PROGRESSIVE ALLEGHANIAN DEFORMATION IN METASEDIMENTS ALONG THE UNAKA MOUNTAIN FAULT, NORTHEASTERN TN: A CASE STUDY IN USING GOOGLE EARTH FOR MULTI-SCALE STRUCTURAL ANALYSIS

The Alleghanian Bald Mountain fault and Unaka Mountain fault intersect near an outcrop of Grenville basement and cover metasediments along I-26 in Unicoi County, northeastern TN. Outcrop-scale mapping and oriented thin-section analysis reveals progressive deformation of the interlayered arenaceous and argillaceous cover strata by greenschist-facies metamorphism and subsequent brittle deformation. In general, phyllitic cleavage strikes 040, dips moderately to the northwest, and lies sub-parallel to bedding. Quartz clasts are elongated and parallel to the phyllitic cleavage and show evidence of crystal-plastic deformation, weakly developed recrystallization tails, and strain fringes. An asymmetric crenulation cleavage overprints the phyllitic cleavage and dips steeply to the northwest. The sigmoidal geometry of the crenulation cleavage suggests top-to-the-northwest shear. Blocky quartz veins meters in length crosscut the cleavages and are in turn crosscut by thrust and normal faults. In general, thrust faults strike 060 and dip steeply to the northwest; fault slickenfibers trend 330 and suggest top-to-the-northwest shear. High-angle normal faults strike approximately 285 and form small grabens that crosscut earlier structures. To assist with field mapping, interpretations, and presentation, Google Earth (GE) was used to relate the micro- and outcrop-scale features to the regional structures of the Western Blue Ridge. Field data, geologic maps, and cross sections were merged with the open-source topographic data and satellite imagery available in GE. Google SketchUp was used to modify the topography and geo-reference photo mosaics on the outcrop. GE provides field geologists with a powerful tool for combining geospatial data with field data, published maps, and cross sections.