Author ORCID Identifier
Year of Publication
Master of Science (MS)
Arts and Sciences
Earth and Environmental Sciences (Geology)
Dr. Benjamin W. Tobin
One of the most prominent features of the Grand Canyon is the iron-stained Redwall Limestone, which has been documented to contain extensive cave systems with significant storage potential in the karstic Redwall-Muav (R-M) aquifer. The hydrogeologic relationships between the R-M aquifer and cave formation in the Grand Canyon via descending (epigenic) surface waters have been well documented. However; the potentially large role of deeply sourced (hypogenic) waters rising from depth in relation to cave formation is poorly understood. The Bopper Cave System (BCS) is a relict feature of the ancient abandoned hydrologic system at Grand Canyon and displays unique network maze cave morphologies formed under phreatic conditions with rich and diverse mineral associations of allochthonous sediments. There are competing hypotheses on confined network maze cave development in the Grand Canyon, with observations supporting both epigenic and hypogenic processes. The nature of expansive phreatic passages, cupolas, solution pockets, and lack of vadose features suggest that the BCS was formed from hypogene speleogenesis. X-ray diffraction identifies vast amounts of speleogenetic gypsum deposits, other varieties of sulfates, and corrosion residue, all of which indicate that the dominant hypogene fluid was sulfuric acid-bearing. 𝛿34S values for gypsum flowers from Double Bopper range from 0.6‰ to -13.9‰ (VCDT), with an average of -6.4‰ (n=25). Sulfur isotopes identify three plausible sources of sulfuric acid in the Grand Canyon region including magmatic sulfur, sulfide oxidation from pyrite, and sulfide oxidation from hydrocarbons. Identifying sulfuric acid speleogenesis (SAS) and the ancient hydrogeologic conditions necessary for network maze cave development holds implications for better understanding the evolution and dynamics of the modern aquifer. Present-day hypogene speleogenesis may contribute to significant previously unrecognized mega-conduit storage capacity in the modern Redwall-Muav aquifer.
Digital Object Identifier (DOI)
National Speleological Society Northern Rocky Mountain Grotto Research Grant in 2022
National Speleological Society Ralph W. Stone Graduate Fellowship in Cave and Karst Studies in 2021
Geologic Society of America Jack Hess Karst Research Award in 2021
University of Kentucky, Earth and Environmental Sciences Ferm Fund in 2021
Heimel, Sierra, "Hypogene Speleogenesis in the Grand Canyon; Observational, Mineralogical, and Geochemical Investigations from the Bopper Cave System" (2023). Theses and Dissertations--Earth and Environmental Sciences. 97.