The Inner Piedmont is a large, composite, sillimanite-grade terrane that extends from near the Virginia–North Carolina border to central Alabama and consists of the eastern Tugaloo and Cat Square terranes. It is bound to the west by the Brevard fault zone and to the east by the central Piedmont suture. It is the core of the Neoacadian (360–350 Ma) orogen in the southern Appalachians and records Late Devonian–Mississippian closure and high-grade metamorphism (sillimanite I and II) of Siluro-Devonian sediments deposited in the remnant Rheic ocean basin.

The Cat Square terrane is bounded by the younger-over-older Brindle Creek fault to the...