The Ocmulgee fault is a fundamental boundary within the Piedmont of central Georgia separating North American, Piedmont terrane rocks from exotic rocks of the Avalon (Carolina) terrane. Contrasts in stratigraphy, metamorphic grade, and aeromagnetic signature coincide with the fault trace. The fault comprises a broad zone (ca. 2 km) of foliation dipping steeply southeast and containing localized syn- and post-thermal-peak right-lateral strike-slip shear zones. Oblique dextral convergence between the Avalon and Piedmont terranes, most likely around 350 Ma, produced the steep zone and its attendant dextral shear zones. Steep foliation within the fault zone resulted in its predisposition to later faulting.