THERE AND BACK AGAIN: THE RECYCLING OF APPALACHIAN AND GRENVILLE SIGNATURES IN DZ U-PB RECORDS OF PHANEROZOIC NORTH AMERICA

The detrital zircon (DZ) U-Pb signature of the Paleozoic Appalachian-Ouachita-Marathon orogenic system consists of Appalachian (500-275 Ma), peri-Gondwanan (800-500 Ma), and Grenville (1250-950 Ma) age groups. For Lower Pennsylvanian deposits proximal to the Appalachian orogen, such as in the Ouachita, Black Warrior, and Illinois basins, Appalachian and Grenville age groups comprise 50-65% of the total DZ. During that time, terminal sinks, such as the Ouachita basin, and Appalachian-sourced fluvial systems likely served as insurmountable barriers to transcontinental sediment transfer. However, Carboniferous sedimentary rocks of western North America, such as in the Grand Canyon, inexplicably record Appalachian and Grenville DZ ages. Eventually, in the Late Triassic, the Chinle Formation in Utah displays the primary Appalachian and Grenville DZ signature, the result of an east-to-west fluvial routing system, along with minor age groups accrued along the way.

This Appalachian and Grenville DZ signature subsequently occurs in U-Pb records of DZ in the Mesozoic and Cenozoic of North America, sourced by either primary or recycled terranes. For example, in eastern North America, primary Appalachian-sourced DZ in the Cenomanian Tuscaloosa and Paleocene Wilcox of Alabama and Mississippi comprise 85-90% of total DZ, overwhelming other age groups. Although diluted by other age groups, recycled Appalachian and Grenville DZ signatures persist in western North America and comprise >50% of DZ from west-to-east flowing Jurassic to Holocene rivers of the Western US. The long-term persistence of Appalachian and Grenville DZ in the Phanerozoic rock record of North America, and the abundance of primary Appalachian-sourced DZ compared to the relatively diluted signature of recycled DZ transported from the west, may help determine sediment sources for modern systems of North America.