BATHERS CAVE REVISITED: CLIMATIC INTERPRETATION USING GEOCHEMISTRY, SEDIMENTOLOGY AND LUMINESCENCE DATING

Within Bathers Cave, Virginia, is a 50-100 cm thick clastic sediment package located 250 m from the entrance to the cave that includes 4 distinct layers: a lower rubbly yellow layer, a black, a red, and an upper laminated orange layer. Previous estimates using paleomagnetic evidence indicated an age within the topmost orange layer at the short-lived Blake event (114-119 ka) and the shift in geochemistry and sedimentology of the deposits correlated to the 128 ka 5e isotope boundary. The timing of deposition for this package within the cave is also supported by a denudation rate of the nearby Maury River of 150m/ma. In an effort to better constrain the timing of these depositional events, samples for optically stimulated luminescence dating (OSL) were collected from locations above and below the level of apparent climate shift. OSL dates from the orange layer above the apparent climate shift are 176ka, whereas an age of 65.1ka is derived from the yellow layer below the climate shift, indicating older material stratigraphically above sediment that is 100 k years younger. In order to better understand the dynamics of this apparent reversal of superposition, petrographic, mineralogical, and geochemical analyses were replicated on our previous samples above and below this apparent climate shift, and compared to new samples below our original study interval, which superficially duplicate the layering of yellow to black, to orange sediments seen higher in the cave deposits. The new samples lower in the section were deposited under flow conditions ranging from quiescent to turbulent, similar to our original package higher in the section. Clays of the upper and lower samples are mineralogically similar (having smectite, illite, kaolinite, quartz, and goethite), but differ in intensities and trends up section. Fe and Mn geochemistry show similar trends among the respective layers, yet differ in intensity in the top and lower sequence. Our results suggests that geomorphically higher and older cave passages were scoured of sediment that was subsequently deposited on top of sediments in a geomorphically lower and younger cave passage. Our OSL results may also suggest the need for multiple, single grain measurements, as bulk analyses may be contaminated by reworking.