Master of Science in Geoscience
First Committee Member
David K. Kreamer, Chair
Second Committee Member
Jean S. Cline
Third Committee Member
Kevin H. Johannesson
Graduate Faculty Representative
Vernon F. Hodge
Number of Pages
In the eastern Grand Canyon, secondary porosity created by north trending faults, folds, and breccia pipes, facilitates groundwater flow through the South Rim carbonate aquifer. Springs associated with the South Rim Aquifer have low 3H concentrations, [Ca2+]/[Mg2+] rations close to unity, and variable uranium concentrations. For a geochemical comparison, springs are subcategorized on the basis of geology and discharge. Type I springs are associated with high-angle normal faults and have high discharge rates. These springs discharge Ca2+ - Mg2+, HCO3- waters, have 3H concentrations <2 TR, and 234U/238U activity ratios >3 AR, which suggest long groundwater residence times. Type II and IV springs are located on canyon mesas and have low discharge rates. These springs are predominantly Ca2+ - Mg2+, SO42- waters, have tritium ratios between 1 and 6 TR, and 234U/238U activity ratios between 1 and 2 AR. Higher 3H and 238U concentrations and low 234U/238U activity ratios in the latter waters may be due to shorter groundwater residence time. Based on 3H concentration, the occurrence of dedolomitization, and the resultant uranium isotope fractionation in groundwater, the minimum residence time of water discharging from the South Rim Aquifer is indicated to be > 40 years.
Arizona – Grand Canyon; Aquifers; Groundwater flow; Groundwater recharge; Springs
Geochemistry | Hydrology
Fitzgerald, Jim, "Residence time of groundwater issuing from the South Rim Aquifer in the eastern Grand Canyon" (1996). UNLV Theses, Dissertations, Professional Papers, and Capstones. 1426.