Linking late Paleozoic sedimentary provenance in the Appalachian basin to the history of Alleghanian deformation

The Pennsylvanian and Permian strata in the Appalachian basin are generally interpreted to be the erosional record of the Alleghanian orogeny. Advances in our understanding of the kinematic and tectonic history of the Alleghanian orogen from study of the orogenic interior have not been integrated into interpretations of the late Paleozoic stratigraphic record. This comparative study of detrital-zircon U-Pb ages from the youngest preserved synorogenic deposits in the Alleghanian foreland (Permian Dunkard Group) to previously published ages from Early and Middle Pennsylvanian-age deposits reveals a subtle, but perhaps significant, shift in the detrital-zircon-age population. The Permian detrital-zircon ages lack 1700 to 1900 Ma and Archean-age grains characteristically present in the Pennsylvanian-age deposits, which are interpreted to indicate recycling of the lower Paleozoic passive margin. Instead, the Permian detrital-zircon-age populations are representative of the ages of rocks within the Appalachian orogenic interior. This change in the detrital-zircon-age population correlates temporally to a shift from transpressionally-inspired oblique deformation during the Pennsylvanian to foreland-vergent contraction during the Early Permian. The study demonstrates the utility of detrital-zircon dating in sedimentary basins associated with complex and protracted tectonism beyond what can be ascertained by petrographic techniques alone.