Assessing Sediment Provenance Using Detrital Zircon U-Pb Geochronology

Thesis Abstract

Understanding sediment provenance is fundamental to reconstructing sedimentary basin evolution, tectonic processes, and paleogeographic reconstructions. In light of increasing geological complexities, this study investigates the application of detrital zircon U-Pb geochronology as a precise tool for sourcing sedimentary particles within proximal and distal depositional environments. The research aims to identify the provenance of sediments from the East Valley Formation by systematically analyzing detrital zircon U-Pb ages to delineate source terranes, quantify contributions from different geological units, and interpret sediment dispersal patterns. The specific objectives include (1) characterizing the age distribution of detrital zircon populations within 150 sediment samples collected across five stratigraphic sections; (2) integrating geochronological data with mineralogical and petrographic analyses for comprehensive provenance interpretation; and (3) developing a provenance model to infer sediment transport pathways and depositional settings. The research adopts a mixed-methods approach, combining field sampling, laboratory geochronology, and statistical analyses. A stratified random sampling technique was employed, resulting in a total of 150 samples—30 from each section—to ensure representative coverage of the sedimentary units. Zircon grains were extracted through standard heavy mineral separation procedures, followed by U-Pb isotope analysis via Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The age data set—comprising approximately 6,000 individual zircon analyses—was subjected to statistical treatment, including Kernel Density Estimation, probability density functions, and multivariate statistical techniques such as Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). These methods facilitated the identification of distinct source signatures and the differentiation of sediment source terranes. Expected findings include the identification of multiple provenance signals, with dominant age peaks correlating to the Archean craton, Phanerozoic volcanic arcs, and Neoproterozoic basement rocks, indicating mixed terrane contributions. The spatial variation in zircon populations is anticipated to reveal sediment dispersal pathways controlled by paleocurrent directions and basin dynamics. The integration with mineralogical data, including heavy mineral assemblages and petrographic signatures, is expected to corroborate the geochronological interpretations, thus strengthening sediment source models. This study significantly contributes to the broader understanding of sediment dispersal mechanisms and basin evolution by advancing U-Pb zircon geochronology as a primary provenance tool in sedimentary geology. The findings will refine existing models of terrane juxtaposition and sediment routing, providing a detailed provenance framework for similar basin systems. Methodologically, the research demonstrates the efficacy of combining high-precision geochronology with statistical and petrographic analyses, offering a replicable approach for provenance studies elsewhere. The main conclusion underscores the importance of integrated analytical methodologies in sediment provenance reconstruction. It recommends the adoption of zircon U-Pb geochronology in regional stratigraphic studies and encourages further research into hydrothermal alteration effects on zircon ages. Future investigations should extend to combining detrital zircon data with other provenance proxies like isotopic signatures and detrital apatite fission-track analysis, thereby enhancing the resolution of provenance models. The results will serve as a baseline for subsequent basin evolution and resource exploration studies, ultimately contributing to reconstructive tectonics and paleoenvironmental reconstructions at regional and larger scales.