Three billion years of crustal evolution in eastern Canada: Constraints from receiver functions
Bibliographic record
Abstract
Abstract The geological record of SE Canada spans more than 2.5 Ga, making it a natural laboratory for the study of crustal formation and evolution over time. We estimate the crustal thickness, Poisson's ratio, a proxy for bulk crustal composition, and shear velocity ( V s ) structure from receiver functions at a network of seismograph stations recently deployed across the Archean Superior Craton, the Proterozoic Grenville, and the Phanerozoic Appalachian provinces. The bulk seismic crustal properties and shear velocity structure reveal a correlation with tectonic provinces of different ages: the post‐Archean crust becomes thicker, faster, more heterogeneous, and more compositionally evolved. This secular variation pattern is consistent with a growing consensus that crustal growth efficiency increased at the end of the Archean. A lack of correlation among elevation, Moho topography, and gravity anomalies within the Proterozoic belt is better explained by buoyant mantle support rather than by compositional variations driven by lower crustal metamorphic reactions. A ubiquitous ∼20 km thick high‐ V s lower crustal layer is imaged beneath the Proterozoic belt. The strong discontinuity at 20 km may represent the signature of extensional collapse of an orogenic plateau, accommodated by lateral crustal flow. Wide anorthosite massifs inferred to fractionate from a mafic mantle source are abundant in Proterozoic geology and are underlain by high‐ V s lower crust and a gradational Moho. Mafic underplating may have provided a source for these intrusions and could have been an important post‐Archean process stimulating mafic crustal growth in a vertical sense.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.004 | 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".