Crust of eastern North America preserves a record of the supercontinent cycle
Bibliographic record
Abstract
The northeastern North American lithosphere, integral to supercontinent cycles and the Wilson Cycle concept, remains largely inaccessible at depth. Employing innovative P-wave receiver function methods, we unveil the upper ∼60 km of the lithosphere, focusing on the Appalachian Front (AF). Three distinct lithospheric blocks emerge, revealing a central 150 km wide region of thick (45+ km) crust with a gradational Moho and elevated P-to-S velocity ratio (κ), flanked by thinner (35–40 km) crust regions with lower κ and a sharp Moho. Abrupt changes align with Proterozoic (St. Fulgence Shear Zone (SFSZ)) and Paleozoic (Baie Verte–Brompton Line (BVBL)) tectonic boundaries, but not with the AF and the Red Indian Line (RIL), two of the first-order structural boundaries in the region. An elevated κ area coincides with the ∼450 Ma Charlevoix impact crater. Lithosphere NW of the BVBL retains Neoproterozoic supercontinent assembly structures, while the lithospheric affinity of the SE region remains unclear. Despite the RIL marking the Pangaean suture, connecting Paleozoic Laurentian and Gondwanan rocks, no changes are observed at depth. This suggests a thin-skinned tectonic regime and/or significant lateral transport. We propose either Gondwanan lithosphere extension to the BVBL or a subsurface Laurentia–Gondwana suture SE of its surface trace.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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 source (direct Gemma or distilled Codex), 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".