THE DADEVILLE COMPLEX, ASSOCIATED FAULT KINEMATICS, AND IMPLICATIONS FOR TECTONIC EVOLUTION OF THE SOUTHERN APPALACHIAN INNER PIEDMONT

The southern Appalachian’s Inner Piedmont (IP) Dadeville Complex (DC) of Alabama (AL) and Georgia (GA) originated as sedimentary and volcanic rocks intruded by batholith-scale igneous bodies that were poly-deformed during high-grade metamorphic events and transported via thrusting during collisional tectonism. The DC forms a large klippe that was structurally emplaced above rocks of the eastern Blue Ridge, Brevard Fault Zone (BFZ), and Opelika Group (OG), nested in the core of the Tallassee/Newnan-Tucker synform (TS). The DC consists of an array of metaigneous, metaplutonic, and metasedimentary rocks including the Ropes Creek Amphibolite, Agricola Schist, Chattasofka Creek Gneiss and equivalents (~461 Ma), Camp Hill Gneiss (~ 446-448 Ma), and various mafic-ultramafic suites. The DC is fault bounded to the NW by the Katy Creek fault (KCF) and to the S and SE by the Stonewall Line fault (SLF). Multiple F₂ folds affect the SLF causing it to exhibit its deformed appearance in map view. An examination of the fault separating the DC from the JGG further supports the kinematic evidence that the SLF is folded around the hinge of the TS and is truncated by the KCF near Jacksons Gap (JG), AL. Both the Abanda fault (AF) and KCF appear to exhibit negligible offset south of JG and an increase in net displacement to the northeast, where the KCF replaces the SLF as the structural base of the DC. This supports the interpretation that the fault at the structural base of the DC that curves around the hinge of the TS is the deformed SLF. The KCF and AF form prominent, continuous (>90 kilometers), topographic lineaments that suggest a different kinematic history when compared to the SLF. If the KCF and SLF thrusts are to be considered the same fault, then comparable kinematic characteristics would be present on either flank of the DC allochthon. Instead, the differences observed in both AL and GA suggest the KCF and SLF both formed late in the Alleghanian kinematic sequence, with the SLF predating the KCF based on kinematic and geometric differences.