DETAILED GEOLOGIC MAP OF THE INNER PIEDMONT AND CAROLINA SUPERTERRANE AT THE NORTHEAST END OF THE PINE MOUNTAIN WINDOW, CENTRAL GEORGIA

A new 1:50,000-scale detailed geologic map of the NE end of the Pine Mountain window (PMW), GA, has been compiled and includes parts of the Inner Piedmont (IP) Tugaloo (Tu) and Cat Square (CS) terranes, and the NW flank of the Carolina superterrane (Cst). The PMW contains Grenville basement overlain by early Paleozoic(?) metasandstone, quartzite, and schist. The Tu terrane contains lower Tallulah Falls Fm. amphibolite, metagraywacke, and schist intruded by the ~443 Ma Lithonia Gneiss, and truncated by the Jackson Lake (JL) fault. The JL fault separates Tu and CS terranes through central Georgia and is equivalent to the Brindle Creek fault recognized in western North Carolina, although the two differ somewhat in structural style. CS terrane rocks consist of metagraywacke and schist intruded by ~380 Ma High Falls Granite, which comprises most of the Lloyd Shoals plutonic complex (LSPC). The High Falls Granite contains 1-10 cm microcline megacrysts and foliation concordant with peak sillimanite-grade regional foliation (S₂), and is the youngest granitoid crosscut by the JL fault, providing a maximum age of the fault. Alleghanian granitoids in the LSPC include the Indian Springs and Dows Pulpit Granodiorites, which truncate S₂, confirming a regionally penetrative pre-Alleghanian fabric. The Indian Springs Granodiorite also occurs in the Tu terrane and crosscuts the JL fault, indicating pre-Alleghanian juxtaposition of the Tu and CS terranes and a minimum age for the fault. The Towaliga fault, which separates the IP from the PMW, truncates Alleghanian granitoids and both the JL and Box Ankle faults. The Box Ankle fault is an upper amphibolite-facies, northwest-directed thrust that frames the E end of the PMW and juxtaposed CS terrane rocks above the PMW. The fault is folded axial planar to S₂, indicating pre-Alleghanian movement. The Cst is sutured to IP rocks along the Neoacadian-Alleghanian Ocmulgee fault and Rumble shear zone. Numerous small-scale lower greenschist-facies mylonites are present, and are spatially related to brittle silicified cataclasite faults that share mutually crosscutting relationships with ~200 Ma diabase dikes. These shear zones may represent late-stage Alleghanian deformation or deformation associated with the early stages of Pangea breakup.