Conodonts identify the lower–middle Norian boundary in association with ∼224 Ma U–Pb dates from the Nicola Group, southern British Columbia, Canada
Bibliographic record
Abstract
Conodont faunas from the Castillion Member of the Selish Formation (Nicola Group) in the Merritt area of southern British Columbia, Canada, are described and determined to be early to mid-Norian in age based on biozonation established in the Pardonet Formation in NE British Columbia supported by successions in central Europe. The conodonts from two localities (Iron Mountain, Castillion Creek) show evolutionary trends through a younging sequence that serve to date and subdivide it. Hence, Ancyrogondolella vialovi is succeeded by A. ferrata n. sp. at Iron Mountain, and A . castillionensis n. sp. follows at Castillion Creek. Similarly, A. triangularis n. subsp. B is succeeded by A. diakowi , and A. uniformis is followed by A. equalis and Epigondolella tozeri . Finally, A. transformis appears as an end member and index for the Lacian–Alaunian substage boundary zone. Zircons extracted from interbedded volcaniclastics of the Castillion Member have yielded high-precision U–Pb ages of ∼224.5 Ma for the transformis Zone. This unequivocally supports the ‘long Norian’ with its base at ∼227 Ma but contrasts strongly with the astrochronologic estimate of 217.5 Ma for base Alaunian, which appears to consume most of Norian time. There is no clear explanation for this discrepancy.
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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 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| 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".