COMPILED DATA FOR THE HENDERSON AND WESTERN ROANOKE RAPIDS 1:100K SHEETS: UTILIZING GIS TO UNRAVEL STRUCTURAL GEOLOGY PROBLEMS

The North Carolina Geological Survey has been conducting geologic mapping in the Henderson and Roanoke Rapids 100K sheets in the eastern Piedmont of NC using partial support from the USGS STATEMAP-EDMAP programs. Prior to this effort, lithologic and structural data were in 26 standalone 1:24K based GIS geodatabases. The data have been compiled into a single GIS geodatabase of more than 30,000 attributes. This dataset includes over 10,000 planar and 1,700 linear fabric elements, and 4,500 fracture measurements. Used in conjunction with detailed geology polygons, the dataset has the potential to unify macroscale structures, refine lithologic contacts and provide a robust structural analysis at a regional scale that can easily be shared with collaborators.

The eastern Piedmont contains a series of late Paleozoic third-order terranes juxtaposed by the dextral Eastern Piedmont fault system (EPFS) as a result of Alleghanian deformation. These terranes contain multiple suites of plutonic, volcanic, volcaniclastic, and sedimentary lithodemes that have variable tectonothermal overprints. These lithodemes contain either shallow crustal, suprastructural rocks recording greenschist facies metamorphism, or mid-crustal infrastructural rocks recording amphibolite facies and penetrative structural transposition. Numerous Pennsylanian-Permian granitoid plutons intrude these eastern Piedmont terranes and their crustal boundaries. The Late Triassic Deep River rift basin and associated brittle faults overprint these terranes and mark the eastern to central Piedmont transition.

Traditional foliation and lineation maps are difficult to interpret. As such, we are experimenting with color-coded symbology to generate geologic form surface maps illustrating structural patterns across the eastern Piedmont. Preliminary analyses of these maps demonstrate: (1) a prominent penetrative foliation generally oriented NE-SW marking EPFS strain that can be traced in both infrastructural and suprastructural terranes; (2) a mineral lineation prevalent in infrastructural terranes that trends in the same orientation as planar surfaces in the EPFS but reorient away from its linear shear strands; and (3) granitoid intrusions have locally reoriented planar surfaces.