EVIDENCE FOR PALEOZOIC OROGENIES, TERRANE BOUNDARIES, AND MESOZOIC RIFTING FROM THE CENTRAL GEORGIA INNER PIEDMONT

New data from the central GA Inner Piedmont (IP) provides insight into Paleozoic orogenesis of the southern Appalachian crystalline core, as well as the Mesozoic rifting of Pangea. The Brindle Creek fault (BCf), which separates the Tugaloo (W IP) and Cat Square (E IP) terranes of the composite IP, is a NE striking, steeply-dipping dextral strike-slip fault in GA, while in NC, is a SW directed, low-angle thrust. The SW extension of the BCf is verified by detrital zircon geochronology and granitoid ages determined from SHRIMP analysis. Tugaloo terrane rocks (NW of the BCf) consist of the lower Tallulah Falls Fm. amphibolite-rich metagraywacke, along with the 450 Ma Lithonia gneiss, and relatively small exposures of 1.03 Ga augen gneiss. The Cat Square terrane consists of aluminous schist, amphibolite-poor metagreywackes, and at least three distinct granitoids. The High Falls granite is the most voluminous and oldest of these (424-382 Ma), while all other granitoids, in both of the IP terranes, are Alleghanian (325-299 Ma). The Towaliga fault (Tf) traces through the Cat Square terrane trending ~030, and may continue NE into SC. SW of the study area, its trend changes to ~070 as it frames the NW edge of the PMW. The Tf is an Alleghanian, garnet-grade dextral strike-slip fault that was reactivated in the Mesozoic as a sinistral strike-slip fault at significantly lower temperatures. The Oxford fault, NW of the Brindle Creek fault, also records Mesozoic movement on a ~030 trend, and both faults truncate 200 Ma diabase dikes. Abrupt truncation of a zone of voluminous plutonism by the Towaliga fault suggests significant displacement, which was likely Alleghanian; field evidence suggests Mesozoic displacement was on the order of a few km. In the Carolina superterrane, a conspicuous contact aureole surrounding the Gladesville gabbro was dated, revealing an emplacement age of 375 Ma, which supports middle Paleozoic subduction beneath the Carolina superterrane. Although evidence of Acadian/Neoacadian metamorphism is found in the IP terranes, a strong Alleghanian overprint, along with Mississippian-Permian granitoids, suggests the Alleghanian orogeny was a significant contributor to deformation, metamorphism, and plutonism in this region. Later Mesozoic rifting of Pangea was accommodated by a number of low-displacement sinistral strike-slip faults through the GA IP.