Linking The Tectonic, Hypsometric and Geodynamic History of The Central and Southern Canadian Shield Using (U-Th)/He Thermochronology and Global Convection Modeling
Bibliographic record
Abstract
The burial and erosion histories of continental interiors provide an important record that can test the influence of forces outside plate margin tectonism, such as dynamic topography or far-field tectonics, on continental vertical motions. The Canadian Shield, an immense region of exposed Precambrian basement far from plate margins, is well suited for this endeavor. Low-temperature thermochronology, combined with geologic constraints, can reveal past burial and erosion in areas of exposed Precambrian basement. The objectives of this dissertation are: 1) reconstruct late Neoproterozoic through Phanerozoic burial and erosion across the central and southern Canadian Shield using apatite (U-Th)/He (AHe) thermochronology and thermal history modeling, and 2) use 3D models of mantle convection to compute dynamic topography from two competing models of Paleozoic-early Mesozoic plate motions and test them against the burial and erosion record of the Canadian Shield. I first developed a model of the Phanerozoic burial and erosion history across the Hearne Province, Trans-Hudson Orogen, Superior Craton, and Grenville Province using thermal history modeling of AHe data from Precambrian basement and geologic constraints from nearby sedimentary basins and kimberlite eruptions. In the central Shield, reproducible AHe dates at ~510 <span style="color: #444444; font-family: Arial, sans-serif; font-size: 16px;">± </span>49 Ma record a substantial phase of post-650 Ma erosion. These data strongly imply that the erosion surface below the Great Unconformity, which separates Precambrian basement from overlying Phanerozoic sedimentary units, formed here after 650 Ma. In the southern shield, younger AHe dates bear on subsequent Paleozoic burial that was likely deepest in the eastern Superior Craton and Grenville Province, with lesser burial in western Superior. This sedimentary cover was likely removed in an eastward-progressing exhumation phase during late Paleozoic to early Mesozoic time. I then compared this record, along with prior work from the Slave craton, with two histories of dynamic topography drawn from 3D models of mantle convection using competing models of Paleozoic-early Mesozoic plate motions as surface boundary conditions. The plate motions imposing greater convergence between Laurentia and Gondwana during the early-mid Paleozoic and assembly of Pangea produced negative topography that fit the data better than the other model imposing more transform boundaries and passive margins.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".