Phanerozoic sedimentary cover history of the Hudson Platform: a heuristic modeling perspective

Kalin T. McDannell , Paul B. O'Sullivan, Kerry Gallagher, Scott Boroughs

Understanding the long-term erosion and burial history of cratons is challenging due to the incompleteness of the rock record. Here we present a study involving laser ablation apatite fission-track dating of three Canadian Shield basement samples collected adjacent to the Ordovician nonconformity on the Hudson Platform. Compared to a conventional analysis, our samples are characterized by up to 3× the number of dated grains and > 6× the number of track-length measurements. The large dataset enhances Bayesian QTQt thermal history inversions and helps define conditions for AFTINV modeling within a heuristic Frequentist framework. Modeling is guided by a 'hierarchical testing' philosophy regarding model selection, which allows us to (i) assess the Bayesian model’s ability to infer plausible time-temperature paths from the data (i.e., assess sensitivity), (ii) compare the model results with the known geology, and (iii) recursively parameterize models with respect to the previous results. QTQt inversions without time-temperature constraints favor two reheating events, suggesting cooler, near-surface conditions during the late Neoproterozoic–early Paleozoic and Jurassic–early Cretaceous, consistent with major Hudson Platform unconformities. Models indicate that the exposed basement near the Hudson Bay Basin reached peak burial around 317 ± 18 Ma, likely occurring between the Famennian and Carnian stages. A second burial event occurred in the late Mesozoic to mid-Tertiary between the Aptian and Chattian stages, with peak burial estimated at ca. 46 ± 15 Ma. The easternmost sample, near the Moose River sub-basin, may have reached peak burial conditions at 83 ± 7 Ma (within uncertainty of other models), coinciding with Cretaceous sea level rise. Thermal histories align with preserved basin geology indicating burial during the Ordovician–Devonian and late Cretaceous. However, peak burial may have occurred in the Pennsylvanian and Eocene, implying a more extensive sedimentary cover than is currently preserved in the Hudson Bay Basin. These thermal histories are broadly consistent with burial reconstructions from the Williston Basin and Slave craton to the west. The now-exposed shield was formerly covered by sedimentary rocks estimated to be ∼1.24 ± 0.21 km thick during the Paleozoic and ∼1.37 ± 0.26 km thick on average from the latest Mesozoic through the middle Cenozoic.