Assessing Sediment Provenance Using Zircon U-Pb Dating in the Appalachian Basin

Thesis Abstract

The provenance of sedimentary deposits within the Appalachian Basin holds significant implications for understanding the region’s geological evolution, sedimentary dynamics, and basin tectonics. Despite extensive stratigraphic and sedimentological studies, the precise identification of source terranes remains uncertain due to complexities in sediment transport processes and post-depositional modifications. This study aims to refine sediment provenance models by employing zircon U-Pb geochronology, providing a detailed temporal framework for detrital zircon populations, which serve as critical provenance indicators. The specific objectives include (1) isolating and analyzing detrital zircon samples from selected stratigraphic units across the Appalachian Basin; (2) establishing age distributions and peak population ages using high-precision Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS); (3) integrating geochronological data with geological mapping to identify provenance sources; and (4) evaluating the correlation between zircon age signatures and known basement terranes within the region. The research adopts a predominantly empirical field-based approach supplemented by laboratory geochronology. A comprehensive sampling strategy was employed, collecting a total of 60 sandstone samples from stratigraphic levels spanning the Silurian to the Carboniferous periods, ensuring representative coverage across major basin segments. Samples were processed for zircon extraction using standard mineral separation techniques, including heavy liquid and magnetic separation, followed by mounting and polishing for LA-ICP-MS analysis. The zircon U-Pb dating was performed at the National Geochronology Laboratory, employing 10-12 spot analyses per sample to capture the variability in zircon populations. Data were statistically analyzed through kernel density estimations, concordia age plotting, and mixture modeling using IsoplotR and MATLAB to identify discrete age populations and their provenance implications. The study further applies the Pebble Morphology and Conglomerate Provenance Models to interpret sediment transport and depositional history. Expected outcomes include the identification of distinct zircon age clusters correlating with known basement terranes such as the Laurentian Shield, the Grenville, and Appalachian-Acadian orogenies, thereby clarifying sediment routing pathways. The integration of geochronological data with geological maps will facilitate the reconstruction of provenance shifts through geological time, revealing basinward evolution of sediment sources. It is anticipated that the results will demonstrate significant temporal variability in source contributions, emphasizing the dynamic tectono-sedimentary history of the Appalachian region. By providing a robust detrital zircon framework, the study aims to contribute to the refinement of regional basin models, improve sediment transport reconstructions, and enhance stratigraphic correlation efforts across the basin. This research contributes to the existing body of knowledge by combining advanced U-Pb geochronology with regional geological mapping, thus offering an improved, high-resolution provenance model for the Appalachian Basin. Moreover, it establishes a methodological template for similar provenance investigations in other tectonically complex basins worldwide. The main conclusion underscores the critical role of detrital zircon geochronology in deciphering provenance signatures amidst complex geological histories. It advocates for integrating geochronological data with structural, stratigraphic, and sedimentological analyses to develop comprehensive basin evolution models. Recommendations include expanding the sampling to include volcanic ash layers for absolute age calibration, further refining statistical approaches for population discrimination, and integrating isotopic data (e.g., hafnium isotopes) to enhance provenance resolution. The findings lay the groundwork for future research into basin tectonics, sediment routing systems, and the evolution of orogenic processes in eastern North America.