SEDIMENT CHARACTERIZATION FOR FUTURE COSMOGENIC DATING IN RACCOON MOUNTAIN CAVERNS, HAMILTON COUNTY, TN

We investigated sediments contained in Raccoon Mountain Caverns to assess the feasibility of applying cosmogenic nuclide (²⁶Al/¹⁰Be) dating to understand incision rates and timing of cave formation. The cave system formed within the Monteagle Limestone below quartz-rich Pennsylvanian sandstones and conglomerates of the Cumberland Plateau. We examined cave sediments with signs of fluvial (through-channel) deposition for quartz grains and gravels sourced from the Pennsylvanian sandstones transported into the cave from surface streams. Sediments that contained rounded and imbricated clasts were sampled at 5 locations: 3 at different levels within the cave, 1 from the stream bed in the lowest level of the cave, and 1 from the bed of a surface stream leading into the cave. The coarse fraction (>2 mm) of each sample was measured and the lithology/mineralogy of the clast was identified. The fine fraction was analyzed with the hydrometer method and was characterized with XRD and petrographic microscopy. Quartz was identified in the clay fraction with XRD, visually in the sand (in thin section), and as pebbles and quartz sandstone fragments in the coarse fraction. The gravels of the surface and stream caves contained over 80% quartz pebble and quartz sandstone fragments. In the cave sediments, 33-39% percent of the sand fraction and 39-84% of the gravel fraction contained quartz. The quartz pebbles and grains found in the cave sediments are comparable to those observed in the surface and cave streams. Initial findings indicate that quartz sands and gravels derived from the sandstones and conglomerates outside the cave and subsequently deposited within the cave may be used for future dating applications. The channel deposits within Raccoon Mountain Caverns may hold a record of the incision rate and development of local and regional streams linked to the Tennessee River at that location. Future dating techniques will be applied to these sediments as funding becomes available. Dates obtained with cosmogenic nuclides will be used to compare the development of this cave system with others in the region and along the Cumberland Plateau.