Southeastern Section–56th Annual Meeting (29–30 March 2007)

Paper No. 8
Presentation Time: 10:20 AM


BALL, Jacob B. and TRUPE, Charles H., Department of Geology and Geography, Georgia Southern University, P.O. Box 8149, Statesboro, GA 30460,

North of Asheville, NC, the western Blue Ridge thrust complex consists of a series of thrust sheets NW of the Burnsville fault that are separated by thick, greenschist-facies Alleghanian shear zones. Trupe et al. (2004) suggested that the Sams Gap-Pigeonroost (SGPR) fault, exposed near the TN-NC border, splays off the Fries fault west of the Grandfather Mountain window, and that the Fries fault therefore lies between the Burnsville fault and the SGPR fault. Near the Grandfather Mountain window, the Fries fault is a thick greenschist-facies mylonite zone. Our previous mapping suggested that the Fries fault should extend into the Sams Gap and Mars Hill quadrangles. Merschat (1977) mapped a stratigraphic discontinuity in the Mars Hill quadrangle, and suggested that it was either a fault or an unconformity. This study was undertaken to locate the Fries fault in the Bald Creek, Sams Gap, and Mars Hill quadrangles, and to determine if Merschat's discontinuity is equivalent to the Fries fault. Basement rocks between the Burnsville fault and the SGPR fault consist of intensely folded, locally migmatitic biotite-hornblende gneiss, biotite gneiss, amphibolite, and calc-silicate rock, intruded by mafic rocks of the Bakersville Intrusive Suite. These mafic rocks contain amphibolite-facies assemblages, with local occurrences of granulite-facies assemblages near the Burnsville fault. Mafic dikes below the SGPR fault are slightly lower grade. Our geologic mapping and petrographic analysis suggests that the Fries and the SGPR faults are equivalent, and that metamorphic grade in mafic dikes is consistent between the Burnsville fault and the SGPR. We did not find a greenschist-facies mylonite zone along Merschat's mapped discontinuity, and suggest that this feature may reflect deformation associated with the Burnsville fault.