DETRITAL ZIRCON U-PB AND TH/U COUPLED WITH ZIRCON (U-TH)/HE REVEALS NEOACADIAN UPLIFT IN THE APPALACHIAN VALLEY AND RIDGE

Sedimentation into the southernmost sector of the Appalachian foreland basin [Black Warrior basin] is interpreted to reflect (a) initial erosion of the Ouachita Mountains or (b) continental-scale sediment transport and mixing of Northern Appalachian detritus with sediment from the mid-continent. To test these models and decipher the source of Carboniferous strata in the Black Warrior basin in northern Alabama, we present U-Pb and (U-Th)/He zircon ages from the Cambrian Chilhowee Group, Ordovician Colvin Mountain Sandstone, Mississippian Hartselle Sandstone, Pennsylvanian Pottsville Formation, Silurian-Mississippian Lay Dam Formation, and Mad Indian Group. U-Pb zircon ages and zircon Th/U suggest that U-Pb spectra observed in the Carboniferous Black Warrior basin strata are temporally and chemically compatible with being locally sourced from recycling of the Cambrian and Ordovician Valley and Ridge strata, with a minor influx of Appalachian Piedmont sediment. A ~415 Ma zircon age population, however, cannot be explained by local sourcing and we propose possible origins for this sediment. Mississippian clastic strata sourced from the Appalachian Mountains requires uplift that seemingly pre-dates age estimates for major structural deformation in the Valley and Ridge province. To test this interpretation, we also present (U-Th)/He zircon HeFTY models for grains in Carboniferous and Cambrian strata that suggest orogenic uplift was underway in portions of the Appalachian Valley and Ridge by the beginning of the Mississippian and recycled early Paleozoic clastic sediment is, therefore, a compatible sediment source for Black Warrior basin clastic strata.