UPSTATE SPRINGS PROJECT, PART I: THE ROLE OF FAULT, FRACTURE, AND JOINT NETWORKS IN CHANNELING SUBSURFACE WATER FLOW IN CRYSTALLINE BEDROCK, BASED ON THE REGIONAL DISTRIBUTION OF SURFACE SPRINGS IN SLATER AND DACUSVILLE QUADRANGLES, GREENVILLE AND PICKENS COUNTIES, SOUTH CAROLINA

Numerous studies have demonstrated that breakage networks in crystalline rocks can serve as conduits for groundwater flow. A study was undertaken in Dacusville and Slater quadrangles, Greenville and Pickens Counties, SC, to determine: 1) whether the distribution of springs feeding first order streams is systematic and could be related to known regional fault, fracture, and joint orientations; and 2) whether, if present, an alignment(s) of springs might be used to define the presence of unknown breakage zones useful for further groundwater exploitation. The Inner Piedmont study area was chosen, in spite of its poor exposure, because previous 1:24,000-scale mapping indicated several faults were present, bedrock is uniform quartzo-feldspathic gneiss, a spring inventory was incomplete, and the area was accessible. A companion study has analyzed selected spring waters to identify any lateral chemical variability present.

Fieldwork in Dacusville and Slater quadrangles in Summer 2014 identified, respectively, 193 new springs/seeps and 115 new springs/seeps/bogs. We compared strikes of mapped faults, regional joints, our analysis of linear topographic elements in the study area, and the spatial distribution of our new spring locations. We assume that enhanced weathering along steep breakage zones produced the topographic linears we recognized. Two mapped fault sets and silicified microbreccia zones in Slater strike N45°-50°E and N70°-80°E; in Dacusville faults and silicified microbreccia zones strike N55°-70°E. Joint data previously collected by one of us (JG) indicates that regional joint strikes are N15°-20°E, N60°-70°E, N35°-65°W, and N80°W-N80°E. Our analysis of linear topographic elements (n=166) and spring alignments in the study area indicates both have similar dominant strikes: N40°-50°W, N50°-70°E, and E-W. Additionally, Dacusville has a N20°-29°E set of topographic linears. This NNE strike corresponds to faults outside the study area, suggesting that faults in the study area may be present but have not been recognized. Our study shows the geological structures and the springs have N60°-70°E, N40°-50°W, and E-W strikes in common. We conclude these data are all mutually corroborative, and they demonstrate structural control of spring distribution by steep breakage planes in the area.