DIGITIZATION OF GEOLOGIC MAPS: PRESERVATION AND INTERPRETATION OF DR. DOUGLAS RANKIN’S LEGACY MAPS OF THE MOUNT ROGERS AREA, VA–NC–TN

THOMPSON, Hayley N., Appalachian State University, 400 W King St Apt. H-11, Boone, NC 28607; USGS, Reston, VA 20192, MERSCHAT, Arthur J., U.S. Geological Survey, MS 926A National Center, Reston, VA 20191, WALSH, Gregory J., U. S. Geological Survey, Eastern Geology and Paleoclimate Science Center, Box 628, Montpelier, VT 05602 and SOUTHWORTH, Scott, U.S. Geological Survey, MS 926A National Center, Reston, VA 20192, thompsonhn@appstate.edu

Unpublished 1:24,000-scale geologic mapping by Dr. Douglas Rankin forms the foundation of a new detailed geologic map and geodatabase covering eight 7.5-minute quadrangles in the southern part of the Mount Rogers National Recreational Area, southwestern VA. We present (1) methods detailing digitization techniques with ArcGIS; (2) a compiled geologic map of the Mount Rogers area incorporating legacy and ongoing field studies; and (3) derivative maps including structural domain maps and surficial geologic maps.

The digitization process included several steps. (1) Scanning Mylar copies of five quadrangles within Mount Rogers into Tiff format. (2) Georeferencing and projecting in ArcMap. (3) Creation of map symbols according to hand-drawn structural symbols by Dr. Rankin, and attribution of symbol type, strike, dip, and symbol angle. (4) Geologic map geodatabases for each quadrangle house the digitized symbols and enhance navigability within the subfolders of each quadrangle. Merged geodatabases of structural data from ongoing geologic fieldwork and digitized legacy map symbols enhance structural synthesis across all eight quadrangles. (5) Final standardization of symbol size and scale preceded export of geologic map components into Adobe Illustrator for final map creation. Final digitized legacy maps and geodatabases will be submitted to the National Geological and Geophysical Data Preservation Program for long term preservation.

The compiled geology enables the following synthesis: (1) The northeastern end of the Mountain City window plunges to the NE (060°/18°) with a similar trend to folds in the overriding Shady Valley thrust sheet (066°/3°); (2) Mesoproterozoic basement rocks contain the oldest foliation (322°/88°); (3) a regional greenschist facies foliation (060°-062°/50°-60°) and lineation (140°/40°) occurs throughout most of the Blue Ridge thrust sheet; (4) amphibolite facies deformation in the Gossan Lead thrust sheet is characterized by similar orientations (066°/57°, foliation) (140°/55°, lineation); and (5) surficial geologic map of colluvial and alluvial deposits including the Piney Creek terrace deposit ~150 m above the flood plain of the New River.

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Southeastern Section - 66th Annual Meeting - 2017

DIGITIZATION OF GEOLOGIC MAPS: PRESERVATION AND INTERPRETATION OF DR. DOUGLAS RANKIN’S LEGACY MAPS OF THE MOUNT ROGERS AREA, VA–NC–TN