Tectonic Origin of the Mississippi River Using Evidence from Detrital Zircons from the Cretaceous McNairy Sand
Date of Award
M.S. in Engineering Science
Jennifer N. Gifford
Brian F. Platt
Inoka H. Widanagamage
University of Mississippi
U-Pb geochronology of detrital-zircon in the McNairy Sand from southern Illinois, Kentucky, Tennessee, and northern Mississippi characterizes when the Ancestral Mississippi River changed its flow direction from westward in the Early Cretaceous, progressing south in the Late Cretaceous. The aim of this study is to investigate the sediment deposition patterns of the McNairy Sand unit the northeastern margins of the Mississippi Embayment to reconcile the known records of westward and southward drainage of the Mississippi River through time. The sediment accumulated during the reactivation of the Late Proterozoic to Early Paleozoic Reelfoot rift system at the end of the Mesozoic Era. U-Pb ages and Th/U ratios of zircon grains from this study are used to characterize the drainage pattern of the Ancestral Mississippi River during the Maastrichtian (~70 Ma). The McNairy Sand records evidence of sedimentation driven by the tectonic activity of the Reelfoot rift system, which resulted in the topographic low for the drainage system of the Mississippi River. Detrital zircons, yielded dominantly, ~1350 - 900 Ma U-Pb ages (Grenville; 80%), and smaller population of U-Pb ages ~1500 - 1350 Ma (Mid Continent Granite-Rhyolite; ~8%); ~490 - 450 Ma (Taconic - Acadian; ~6%), ~900 - 500 Ma (Gondwanan Terranes; ~4%), 1800 - 1600 Ma (Yavapai Mazatzal; ~2.4%), and >2500 Ma (Wyoming-Superior provinces; ~0.002%) suggesting an Appalachian region provenance. The results support characterizing the provenance and age of deposition, clarifying the drainage patterns of that period and orientation of the Ancestral Mississippi River and its tributaries. The U-Pb age signatures couple with the Th/U ratio zircon grain suggest two sourced regions that routed sediments in the Mississippi Embayment, 1. Appalachian Foreland Basin and 2. the Appalachian Piedmont region.
Eli, Manuel Dela, "Tectonic Origin of the Mississippi River Using Evidence from Detrital Zircons from the Cretaceous McNairy Sand" (2022). Electronic Theses and Dissertations. 2430.
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