DO CLASTIC SEDIMENTS IN ONE CAVE CONDUIT REFLECT BASIN-WIDE PALEOENVIRONMENTAL CONDITIONS?

We investigated the depositional patterns of clastic cave sediments in four caves in Greenbrier and Monroe Counties of West Virginia to test whether deposits found in a single karst conduit are representative of basin-wide or regional paleoenvironmental conditions. If no other variables obscure such signals, conduits that were hydrologically active during the same time should retain similar sedimentary records, documenting terrestrial paleoenvironmental conditions. While numerous sediment studies have been conducted in caves, no study has verified or challenged the assumption that sediments accurately record previous environmental conditions for a given region.  Caves were selected on the basis of proximity to each other, similar geology, presence of discrete input to long conduits, and apparently similar ages.  Within the cave systems there is limited stacking of passages, reducing the complexity of sediment deposition. Stratigraphic columns were constructed in the field and samples were collected for sediment (grain size, lithology), environmental magnetic (x_lf, x_fd, ARM, IRM), and paleomagnetic analyses. Magnetic particles behave differently given the environmental condition, so in essence, environmental magnetism provides a proxy for paleoenvironment.  Due to erosion and depositional complexities it was a challenge to find complete sedimentary sections.  Sediment analyses indicated that samples ranged in size from clay to cobbles and many samples analyzed for paleomagnetism showed normal polarity.  Taken in context with the landscape, this suggests that the conduits have been active for less than ~1Ma.  Catchment areas are underfit to conduit dimensions, which is expected as surface drainages evolve and become pirated to other conduits.  Some samples analyzed for environmental magnetic parameters demonstrated high magnetic susceptibility, corresponding to warmer periods by increased production of magnetic minerals due to soil-forming processes occurring outside of the caves.  A clear relationship existed between different passages in the same cave, but correlating became more difficult for passages in different drainage basins.  While sediments may be used for regional paleoclimate correlation, the best results were obtained when using magnetic variability for basin-wide correlations.