GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 106-3
Presentation Time: 9:00 AM-6:30 PM

GEOLOGIC CONTROLS ON GROUNDWATER FLOWPATHS IN THE SPRING MOUNTAINS, NV INFERRED FROM SPRING WATER GEOCHEMISTRY AND 87SR/86SR


WARIX, Sara R.1, RADEMACHER, Laura K.2, MEYERS, Zachary P.3, FRISBEE, Marty D.3, GLEASON, Carolyn L.3, HEDLUND, Brian P.4, FRIEL, Ariel D.4 and PORDEL, Khaled5, (1)Department of Geosciences, Idaho State University, 921 S. 8th Avenue, Pocatello, ID 83209, (2)Dept of Geological and Environmental Sciences, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, (3)Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, (4)School of Life Sciences and Nevada Institute of Personalized Medicine, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV 89154-4004, (5)Natural Resource and Environmental Science, University of Nevada Reno, 1664 N. Virginia Street, Fleischmann Agriculture, Room 217, Reno, NV 89557

We seek to better understand the geologic controls on groundwater flow and geochemical evolution in the Spring Mountains, NV using geochemistry, 87Sr/86Sr, and variations in flowpath geology. This combination of analyses can provide insights into flowpaths in regions with complex topographic and structural features such as in the Spring Mountains. Understanding groundwater quality and flow in arid regions like the southern Great Basin is important as groundwater springs are commonly the primary source of perennially available fresh water to riparian ecosystems. Furthermore, desert communities often rely on groundwater for their drinking water supply, as surface water is scarce. Recharge in the Spring Mountains contributes to groundwater flow locally as well as regionally to the Death Valley regional groundwater flow system (DVRFS). Groundwater flow in the Spring Mountains is controlled by north to northeast-trending thrust faults, which serve as possible conduits for deep groundwater to discharge at the land-surface.

Variability in groundwater source areas is evident from analysis of spring water geochemistry and 87Sr/86Sr. Geochemical indicators, including Mg/Ca and 87Sr/86Sr of spring waters, correlate to three main water types: 1) limestone and dolomite dominated springs emerging in the central Spring Mountains, with 87Sr/86Sr ranging from 0.708-0.711 and a Mg/Ca between 0.5-1.0; 2) dolomite dominated springs along the Keystone Thrust with Mg/Ca (>1.0) and 87Sr/86Sr (>0.710); and 3) siliciclastic dominated springs, with sulfate concentrations >0.001 mol/L and 87Sr/86Sr >0.730. Rocks specimens representing units along potential groundwater flowpaths were also collected and underwent leaching experiments. 87Sr/86Sr results for leachates are pending and will further constrain spring water source areas and flow paths. Results from this study provide insight into the importance of structural features in controlling groundwater flowpaths as spring geochemistry can be often be predicted by the location of the spring emergence relative to large thrust faults.