SEARCHING FOR THE SOURCE: GEOCHEMICAL EVIDENCE FOR THE SOURCE OF THE WATER THAT DEPOSITS THE SNOWY RIVER CALCITE WITHIN THE FORT STANTON-SNOWY RIVER CAVE SYSTEM, LINCOLN COUNTY, NM

The Fort Stanton-Snowy River Cave, located in the eastern foothills of the Sierra Blanca Mountains in south central New Mexico, is entirely developed within the Rio Bonito Member of the Permian San Andres Formation. This formation consists of limestone and dolostone with minor gypsum beds. The Snowy River deposit is a unique calcite deposit that resembles a white riverbed within the cave. This deposit has been mapped to over 12 cave miles in length, making it one of the longest speleothems in the world. Because of its unique and delicate nature, its preservation is of great importance to cave and natural resource managers. However, the source of the super-saturated water that deposits the calcite is unknown. Flooding of the Snowy River portion of the cave has been roughly correlated to large precipitation and run-off events within the local watershed. Three small creeks in the area, Rio Bonito, Little Creek, and Eagle Creek, have been hypothesized as possible sources of water to the cave. To understand if these creeks contribute to subsurface water, major and trace elements as well as isotopes of water and strontium were analyzed in both surface waters and groundwater. To compare with the water samples, the same constituents were also analyzed from local rock samples and cores from the Snow River calcite deposit. Geochemical analyses of the waters suggest that cave waters are similar in composition to Rio Bonito and Eagle Creek water and nearby groundwater, and dissimilar to Little Creek water. Analyses of the rock samples and cores show similarities between the calcite core samples and the limestone collected from the lowest member of the San Andres Formation. These results indicate that, as it enters the subsurface, surface waters from Eagle Creek and Rio Bonito mix with the regional groundwater, likely within a sub-surface reservoir contained in the Rio Bonito Member of the San Andres Formation. From there, the mixed and super-saturated water eventually enters the paleo-channel within the cave and deposits the Snowy River calcite.