GEOLOGICAL INFLUENCE ON THE DISTRIBUTION OF RARE PLANT SPECIES AT WADAKOE MOUNTAIN IN THE JOCASSEE GORGES REGION OF SOUTH CAROLINA

Wadakoe Mountain, in the Jocassee Gorges region of upstate South Carolina, is an area of unique plant diversity where several occurrences of rare, herbaceous plant species have been observed. At least one new species has been discovered, and several are new to South Carolina. The purpose of our study is to identify and describe the geological factors that influence the occurrence and distribution of some of these species. The geological factors being examined include bedrock type, soil composition and pH, topographic slope, and geomorphology. Geologically, this area is situated on the Chauga-Walhalla thrust complex of the Inner Piedmont. Existing geologic maps show rock assemblages that include metamorphosed sedimentary and volcanic rocks, biotite gneiss, hornblende-plagioclase gneiss, amphibolite, and mica schist. Soils in the study area, which is approximately 7 miles southeast of the Brevard Fault zone, are typically acidic and formed by weathering of the metamorphic rock. The occurrences of rare plant species in the Jocassee Gorges region may be related to areas of elevated soil pH, as suggested by some previous studies.

Specific rock types identified in the study area at Wadakoe Mountain are mica schist and amphibolite at lower elevations, a previously unmapped occurrence of carbonate-rich rock in the vicinity of some of the rare plant species, and quartzite at the top of Wadakoe Mountain. Weathering of the carbonate-rich zone and perhaps other related rock types in the study area may produce and maintain soils with elevated pH, which apparently has a significant influence on the plant species present. Based on preliminary examination of thin sections and field information, the carbonate-rich rock is interpreted as the product of hydrothermal alteration associated with faulting. The results of this investigation, combined with an understanding of structural trends of geologic features in the area including rock lithologies and faults, have the potential for leading to prediction of suitable geological conditions for additional discoveries of plant species that are rare to South Carolina and neighboring states.