An Early/Middle Devonian 40Ar/39Ar Age for the Charlevoix Impact Structure (Quebec, Canada) - An Approach Closer to Reality
Bibliographic record
Abstract
Introduction: The ~54 km Charlevoix impact structure is hosted in ~0.9 Ga crystalline rocks of the Grenville Province of the Canadian Shield that are overlain by Middle Ordovician sedimentary rocks. Impactites mainly comprise impact melt rocks of variable appearance and textures, as well as pseudotachylitic breccia dikes in the shocked crater basement. Although the Charlevoix impact structure has been studied for a long time, no precise data for the age of the impact event exist. The maximum impact age is defined by the occurrence of shatter-coned Middle Ordovician limestones (~460-450 Ma) in downfaulted parts of the impact structure [1]. The southeastern part of the impact structure is overthrusted by the northern Appalachian front along the Logan’s Line. The Late Devonian terminal Acadian orogeny (~377 Ma [2]), thus, marks the minimum impact age [1]. Existing Age Constraints: The first K-Ar ages for impact melt rocks obtained by [3] yielded (recalculated) Carboniferous ages between 321 and 356 Ma for the Charlevoix impact structure. 40 Ar/ 39 Ar laser spot total fusion analyses of impact melt
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.014 | 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".