THE PARADOX BASIN AND SEDIMENT ROUTING IN NORTH AMERICA DURING THE LATE PALEOZOIC

Late Paleozoic collision along the North American eastern and southern margins, the Alleghany and Ouachita-Marathon orogenies respectively, sourced sediment to a cross-continental drainage network. Appalachian-derived, Grenville (1.0-1.3 Ga) age detrital zircons first appear in passive margin strata of the Grand Canyon in the late Mississippian and remained a strong presence throughout the rest of the Paleozoic. Contemporaneous intracontinental deformation, the Ancestral Rocky Mountains, compartmentalized much of the western interior and affected western reaches of the Mid-continent by creating tectonically isolated basins. For example, fluvial and alluvial fan strata of the Pennsylvanian–Permian Paradox Basin, which is more proximal than the Grand Canyon to the Appalachian source of Grenville-aged zircons, contain no zircons with ages of 1.0–1.3 Ga implying a strong degree of tectonic isolation. However, these facies and associated detrital zircons elucidate complex drainage networks internal to the Paradox Basin. Along-strike variability in Uncompahgre Uplift bedrock ages facilitate discrimination of transverse and axial drainage systems within the Paradox Basin. Transverse alluvial fans and rivers delivered sediment westward from the adjacent Uncompahgre Uplift as an axial system, less than 30 km from the uplift’s thrust front, routed sediment to the north. In contrast, Paradox Basin eolian deposits exhibit zircon age spectra similar to those documented in the Grand Canyon indicating a well-mixed, extra-basinal sediment source and a transport pathway largely separate from the fluvial facies. Paradox Basin detrital zircon data highlight the degree of tectonic isolation and local sediment sourcing precipitated by Ancestral Rocky Mountain exhumation as well as the ability of eolian transport to introduce externally sourced sediment into isolated basins.