The low-rank Brevard-Poor Mountain-Henderson belt of northwestern South Carolina is bordered on the northwest by the Blue Ridge and on the southeast by the high-rank Inner Piedmont. This low-rank belt is a synclinorium deformed internally by isoclinal recumbent folding and tectonic sliding. An earlier isoclinal folding, progressive metamorphic event and a later faulting, cataclastic retrogressive metamorphic event can be distinguished.
The Brevard and Henderson assemblages extend along the regional strike into North Carolina and Georgia. Rocks of the Poor Mountain sequence occur in northeastern Georgia and probably extend into North Carolina. The Poor Mountain sequence consists of calcareous quartzite, marble, amphibolite, and chloritic button (muscovite augen) phyllite. The Brevard assemblage of chloritic and graphitic button phyllites and impure marble is a stratigraphic sequence that persists from Habersham County, Georgia, into North Carolina. Graphite-rich layers and the carbonate at the same horizon in the sequence indicate a sedimentary origin for this assemblage. The button lithology is not unique to the Brevard assemblage. It occurs in the Poor Mountain sequence to the southeast of the Brevard zone. To the southeast, the button lithology is commonly overlain by the Poor Mountain amphibolite. It is proposed that the Brevard and Poor Mountain assemblages are equivalent and that sedimentary facies changes account for the different lithologies observed to the southeast and along strike. Interlayering of the Henderson augen gneiss and the Poor Mountain sequence, together with the compositional variations of the Henderson, indicates a probable sedimentary origin for it, also.
A late Precambrian-Early Cambrian age is proposed for the Brevard-Poor Mountain-Henderson rocks.