Hydrogeochemical Evolution of Groundwaters in the Williston Basin, Canada
Glacial cycles over the last two million years have successfully altered deep groundwater flow in the Williston Basin, Canada. Mixing with evaporated paleoseawater has resulted in unique geochemical signatures in formation waters with spatial and temporal trends, however the timing of glaciogenic recharge into the Williston Basin and spatial understanding of the flow system is loosely constrained. I examine timing and effect of glaciogenic recharge by using an integration of fluid chemistry, stable isotope data, and transport modeling. Results demonstrate that meltwater arrived at depths of ~600 to 1000 m in the northcentral region of the Williston Basin at two separate time periods, 75 to 150 ka and 300 ka. Spatial analysis of geochemical data illustrates that meltwater recharge extended to a continuous recharge belt along the northern margin of the Williston Basin, greater than previously anticipated. Individual and multi-variate analysis of isotope and solute geochemistry exhibit trends that contribute to fractionation of δ18O, δ2H, 87Sr/86Sr, δ37Cl, and δ81Br, and validates the importance of water origin and variation in mineral composition on solute concentrations and isotope values. Although overprinting and mixing interactions may present challenges in geochemical interpretation, the inter-disciplinary approach used in this research contributes to a greater understanding of how glacial meltwater recharge altered geochemical landscapes during large-scale salt dissolution in the Williston Basin.
Master of Science (M.Sc.)