SURFICIAL GEOLOGY OF A WHITEWATER TREASURE - THE GAULEY RIVER NATIONAL RECREATION AREA, WEST VIRGINIA

The Gauley River National Recreation Area (GARI) is dominated by numerous medium to coarse blocks, up to 20 m in width, derived from the Nuttall or Raleigh sandstones in the New River Formation. Gauley River falls ~200 m in 45 km in GARI, whereas tributary Meadow River falls > 150 m in its lowermost 10 km. Together these rivers have incised a rugged, 100 to 300 m deep gorge into Pennsylvanian-aged New River and Kanawha formations. GARI’s > 100 rapids are diverse, formed by colluvial blocks, large landslides or bedrock outcrops. At least 6 are rated class V rapids, highlights of one of the world’s premier whitewater rivers.

Channel boulders 1-2 m in diameter are mobilized by common floods. Even-larger boulders and blocks litter river channels and most flood-prone areas, including steep toe slopes. Most are transported rarely, but the very largest are lag. Bouldery floodplains occur along < 10 % of the gorge; the few coarse alluvial fans are limited to larger tributary mouths. Terrace alluvium is uncommon, except inside Koontz Bend where a flight of terraces occurs up to 60 m above Gauley River. Soils on the highest terrace are deeply weathered, indicative of a rare stable surface in an otherwise highly dynamic landscape.

Colluvial blankets and aprons are widespread: the result of coalesced debris slides, boulder-block streams and other slope deposits. Open framework talus is locally developed and a cold-air producing talus was instrumented after temperatures >10˚C below ambient were measured in August 2010. Valley walls include many 15-25 m high sandstone cliffs and long slopes exceeding 70 %. The surficial geology of these slopes is a complex intermingled pattern of colluvial boulder diamicton, shallow residuum and rock outcrops. Debris-flow tracks occur on some of the highest and steepest slopes. Cliffs or deep sandy soils formed in upper Nuttall Sandstone dominate the gorge rim. Residuum formed in Kanawha shale and siltstone give rise to relatively flat uplands above the gorge. Kanawha sandstones cap dissected ridges rising > 100 m above the flat uplands.