Geologic Provinces of the United States: Appalachian Highlands Gallery

Gregory Bald.

Photo by Scott Southworth, USGS.

Gregory Bald, at 4949 feet elevation above sea level, straddles the Tennessee and North Carolina border in Great Smoky Mountains National Park. Looking north toward the Great Valley beyond the forested ridge, the grassy "bald" in the immediate foreground is underlain by meter-deep, organic-rich soil developed on graphitic slate and metasandstone of the Late Proterozoic Elkmont Sandstone that forms the base of the Great Smoky Group. In the foreground amidst the hardwood covered ridges is a lowlying grass land at about 1800 feet elevation. This is Cades Cove, a window eroded through the Great Smoky thrust sheet. The Late Proterozoic metasedimentary rocks were thrust above Ordovician Jonesboro Limestone in the Alleghanian orogeny during the Carboniferous. On the west side of the last tree covered ridge the thrust fault tips at the surface; this location is the boundary between the Blue Ridge province (south) and Great valley of the Valley and Ridge province (north). The calcite-rich carbonate rocks of the Great Valley and Cades Cove dissolve and preferentially form lowlands with fertile agricultural soils as opposed to the hardwood forested ridges that are underlain by resistant quartz-rich rock.