Extracting Metamorphic Histories Utilizing U-Pb Laser Ablation Zircon Geochronology from the Southern Appalachians Crystalline Rocks and Detrital Sediment

The southern Appalachian mountain belt is an accretionary orogen that formed in the southeastern United States through several phases of oceanic subduction and continental collision during the Paleozoic Era and culminated in the formation of the supercontinent Pangaea. Although many U-Pb zircon ages have been collected from the igneous, metaigneous and metasedimentary rocks in the crystalline core of the southern Appalachians, there remain opportunities to better reconstruct the metamorphic and magmatic history of the southern Appalachians through the lens of zircon geochronology. Such data are valuable in identifying genetic relationships between candidate terranes of the orogen. Herein, I present laser-ablation U-Pb zircon data from metamorphic rocks of the Blue Ridge and Inner Piedmont provinces, which I subdivide into different petrogenetic populations based on their age-depth, and U/Th characteristics. I use these relationships to identify metamorphic rims, metamorphic crystals, and magmatic crystals. Further, I compare these results with a similar analysis of detrital zircons from Cretaceous-Recent sediments and sedimentary rocks from the coastal plain and continental shelf of South Carolina, which provide a more spatially integrated record of metamorphic history. Metamorphic U-Pb zircon ages were extracted from the three aforementioned datasets, revealing three major ages modes of ca. 340 Ma, 360 Ma, and 420 Ma. Other researchers have produced metamorphic ages from the Ordovician Taconic orogeny (ca. 470 – 440 Ma), but this Taconic signature is lacking from the U-Pb zircon metamorphic ages produced in this study. Whereas crystallization ages from exposed plutons and metaplutonic rocks from the Blue Ridge and Piedmont are spatially dominated by 320 – 300 Ma and 450 Ma magmatic ages, the detrital record from the Appalachian foreland basin and modern inner continental shelf reveals a more protracted history with dominant pulses from ca. 480-390 Ma and ca. 350-300 Ma. Integrating these spatially diverse metamorphic ages with the detrital magmatic record can help constrain the timing of terrane accretion, metamorphism, and magmatism within the southern Appalachian orogenic system.