OXYGEN AND CARBON ISOTOPE GEOCHEMISTRY OF LATE ORDOVICIAN BRACHIOPODS FROM ANTICOSTI ISLAND, QUEBEC
Bibliographic record
Abstract
The δ13C and δ180 values and elemental compositions of 29 Late Ordovician (Hirnantian Stage) shells from eight different brachiopod species from the Ellis Bay Formation, Anticosti Island, Quebec, were measured to evaluate their fidelity of chemical and isotopic preservation. Three groups of Mendacella shells from three separate Hirnantian time periods were also analyzed to provide δ C and δ O curves for this time interval. Significant differences in δ C and δ 0 values among species, shells of the same species, and within individual shells from early to late growth stages suggest that original isotopic compositions were retained. Differences in chemical compositions between shell-matrix and shell-cement boundaries also suggest minimal alteration. These brachiopods are therefore deemed suitable proxies for the δ C and δ 0 values of Hirnantian seawater. The carbon and oxygen isotope compositions of Mendacella are consistent with previous studies. A large, positive excursion at the end-Hirnantian is suggestive of a cooling event.
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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 | 0.001 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".