Upper Mississippian sediment provenance during initial Black Warrior foreland basin development

ABSTRACT Mississippian and Pennsylvanian strata in the Black Warrior foreland basin record deformation and deposition during a period important for understanding the orogenic intersection between the southern Appalachian and Ouachita thrust belts. Previous sediment provenance interpretations for the Upper Mississippian Hartselle Sandstone employed either a continental-scale drainage from the north that incorporated northern Appalachian and Midcontinent material, or a regional-scale drainage from the south that incorporated southern Appalachian, Ouachita, and peri-Gondwana sources. We present detrital zircon U-Pb geochronology and (U-Th)/He thermochronology from the Upper Mississippian Pride Mountain Formation and Hartselle Sandstone in the northern Black Warrior foreland to determine sediment provenance and advance paleogeographic reconstructions. The Pride Mountain Formation and Hartselle Sandstone produce detrital zircon U-Pb age spectra characterized by a dominant Appalachian (500–350 Ma) population alongside smaller Grenville (1250–900 Ma), Granite-Rhyolite (1550–1300 Ma), Yavapai-Mazatzal (1800–1600 Ma), Trans-Hudson (2000–1800 Ma), and Wyoming Province (>2500 Ma) populations. Cross-correlation coefficient analysis shows that Black Warrior foreland samples contain age spectra dissimilar from coeval deposits in the Appalachian, Michigan, Forest City, and Illinois basins. These results preclude a northern-derived sediment-routing system for Pride Mountain and Hartselle Sandstone strata. All populations from the Pride Mountain–Hartselle Sandstone age spectra are present in pre-Mississippian, Paleozoic bedrock from the Ouachita–southern Appalachian thrust belts, and potentially in buried peri-Gondwana rocks. Monte Carlo inverse mixing models, developed to test the viability of a southern-derived sediment provenance, support an interpretation wherein Upper Mississippian strata in the Black Warrior foreland were sourced predominantly from the developing southern Appalachian thrust belt, with additional contributions from the easternmost Sabine terrane (Maya block) and Ouachita thrust belt. Sixteen detrital zircon grains were doubled-dated for (U-Th)/He thermochronology to evaluate the cooling signature of Silurian grains in the Pride Mountain Formation and Hartselle Sandstone. Ten of 16 grains produced Devonian through Pennsylvanian helium dates, and a cluster of six U-Pb Silurian grains produced Silurian–Devonian helium dates. Inverse temperature-time modeling of these six dates produced a rapid late Silurian–Early Devonian cooling signature, suggesting a volcanic arc source in the detrital spectra. Our results require a sediment-routing network that incorporated material in what is now the hinterland portion (eastern Blue Ridge and Inner Piedmont) of the southern Appalachian thrust belt, followed by transport of material along structural strike toward the southwest (present-day coordinates), a northern rerouting of sediment at the Ouachita–southern Appalachian orogenic bend, and ultimately deposition northward into the initial Black Warrior foreland. We envision an analog to this interpretation to be the modern Yarlung-Tsangpo-Brahmaputra-Ganges drainage network, which sources material from the Himalayan-Tibet orogenic system, transports it through the eastern Himalayan syntaxis southward into Bangladesh, and ultimately deposits it into the Bay of Bengal. This model integrates well with regional lithology and facies thickness trends, sandstone thin-section petrology, and basin subsidence evolution.