Integrating Mineral and Groundwater Isotopic and Geochemical Analysis for Attribution of Salinity Sources and Aquifer Flow-Path Architecture in the Mesilla Basin, USA
Abstract
Spatial variability in sources of groundwater salinity may exist due to stratigraphic, geochemical, and hydrologic processes even in an integrated and relatively homogeneous aquifer system. Thus, characterization methods are needed to determine salinity sources and flow and transport pathways in groundwater systems. Isotopic and geochemical analyses from subsurface geologic formation samples and groundwater samples were compared to determine the sources of groundwater salinity and flow-path architecture of the Mesilla basin located in southern New Mexico and west Texas. Results from southern Mesilla basin groundwaters showed a localized plume of saline groundwater (10-30 g/L total dissolved solids). δ34S signatures of groundwater within the plume (+12.36 to +12.46‰) were comparable to δ34S signatures of Pennsylvanian-Permian gypsum (+12.5‰) suggesting evaporate mineral dissolution attributed to prolonged contact between groundwater and underlying Paleozoic bedrock deposits. To the north and upgradient, decreasing groundwater salinity coexisted with a spatial transition from sedimentary to volcanic rock underlying the alluvial aquifer, increasing alluvial sediment thickness, and δ34S signatures of groundwater (+2.28 to +5.76‰), which eliminates a direct Paleozoic source. These results indicate decreased upward flow from older sources and/or increased dilution of brackish groundwater inputs from depth within the lower salinity alluvial aquifer in the central and northern Mesilla Valley. This study illustrates how integrating mineral and groundwater isotopic and geochemical analyses support elucidation of sources of groundwater salinity and evaluation of heterogeneous aquifer flow-path architecture.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H53J1895C
- Keywords:
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- 1804 Catchment;
- HYDROLOGY;
- 1832 Groundwater transport;
- HYDROLOGY;
- 1879 Watershed;
- HYDROLOGY