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The Paleozoic Evolution of the Southern Appalachian Orogen: A New Tectonic Model Based on Evidence from the Appalachian Foreland, Internal Crystalline Terranes, and the Exotic Carolina Superterrane

Matthew T. Huebner
University of Tennessee-Knoxville

Detailed geologic mapping, geochronologic, and geochemical analyses were conducted in the Georgia Inner Piedmont to test the hypothesis that a prominent aeromagnetic lineament represents the southwest continuation of the Brindle Creek fault, a lithotectonic terrane boundary that separates the Cat Square and Tugaloo terranes. These terranes are distinguished by detrital zircon provenance, granitoid ages, and lithologies; both terranes reached upper amphibolite facies metamorphic conditions in the Devonian through Mississippian. Evidence supports the southwest continuation of the Cat Square terrane, while differences in detrital zircon provenance reveal crucial insight regarding the paleogeographic position of the Cat Square terrane during deposition.

Devonian-Mississippian (Acadian) deformation, metamorphism, and magmatism in the Inner Piedmont are attributed to the accretion of the exotic Carolina superterrane, although several workers have presented a strong case for an earlier accretionary event, which also contrasts in kinematics and subduction polarity. To further test Acadian accretion, mafic plutons from the western flank of the Carolina superterrane (Concord Plutonic Suite), which have been suggested to be arc-derived, were sampled for geochronologic and geochemical analysis. Our findings reveal the mean age of this pulse of subduction-related plutonism shortly precedes magmatism in the eastern Inner Piedmont, which may mark the transition from B- to A-subduction and early Devonian accretion of the Carolina superterrane to the eastern Laurentian margin. This model alone, however, fails to reconcile evidence that supports an earlier accretionary event; a hybrid model that incorporates numerous compiled data from the Appalachian foreland, internal crystalline terranes, and the Carolina superterrane, is proposed.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013