A Framework for Integrating Isotopic Signatures in Sedimentary Basin Thermochronology

Thesis Abstract

Sedimentary basins record evolving thermal histories and geomorphological processes, yet isotopic signals used to constrain thermochronological interpretations are often treated in isolation from stratigraphic and basin-scale processes, leading to non-unique or biased inferences of cooling ages and maturation timelines. This study develops a cohesive framework for integrating isotopic signatures within sedimentary basin thermochronology to improve resolution of thermal histories and timing of exhumation and burial events. The specific objectives are (1) to synthesize isotopic systems (e.g., U-Pb in accessory minerals, Lu-Hf, Sm-Nd, 40Ar/39Ar, and stable isotopes in carbonates and clays) within a unified thermochronological framework; (2) to quantify the sensitivity of individual isotopic systems to burial, diagenetic, and metamorphic overprinting across stratigraphic sequences; (3) to formulate a probabilistic model that couples isotopic systematics with basin-scale thermal models and stratigraphic architectures; (4) to test the framework against multiple well-documented basins with independent geochronological controls; and (5) to provide practical guidelines for data acquisition and interpretation that reduce non-uniqueness in thermal histories. The methodology adopts a mixed-methods design combining quantitative thermochronological modeling with qualitative synthesis of basin stratigraphy. The population comprises sedimentary basins with well-characterized stratigraphy and available isotopic datasets from mineral phases common to thermochronology (zircon, apatite, titanite, carbonate clumped isotopes, and clay minerals). A stratified random sampling approach will select 12 basins across tectonic settings, ensuring diversity in burial histories and temperature regimes. Data collection will entail reanalyzing existing isotope datasets (n ? 250 samples) and generating new measurements where gaps exist. Analytical techniques include U-Pb zircon dating on detrital grains and tomographic apatite fission-track measurements, Lu-Hf isotope analyses in accessory minerals, 40Ar/39Ar step-heating for thermochronometry, carbonate clumped isotope thermometry for palaeotemperature reconstruction, and stable isotope ratios (?18O, ?13C) in carbonates and clays to constrain diagenetic overprinting. Instrumental methods will be accompanied by thorough sample authentication, petrographic characterization, and cathodoluminescence imaging to ascertain mineral phases. The data analysis pipeline integrates a Bayesian hierarchical framework that links mineral-specific closure temperatures to basin-scale thermal models derived from burial and exhumation histories, with forward-modeling of isotopic system behavior under varying thermal regimes. Model validation will be performed using cross-validation against basins with independent thermochronological constraints (e.g., magnetostratigraphy, stratigraphic unconformities). Sensitivity analyses will examine the influence of burial rate, heat flow, presence of fluid pathways, and diagenetic overprinting on isotopic ages and temperatures. The study will also incorporate a decision-support tool enabling practitioners to assess isotopic data compatibility with proposed thermal histories. Expected findings include (i) a quantified, system-specific diagnostic framework detailing how each isotopic signal responds to burial, reheating, and diagenetic events within sedimentary sequences; (ii) a probabilistic ensemble of thermal histories consistent with integrated isotopic constraints, reducing non-uniqueness in exhumation timing by 25–40% in test basins; (iii) identification of robust isotope combinations (e.g., zircon U-Pb with apatite fission-track and carbonate clumped isotopes) that synergistically constrain maximum and minimum temperatures and times; and (iv) practical recommendations for sampling strategies and analytical workflows that optimize isotopic information content given budgetary constraints. Contribution to knowledge lies in the development of a holistic, integrative framework that formally fuses isotopic signatures with basin thermochronology, enabling more reliable reconstructions of thermal histories, burial/exhumation timings, and diagenetic histories in sedimentary basins. The framework advances theory by operationalizing the interaction between isotopic systematics and basin-scale thermal processes within a Bayesian, data-driven context, while offering transferable methodologies for basins worldwide. The main conclusion anticipates that integrated isotopic constraints, when embedded within a probabilistic basin thermochronology model, yield more precise and accurate thermal histories than isolated isotopic or thermochronological analyses. Recommendations include adopting the proposed framework as a standard practice in basin studies, expanding isotope datasets for underrepresented basins, and developing open-source software to facilitate broader adoption of the Bayesian integrative approach.