Evidence of Ejecta from the Late-Triassic Manicouagan Impact in the Blomidon Formation, Fundy Basin, Canada
Bibliographic record
Abstract
The Manicouagan impact structure in northeastern Canada is one of the largest, well-documented impact sites among Phanerozoic structures. Once considered a candidate for the cause of end-Triassic extinctions, radioisotopic dating of impact melt rock has established the age of the impact as middle to late Norian. In contrast to the clearly defined association between the Chicxulub structure and the K-Pg boundary, however, the sedimentary record of the Manicouagan impact is unusually sparse, with verified ejecta deposits currently limited to a single deep-marine occurrence (Japan) and one well-documented deposit in a continental (fluvial) setting (England). Sedimentary layers at the top of a widespread seismically deformed zone in a continental sequence in the Upper Triassic (Norian) Blomidon Formation, Fundy Basin, contain sparse, potentially impact-derived grains (shocked quartz and spherulitic grains) that are interpreted as impact ejecta that were reworked within a playa-lacustrine environment. The presence of these ejecta suggests that the seismic deformation resulted indirectly from the Manicouagan impact via reactivation of a nearby fault system. Paleomagnetic correlation of the ejecta-bearing strata in the Blomidon Formation to the Newark astrochronostratigraphic polarity time scale suggests a temporal discrepancy in the correlation of the Newark time scale to the magnetostratigraphic record of the Upper Triassic. This hypothesis is supported by recent correlations of the geomagnetic polarity time scale to the Newark time scale.
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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 | 0.002 | 0.000 |
| 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".