MASS WASTING DEPOSITS ALONG THE BLUE RIDGE ESCARPMENT IN JONES GAP STATE PARK AND THE ROCKY BOTTOM, SOUTH CAROLINA AREAS

Prehistoric and modern mass wasting deposits and talus aprons are widespread along steep slopes bordering the Middle Saluda River (1200 ft local relief) in Jones Gap State Park, Greenville County, SC and near Rocky Bottom, Pickens County, SC. Six large mass wasting deposits, three in each of the two areas, are the focus of this study. The Mountain Bridge Area trail system provides access to deposits in the Jones Gap SP area. Individual deposits were outlined on maps using GPS coordinates. Margins were indentified by changes in density of boulders on the slope.

One deposit on the north slope of Little Pinnacle Mountain was chosen for a study of its fabric characteristics, specifically the size distribution and long dimension orientation of matrix-supported quartzo-feldspathic gneiss boulders currently visible at the deposit surface. Several approaches were taken, including random and non-random site selection, variation in the number of boulders measured per site (maximum size or 5 largest sizes), and boulder orientations relative to local slope direction or to overall down slope direction. Angular (joint-bound) to rounded boulders range in size from 4-5 m to 8-12 m; maximum dimensions are 25-30 m. We assume no change in the relative position or re-orientation of boulders within the deposit due to local stream down cutting or subsequent slumping. In situ weathering has not significantly affected the size or shape of boulders, although incipient development of sphereoidal weathering was noted locally. As a result of our study we conclude that the boulder orientation and size distribution study within one deposit appeared to show no systematic relationships among these parameters. A random distribution of boulder sizes and their orientations appears to characterize the boulder fabric along the length of the Pinnacle Mountain mass wasting deposit. The data are consistent with a debris flow origin. Conspicuous accumulations in the Rocky Bottom area are interpreted as due to rock falls rather than the emplacement of coherent debris flows.

Jones Gap State Park is a popular recreational site. Rocky Bottom is a small permanent community, with a camp for the blind. Any future mass wasting event in these areas is potentially destructive to life and property.