Accreted terranes of northwestern British Columbia, Canada: Lithospheric velocity structure and tectonics
Bibliographic record
Abstract
Lithospheric structure beneath the accreted terranes of the northwestern Canadian Cordillera is interpreted from analyses of P wave refraction and wide‐angle reflection data. The 535 km long profile extends from the deformed and displaced ancestral North American margin across the Omineca belt suture zone and Intermontane superterrane to the Coast belt. This region is interpreted to have grown westward through a progression from thin‐skinned to thick‐skinned accretionary tectonics. Large lateral variations of velocities (2.0–6.4 km/s) within the upper 15 km correlate with the mapped geological and terrane elements; fault offsets and the imbricated base of an overlap basin are clearly identified. Inboard of the Stikine accreted terrane a zone of slow upper crustal velocities thins to the east, consistent with an interpretation of thin‐skinned accretion leaving slivers of terranes overlying a wedge of metamorphosed Proterozoic continental margin sediments. However, in the lower crust the proposed underlying cratonic ramp is not distinguished from outboard or overlying accreted crust by lateral P velocity contrasts or wide‐angle reflections. The Moho remains nearly horizontal beneath the Intermontane and Omineca belts, gradually thinning to the east from 36.5 to 35 km. To the southwest below the Coast belt and to the northeast beneath the Tintina fault, the crust thins to 32 km. Upper mantle velocities across the Coast, Intermontane, and Omineca belts are 7.8–7.9 km/s. The slow upper mantle and lower crustal velocities are indicative of high temperatures that may permit the flat Moho or weak lower crust to partially decouple the crust from the mantle. Reflections in the upper mantle between 50–70 km depth may be related to the base of the lithosphere or to heterogeneities introduced through melting or accretionary subduction events.
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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 | 0.002 | 0.004 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".