12. Geochemistry of cave pools connected to an alpine epikarst—Timpanogos Cave National Monument, Utah
Published:January 01, 2016
Lee J. Florea, Chelsie R. Dugan, Camille McKinney, 2016. "12. Geochemistry of cave pools connected to an alpine epikarst—Timpanogos Cave National Monument, Utah", Caves and Karst Across Time, Joshua M. Feinberg, Yongli Gao, E. Calvin Alexander, Jr.
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Weekly water samples collected in the spring and summer of 2012 demonstrate the dynamic geochemistry within the epikarst of an alpine karst aquifer in Timpanogos Cave National Monument in the Wasatch Mountains near Salt Lake City, Utah, USA. The results of chemical analysis of water from four cave pools, supplemented with concurrent samples from the American Fork River, suggest three modes of recharge: (1) diffuse recharge through the permeable matrix of the carbonate rock, (2) rapid recharge through open fractures in the epikarst, and (3) rapid recharge via piston flow through fractures occluded with colluvium.
Water levels in the cave pools recharged by diffuse flow were very stable during the study period. Elevated dissolved solids characterized the geochemistry, including solutes associated with hydrothermal activity in this region (e.g., SO4 2− and F−). Isotopes of sulfur and carbon, along with cation-anion ratios suggest that sulfide oxidation may play some role in modern dissolution of the carbonate bedrock. In situ geochemical reactions influence the concentration of some solutes (e.g., HCO3 −, Ca2+, F−) and may cause a shift in the isotopes of dissolved inorganic carbon.
Water levels in the cave pools characterized by rapid recharge, in comparison, were highly variable. When the flow path was direct, the geochemistry of the pool was strongly influenced by the timing and rate of recharge. During times of limited recharge, the geochemistry of these pools evolved toward the values of pools dominated by diffuse flow. On the other hand, when the flow path was impeded by colluvium, recharge was stored, and the geochemical signal was homogenized. In both cases, the source of recharge may be from elevations substantially above the cave pool.