New Mexico Geological Society Annual Spring Meeting & Ft. Stanton Cave Conference — Abstracts

The Snowy River calcite deposit within the Fort Stanton-Snowy River Cave System is unique. The source of the water that creates this 12-mile-long speleothem is not well understood. One way to better understand this source is to determine where the cave lies stratigraphically within the Permian San Andres Limestone. In the Fort Stanton area, the San Andres Limestone has four members: the Glorieta Sandstone, the Rio Bonito Member, the Bonney Canyon Member, and the Fourmile Draw Member. In the study area, the oldest and most prominent member, and the one that the cave is likely developed within, is the Rio Bonito Member. This member consists of alternating thin and thick beds of limestone which are variably fossiliferous, vuggy, and dolomitized. Some beds of limestone contain nodules of extremely dense, sometimes siliceous limestone; the distinct morphology of these nodules makes them easily recognizable in the formation. These same nodules may be seen in the Snowy River Passage portion of the cave at Independence Hall, and the identification, if confirmed, will aid in correlation of the stratigraphy outside of the cave with that inside the cave. Correlating the stratigraphy is an important step in understanding where water may be infiltrating to the subsurface. Another important step to understanding the Fort Stanton Cave system is understanding the geomorphic history of the cave and the sediments within it. In the Snowy River Passage, remnant clastic sediments cover the walls and lie beneath the Snowy River calcite layer. Pebbles and crossbedding within those sediments suggest a higher depositional energy than what is present today. These observations suggest that there may have been a subterranean stream in the Snowy River Passage, prior to precipitation of the Snowy River calcite, which has been dated to be approximately 830 years old. Work beginning in summer of 2022 will distinguish depositional packages of sediment, characterize sediment, and collect samples for optically stimulated luminescence age-dating.