1/Cl plots in those studies showed a decrease in 36 Cl/Cl ratios with decreasing 1/Cl (or increasing Cl concentrations), which indicated that the mineral source of the higher Cl samples from the LCA had little or no 36 Cl.…”

Section: Chloridementioning

confidence: 78%

“…Evidence of 36 Cl/Cl deposition from packrat middens and reconstruction of meteoric 36 Cl/Cl deposition near the NNSS indicates that 36 Cl/Cl ratios in precipitation have varied by a factor of as much as two over the past 40,000 years (Fig. 16; Plummer et al 1997;Kwicklis and Farnham 2014). As indicated by Fig.…”

Section: Chloridementioning

confidence: 93%

Understanding long-term groundwater flow at Pahute Mesa and vicinity, Nevada National Security Site, USA, from naturally occurring geochemical and isotopic tracers

et al. 2021

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Recently collected naturally occurring geochemical and isotopic groundwater tracers were combined with historic data from the Pahute Mesa area of the Nevada National Security Site (NNSS), Nevada, USA, to provide insights into long-term regional groundwater flow patterns, mixing and recharge. Pahute Mesa was the site of 85 nuclear detonations between 1965 and 1992, many of them deeply buried devices that introduced radionuclides directly into groundwater. The dataset examined included major ions and field measurements, stable isotopes of hydrogen (δ2H), oxygen (δ18O), carbon (δ13C) and sulfur (δ34S), and radioisotopes of carbon (14C) and chloride (36Cl). Analysis of the patterns of groundwater 14C data and the δ2H and δ18O signatures indicates that groundwater recharge is predominantly of Pleistocene age, except for a few localized areas near major ephemeral drainages. Steep gradients in sulfate (SO4) and chloride (Cl) define a region near the western edge of the NNSS where high-concentration groundwater flowing south from north of the NNSS merges with dilute groundwater flowing west from eastern Pahute Mesa in a mixing zone that coincides with a groundwater trough associated with major faults. The 36Cl/Cl and δ34S data suggest that the source of the high Cl and SO4 in the groundwater was a now-dry, pluvial-age playa lake north of the NNSS. Patterns of groundwater flow indicated by the combined data sets show that groundwater is flowing around the northwest margin of the now extinct Timber Mountain Caldera Complex toward regional discharge areas in Oasis Valley.

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