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

The detrital zircon (DZ) U-Pb signature of the Appalachian-Ouachita orogenic system is dominated by Grenville (ca. 1250–950 Ma) and Appalachian (ca. 500–275 Ma) age groups and dominates the Phanerozoic record of North America. This study compares Pennsylvanian to modern DZ U-Pb data from across North America and demonstrates a persistent Appalachian signature, including a recycled Appalachian signature across western North America. Lower Pennsylvanian deposits proximal to the Appalachian orogen are 50–75 % Appalachian- and Grenville-age DZ, representing the key component in the primary Appalachian signature. It remains unclear how the Appalachian signal was propagated to the West, but Appalachian-age DZ in Carboniferous western Laurentian strata may have been derived from the northern Appalachians in the United States and Canada or the Ellesmerian orogen.

Triassic DZ samples document transcontinental fluvial systems with headwaters in the Ouachita-Marathon orogen that reached the western Laurentian margin. Subsequent Jurassic-Cretaceous samples, however, indicate drainage reversal due to the rise of the Mesozoic Western Cordillera. A persistent Appalachian signature exists in these western-sourced, eastward-flowing systems—a phenomenon that continues to the present. Samples are frequently composed of >40% Appalachian- and Grenville-age DZ. However, none of these systems are interpreted to be sourced by primary Appalachian or Grenville terranes, suggesting a recycled Appalachian signature. The persistent Appalachian signature, originally sourced by the linking of two orogenic terranes, continues to be the dominant contributor in the DZ record of North America.