Caves in Grand Canyon, Arizona, USA fall into two main categories: those formed under unconfined conditions and those formed under confined conditions. This study focuses on the hydrology and paleohydrology of the confined caves in the Redwall–Muav aquifer, where the aquifer is overlain by rocks of the Supai Group and underlain by the Bright Angel Shale. Unconfined caves are discussed only in their relation to confined caves. Discharge for confined groundwater was, as it is today, primarily from the Redwall Limestone where it has been incised by the main canyon or its tributaries and where it has converged along a structural low or fault. Descent of the potentiometric surface (or water table) over time is recorded by one ore episode and six cave episodes: (1) emplacement of Cu–U ore, (2) precipitation of iron oxide in cavities, (3) dissolution of cave passages, (4) precipitation of calcite-spar linings over cave passage walls, (5) precipitation of cave mammillary coatings, (6) minor replacement of cave wall and ceiling limestone by gypsum, and (7) deposition of subaerial speleothems. The mammillary episode records the approximate position of the water table when the incision of the canyon was at that level. Discharge toward spring points has reorganized and adjusted with respect to ongoing canyon and side-canyon incision. The dissolution of Grand Canyon confined caves was the result of the mixing of epigene waters with hypogene waters so that undersaturation with respect to calcite was achieved. The karst hydrology of Grand Canyon may be unique compared to other hypogene cave areas of the world.

Caves of the Guadalupe Mountains have experienced many modifications since their final phase of sulfuric acid speleogenesis several million years ago. Petrographic and geochemical data reveal details of the change from H2SO4 to CO2-dominated reactions. The H2SO4 dissolution front acquired a coating of replacement gypsum with local pockets of anhydrite and by-products of altered clay, including Fe-Mn oxides. Alteration of bedrock beneath the gypsum produced a white micritized rind with small negative shifts in δ13C and δ18O. Solution basins contain records of the earliest post-speleogenetic processes: corroded bedrock, residual anhydrite, Fe-Mn oxides from fluctuating pH and Eh, mammillary calcite, and dolomitization. Later meteoric water removed or recrystallized much of the gypsum and early micrite, and replaced some gypsum with calcite. Mammillary crusts demonstrate fluctuating groundwater, with calcite layers interrupted by films of Fe-Mn oxides precipitated during periodic inflow of anoxic water. Condensation moisture (from local evaporation) absorbs CO2 from cave air, corroding earlier features and lowering their δ13C and δ18O. Drips of condensation water deposit minerals mainly by evaporation, which increases δ18O in the speleothems while δ13C remains nearly constant. By forcing calcite precipitation, evaporation raises the Mg content of remaining water and subsequent precipitates. Dolomite (both primary and replacive) is abundant. In areas of low air circulation, water on and within carbonate speleothems equilibrates with cave-air CO2, causing minerals to recrystallize with glassy textures. Fluorite on young evaporative speleothems suggests a recent release of deep-source HF gas and absorption by droplets of condensation water. 

Uranium-series analyses of water-table-type speleothems from Glenwood Cavern and “cavelets” near the town of Glenwood Springs, Colorado, USA, yield incision rates of the Colorado River in Glenwood Canyon for the last ~1.4 My. The incision rates, calculated from dating cave mammillary and cave folia calcite situated 65 and 90 m above the Colorado River, are 174 ± 30 m/My for the last 0.46 My and 144 ± 30 m/My for the last 0.62 My, respectively. These are consistent with incision rates determined from nearby volcanic deposits. In contrast, δ 234U model ages (1.39 ± 0.25 My; 1.36 ± 0.25 My; and 1.72 ± 0.25 My) from three different samples of mammillary-like subaqueous crust collected from Glenwood Cavern, 375 m above the Colorado River, yield incision rates of 271 +58/-41 m/My, 277 +61/-42 m/ My, and 218 +36/-27 m/My. These data suggest a relatively fast incision rate between roughly 3 and 1 Ma. The onset of Pleistocene glaciation may have influenced this rate by increasing precipitation on the Colorado Plateau starting at 2.5 Ma. Slowing of incision just before 0.6 Ma could be related to the change in frequency of glacial cycles from 40 to 100 kyr in the middle Pleistocene. This interpretation would suggest that the cutting power of the Colorado River prior to 3 Ma was smaller. An alternative interpretation involving tectonic activity would invoke an episode of fast uplift in the Glenwood Canyon region from 3 to 1 Ma.