LIDAR AND FIELD-BASED SURFICIAL GEOLOGY AND GEOMORPHOLOGY MAPPING OF BLUESTONE NATIONAL SCENIC RIVER AND PIPESTEM STATE PARK, SOUTHERN WEST VIRGINIA

LiDAR-based "bare earth" DEMS and slope-shade maps were used to guide field work and surficial geology mapping in the Bluestone National Scenic River and adjacent portions of Pipestem State Park. Local bedrock is dominated by gently dipping shale, siltstone, sandstone, conglomerate and limestone of the Mississippian Mauch Chunk Group, lithologies that have yielded a complex variety of surficial deposits and landforms. Bluestone River has carved a steep canyon with over 350 m of local relief. Floodplains are of modest extent in the narrow valleys of the Bluestone and it largest tributaries, and are marked by numerous secondary high-flow channels. LiDAR reveals low terraces have significantly less dissected surfaces, even though they may be inundated during extreme floods. High-terrace deposits contain well-rounded alluvial cobbles and boulders, including quartz sandstones from headwaters Pennsylvanian strata; high-terrace clasts tend to be more weathered with increased distance above modern drainage. Most exposures of high-terrace alluvium lie buried under colluvium, and colluviated terraces and slip-off terraces are very difficult to differentiate from colluvial landforms on LiDAR imagery. LiDAR DEMS are very noisy for bouldery deposits of mixed colluvial and alluvial origins in low-order tributary valleys that drain resistant sandstone. Bouldery surfaces in many of these low-order valleys show significant incision: some of which appears to be ongoing. The most widespread surficial geology map units are steep “smooth” colluvial aprons and very steep “ribbed” colluvial-residual veneers. Bedrock cliffs are common within veneer map units. Upland benches are loosely associated with resistant sandstone layers, particularly the Princeton Sandstone, although bench regolith ranges from deeply weathered reddish-yellow shaley residuum to yellow-brown colluvial diamicton derived from adjacent slopes; the yellow-brown colluvium lies above the residuum in several poor outcrops. Residual soils on moderate relief uplands generally reflect underlying bedrock.