Geology of the Ouachita Mountains and linkages to North American late Paleozoic orogenesis

Abstract

Correlations of Paleozoic strata from the southern Appalachian, Black Warrior, and Ouachita-Arkoma forelands show varying lithofacies and stratigraphic thicknesses for coeval deposits, as well as differences in the location of disconformities. This field trip will visit stops throughout the Ouachita Mountains and Arkoma basin to observe clastic strata variability in the Cambrian, Ordovician–Silurian, Mississippian, and Pennsylvanian periods. The spatial-temporal relationship between these units provides a first-order understanding of orogenic processes along the southeastern and southern Laurentian margin during the amalgamation of the supercontinent Pangea. We present a summary of detrital zircon geochronology from the three foreland systems and correlative stops in the Ouachita Mountains to discuss sediment provenance, paleo-reconstructions, and to identify needed geochronology information for future studies. Cambrian through Devonian units in the southern Appalachian foreland of Alabama and Ouachita thrust belt are dominated by Proterozoic Grenville (1250–900 Ma) and Granite-Rhyolite (1550–1300 Ma) province grains, with minor Archean grains. Mississippian and Pennsylvanian units in the southern Appalachian and Ouachita-Arkoma forelands exhibit similar age spectra and are primarily characterized by a dominant Grenville peak, alongside smaller Appalachian (490–270 Ma), Granite-Rhyolite, Yavapai-Mazatzal (1800–1600 Ma), and Wyoming (>2400 Ma) peaks. Proportional differences in the age spectra can be identified when comparing individual stratigraphic intervals in the forelands, and have been interpreted to represent influxes of different drainage systems associated with along strike versus perpendicular sediment routing. Mississippian strata in the Ouachita Mountains, Arkoma basin, and Black Warrior basin exhibit unique age spectra in comparison to other Ouachita and southern Appalachian signatures. A dominant Appalachian peak (<480 Ma), alongside smaller Grenville, Granite-Rhyolite, Yavapai-Mazatzal, and Wyoming peaks identified in the Batesville Sandstone of the Ouachita-Arkoma foreland, suggests a possible connection to barrier island depositional systems to the east. Pennsylvanian strata in the Black Warrior basin exhibit similar age spectra to those of samples from the southern Appalachian and Ouachita-Arkoma forelands.