Paper No. 9
Presentation Time: 3:35 PM


FLOREA, Lee J., Department of Geological Sciences, Ball State University, 2000 W. University Ave, Muncie, IN 47306, DUGAN, Chelsie R., Geological Sciences, Ball State University, Muncie, IN 47306, WYNN, Jonathan G., Department of Geology, University of South Florida, 4202 E. Fowler Avenue, SCA 528, Tampa, FL 33620 and MCKINNEY, Cami, Department of Interior, National Park Service, Timpanogos Cave National Monument, American Fork, UT 84003,

This abstract focuses upon δ18O and δ2H of water samples collected in 2012 from cave pools and the American Fork River within Timpanogos Cave National Monument (TICA) in Utah. Samples from nearby Cascade Springs, a karst spring mantled with glacial till, and two thermal springs near Midway provide comparison with active groundwater flow systems. In the cave pools of TICA, there is clear clustering before June with a higher average Dex. After June, the isotopic composition of the samples trends toward more negative values of δ2H and progresses below the Global Meteoric Water Line. It is possible that these trends represent a change from reservoirs dominated by melt waters to reservoirs progressively influenced by waters with significantly lower Dex, perhaps by evaporative fractionation.

The American Fork River has the most negative δ18O, consistent with water derived from snowmelt at elevations above 2,900m. Samples at the same elevation from cave pools in TICA cluster at different locations on a LWL, suggesting source waters at differing elevations. The average δ18O in Cavern of Sleep is the least negative, suggesting a source at the elevation of the cave—2,025m. The average δ18O in Hidden Lake and Middle Lake are more negative than Cavern of Sleep, perhaps from water infiltrating the epikarst above the cave—2,195m and 2,121m, respectively. Hansen Lake has the lowest average δ18O in TICA, suggesting the canyon rim as the source—2,440m. Isotope data from Soda Pop Pit shift from a composition similar to Hansen Lake before June toward values similar to Middle Lake after June. This implies a change in source-water from the canyon rim to the overlying epikarst. A regression between δ18O and proposed source elevations gives an altitude lapse rate of 0.4‰ 100m-1 along the Wasatch Front. Using this lapse rate, the δ18O data from Cascade Springs and the thermal springs in Midway suggest source elevations between 2,800 and 3,100 m or 18O depletion from orographic rainout.