26-4 Geologic map of the Wytheville 30- x 60-minute quadrangle, Virginia, North Carolina and Tennessee

Session: Geologic Maps, Geophysical Maps, 3-D Geologic Models, Digital Mapping Techniques, Map Derivatives, and Digital Map preparation (Posters)

Poster Booth No.: 38

Presenting Author:

Arthur Merschat

Authors:

Merschat, Arthur James¹, Carter, Mark W², Weinmann, Benjamin R³, Swanger, William⁴, Mangum, Holly⁵, Burton, William C⁶, Deasy, Ryan T.⁷, Parker, Mercer⁸, Webb, Fred⁹, McAleer, Ryan Joseph¹⁰, Heller, Matthew J.¹¹

(1) United States Geological Survey, Marion, VA, USA, (2) United State Geological Survey, Richmond, VA, USA, (3) United States Geological Survey, Kearneysville, WV, USA, (4) Department of Energy, Geology and Mineral Resources Program, Charlottesville, VA, USA, (5) Virginia Department of Energy, Geology and Mineral Resources Program, Charlottesville, VA, USA, (6) United State Geological Survey, Reston, VA, USA, (7) United States Geological Survey, Reston, VA, , (8) United States Geological Survey, Reston, VA, , (9) Department of Geological and Environmental Sciences, Appalachian State University, Boone, NC, USA, (10) United States Geological Survey, Reston, VA, , (11) Virginia Department of Energy, Geology and Mineral Resources Program, Charlottesville, VA, ,

Abstract:

A new geologic map of the Wytheville 30- x 60-minute quadrangle, VA–NC–TN, covers folded and faulted Paleozoic sedimentary rocks of the Valley and Ridge (VR) and polydeformed Mesoproterozoic to Paleozoic crystalline rocks of the Blue Ridge (BR).  Mapping was funded by the USGS National Cooperative Geologic Mapping Program, FEDMAP and STATEMAP Components.  The map incorporates new mapping and legacy map compilation. 

Cambrian to Mississippian sedimentary rocks of the VR are exposed in map-scale folds separated by several major thrust faults (from NW to SE): Copper Creek-Narrows, Saltville, Pulaski, Max Meadows, and Laswell faults.  Near Chatham Hill, VA, there is a restraining bend in the Saltville fault and a thrust splay to the north. Hinterland-dipping culminations at Glade and Lick Mountains expose the Neoproterozoic to Cambrian Chilhowee Group in the Pulaski-Max Meadows thrust sheet.  From W to E across the quadrangle, structures change orientation from NE-SW to ENE-WSW to E-W trending in the VR; this structural trend continues into the BR.

The Holston Mountain fault thrusts the composite BR over the VR.  In the SW, the northern end of the Mountain City window plunges NE beneath the BR thrust sheet.  West of the window, the Chilhowee Group is exposed in the SW-plunging Stony Creek syncline.  In the Iron Mountains to the NE, the group is faulted and folded into ENE-WSW plunging folds with an axial planar cleavage.  The northern French Broad massif consists of 1.3–1.0 Ga orthogneisses and paragneiss; the latter contains detrital zircon of 1.4–1.3 Ga, 1.8 Ga, and ~1.0 Ga metamorphic rims.  The Striped Rock Granite (~748 Ma) and mafic and felsic dikes intrude basement gneisses.  The Neoproterozoic Mount Rogers and Konnarock Fms. overlie basement.  The anastomosing Fries fault zone transects the southeast side of the massif.  The Gossan Lead (GL) fault juxtaposes amphibolite-facies rocks of the eastern BR over the massif.  Three packages of fault bound siliciclastic rocks are mapped in the GL thrust sheet (NW to SE):  graphitic schist and metaconglomerate of the Lynchburg Fm.; metagraywacke, schist, and mafic and ultramafic rocks of the Ashe Metamorphic Suite; and “pin-striped” mica gneiss and schist of the Alligator Back Metamorphic Suite.  ⁴⁰Ar/³⁹Ar ages document deformation at 360–340 Ma, and emplacement of the BR thrust sheet at 340 Ma. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.