Building Laurentia: evidence from P and S-wave teleseismic tomography and SKS splitting in precambrian northern Canada
Bibliographic record
Abstract
The geology of northern Hudson Bay, Canada, spans >3 Ga Earth's history including several Paleoproterozoic orogenies, most notably the Trans-Hudson Orogen (THO). The THO is potentially analogous to the ongoing Himalayan orogen, but whether modern-day-style plate tectonics was responsible is debated. Northern Canada is also an ideal location to study the development of mantle keels: Laurentia's keel underlies both Archean and Proterozoic zones, bringing existing Archean keel-formation hypotheses into question. I explore these issues via teleseismic body-wave tomography and SKS shear-wave splitting analysis of mantle seismic structure. During relative arrival-time analysis, when the network aperture is large (~4000 km), some raypaths retain source-side structure due to subducting oceanic crust and mantle lithosphere waveguides. Mitigation of this source-side influence is essential to avoid travel-time dataset contamination. Final tomographic models reveal complicated internal structure to the Archean Churchill plate and the THO. North-central Hudson Bay is seismically distinct from the THO, consistent with the view that one or more micro-continents were caught between the principle colliders, complicating simple two-plate THO models. Network-wide shear-wave splitting delay times of δt >1 s require a mantle contribution. However, North America has moved too slowly since 50 Ma to create an asthenospheric 'basal drag' anisotropic fabric. Evidence for multi-layered fossil lithospheric anisotropy beneath Archean zones supports episodic development hypotheses for keel formation. Southern Baffin Island is underlain by dipping anisotropic fabrics. When reviewed in light of co-located slow wavespeeds extending north from the Hudson Strait in tomographic models, these data support the view that Paleoproterozoic material underthrust Baffin Island in a modern-style subduction zone setting during the THO.
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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) | 0.001 | 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".