CHARACTERIZATION OF STRONTIUM ISOTOPES IN GROUNDWATER IN THE DEEP RIVER TRIASSIC BASIN, NORTH CAROLINA

Increased concern about the impacts of hydraulic fracturing on groundwater quality has created a need for research in this area. However, a lack of data on baseline water quality parameters has made this work difficult. This study characterizes strontium (Sr) isotopes of groundwater in the methane-bearing Sanford sub-basin of North Carolina and tests the efficacy of ⁸⁷Sr/⁸⁶Sr as a groundwater tracer in this region before such drilling takes place. Strontium isotopic ratios in the study area were found to have a narrow range (0.7116 ±0.001), suggesting that Sr could be a sensitive tracer of future groundwater movement or contamination. Two groundwater populations were found: a more radiogenic group (0.7119±0.0006) as well as a group with lower isotopic ratios (0.7092±0.0002) Strontium isotopes were not found to be correlated to other geochemical parameters tested (major ions, trace metals, isotopes of C, H and O). Although Sr isotopes were not correlated to surface geology they are correlated to latitude and proximity to exposures of the Cumnock Formation. The spatial patterns seen suggest that Sr isotopic composition of groundwater in the Sanford sub-basin may be controlled by the occurrence of the Cumnock Formation at the surface and in the shallow subsurface.