SEDIMENT DEPOSITION PROCESSES IN CAVE ECOSYSTEMS: CASE STUDY IN WATER SINKS CAVE HIGHLAND COUNTY, VA

The sediment composition within caves provides valuable insights into water flow patterns during different stages of cave development. In this study, we examined the physical and geochemical properties of sediments in Water Sinks Cave, Highland County, Virginia, to reconstruct its sediment deposition history and developmental processes. A key objective was determining whether sediment accumulation is autochthonous or allochthonous and assessing the role of aluminosilicates embedded in the carbonate matrix. We collected 37 sediment samples from an unstudied sediment pile in an upper passageway of the cave and analyzed particle size, soil organic carbon content, and chemical composition. Five samples from outside the cave were also collected for comparison. Using a LiDAR scanner, a 3D cave model was generated to trace potential sediment transport pathways. Particle size analysis revealed that most interior samples were predominantly silt, with smaller proportions of clay and sand. Higher sand and lower silt concentrations were observed at shallower depths. Similarly, exterior samples were primarily silt but exhibited higher sand content. Soil organic carbon analysis showed a slight increase with depth in cave samples, whereas outside samples displayed a decrease with depth. These findings suggest the cave’s sediment pile is likely formed from multiple influx episodes, as indicated by particle size similarities between interior and exterior sediments. The increase in organic carbon in deeper cave sediments supports the hypothesis that older deposits are externally sourced, while younger sediments may represent in situ deposits. Ongoing X-ray diffraction (XRD) analysis aims to determine the mineralogy of silt- and clay-sized fractions. Preliminary XRD results indicate quartz as the dominant mineral, followed by orthoclase feldspar, mica, and minor amounts of kaolinite and calcite (<10% by mass). The mineralogy suggests that chert, derived from the limestone matrix, is the primary sediment source, highlighting an autochthonous origin.