DETRITAL ZIRCON PETROCHRONOLOGY REVEALS EARLY ALLEGHANIAN ARRIVAL OF PIEDMONT-SOURCED SEDIMENT IN THE SOUTHERN APPALACHIAN FORELAND

The Ordovician-Permian Appalachian orogen developed from a sequence of nearly synchronous events along the eastern North American (Laurentia) margin. Determining sedimentary provenance using detrital geochronology is limited given the ubiquity of some age populations and coeval syntectonic features. To investigate a new approach for data display and interpretation, we present U-Pb zircon ages from Appalachian foreland basin strata and metasedimentary rocks from the Appalachian Piedmont, with a focus on using Th/U values in zircon to distinguish zircon grains that originated in compressional arcs, extensional magmas, and metamorphic systems. Results show zircon U-Pb isotopic ages and Th/U from Paleozoic strata in the southernmost Appalachian Mountains do not display age or compositional similarities to zircon from the Ouachita segment of the orogen. Zircon from Mississippian-Pennsylvanian strata (Hartselle Sandstone and Pottsville Formation) correlate in age and composition to similar age and composition zircon within the Eastern Blue Ridge of Alabama and Inner Piedmont of North Carolina. Furthermore, Lower Cambrian sedimentary sources may be fingerprinted with respects to the presence/absence of post-Grenville (<950 Ma), orogenic collapse-signature zircon grains and Archean-Paleoproterozoic zircon U-Pb populations. The approach we present here attempt to circumvent limitations in U-Pb detrital geochronology when multiple sediment sources contain similar-age zircon populations from different tectonic settings to interpret provenance that is applicable to future and legacy datasets.