The Inner Piedmont belt probably represents the migmatitic infrastructural core of the southern crystalline Appalachians. This belt exhibits the widest area of high-grade metamorphic rocks in the southern Appalachians and is a broad zone separating structures overturned northwestward from those overturned toward the southeast. Three subparallel zones constitute the northeast-trending Inner Piedmont belt in South Carolina and northeastern Georgia. The Inner Piedmont core defines the axis and consists of an assemblage of sillimanite-grade rocks, including mica schist, biotite gneiss, granitoid gneiss, and minor amphibolite. The core is bounded by two flanks of kyanite-grade rocks of a similar character. Amphibolite and granitoid gneiss predominate within the flanks, and migmatizadon is locally intense.
Low dips predominate throughout the entire terrane, but local zones of steep foliation occur. Recumbent/reclined folds appear to characterize the structural style on all scales, and nappes associated with tectonic slides probably represent the largest-scale structures.
The Inner Piedmont is bounded on the northwest and southeast by narrow, intensely folded, highly sheared, and partially cataclastic belts of lower-grade rocks. The northwest belt is termed the Non-migmatitic-Brevard belt; the southeast belt is herein called the Kings Mountain-Wacoochee belt. These belts may be two aspects of the same tectonic feature, for they converge northeastward and southwest-ward. The Inner Piedmont belt, lying between these narrow belts, appears to converge to the northeast in Virginia and toward the southwest in Alabama.