Hydrogeology of desert springs in the Panamint Range, California,USA: Geologic controls on the geochemical kinetics, flowpaths, and mean residence times of springs

Abstract

Over 180 springs emerge in the Panamint Range near Death Valley National Park, CA, yet, these springs have received very little hydrogeological attention despite their cultural, historical, and ecological importance. Here, we address the following questions: (1) which rock units support groundwater flow to springs in the Panamint Range, (2) what are the geochemical kinetics of these aquifers, and (3) and what are the residence times of these springs? All springs are at least partly supported by recharge in and flow through dolomitic units, namely, the Noonday Dolomite, Kingston Peak Formation, and Johnnie Formation. Thus, the geochemical composition of springs can largely be explained by dedolomitization: the dissolution of dolomite and gypsum with concurrent precipitation of calcite. However, interactions with hydrothermal deposits have likely influenced the geochemical composition of Thorndike Spring, Uppermost Spring, Hanaupah Canyon springs, and Trail Canyon springs. Faults are important controls on spring emergence. Seventeen of twenty‐one sampled springs emerge at faults (13 emerge at low‐angle detachment faults). On the eastern side of the Panamint Range, springs emerge where low‐angle faults intersect nearly vertical Late Proterozoic, Cambrian, and Ordovician sedimentary units. These geologic units are not present on the western side of the Panamint Range. Instead, springs on the west side emerge where low‐angle faults intersect Cenozoic breccias and fanglomerates. Mean residence times of springs range from 33 (±30) to 1,829 (±613) years. A total of 11 springs have relatively short mean residence times less than 500 years, whereas seven springs have mean residence times greater than 1,000 years. We infer that the Panamint Range springs are extremely vulnerable to climate change due to their dependence on local recharge, disconnection from regional groundwater flow (Death Valley Regional Flow System ‐ DVRFS), and relatively short mean residence times as compared with springs that are supported by the DVRFS (e.g., springs in Ash Meadows National Wildlife Refuge). In fact, four springs were not flowing during this campaign, yet they were flowing in the 1990s and 2000s.

Synecological response of spring benthic prokaryotes and macroinvertebrates to Paleozoic roof pendant‐derived calcium

“…Because TracerLPM minimizes error as it seeks a solution within the specified boundaries, the analytical error reported for each water sample by the lab was used to assess numerical uncertainty in the model. The results from TracerLPM were compared with residence times calculated using a recharge‐weighted, steady‐state, backward‐in‐time tritium mixing model (Gleason et al, 2020) to identify discrepancies in residence times. The raw data, analytical uncertainty, estimated residence time, and numerical uncertainty associated with 3 H dating are reported in data tables 1 and 3 archived at https://doi.org/10.5281/zenodo.7603891.…”

“…Finally, a chlorine‐36 chronometer ( 36 Cl/Cl chronometer) was utilized to estimate the residence times of spring water samples that were not suitable for either 3 H or 14 C dating (Gleason et al, 2020). The 36 Cl/Cl chronometer was produced by fitting a trend line between the 36 Cl/Cl ratio and the contributing groundwater residence time of springs that had young residence times (estimated using 3 H) and springs that had old residence times (estimated using 14 C).…”

“…An envelope of uncertainty surrounds the chronometer since there is analytical uncertainty in the measured 3 H and 36 Cl/Cl compositions of the spring water and numerical uncertainty in the estimation of 3 H and 14 C residence times. Uncertainty in the 36 Cl/Cl chronometer residence times was determined by linearizing the trend line (Gleason et al, 2020). The raw data, analytical uncertainty, estimated residence time, and numerical uncertainty associated with 36 Cl dating are reported in data tables 1 and 3 archived at https://doi.org/10.5281/zenodo.7603891.…”

“…Spring waters were dated using a sequential approach using 3 H, 14 C, and 36 Cl in that order (Gleason et al, 2020). First, 3 H dating was used to identify the youngest spring waters (e.g., the shortest residence times).…”