The Ammonite Catacadoceras barnstoni Beds and the Problem of the Separation of the Middle and Upper Substages of the Bathonian Stage in Northern Siberia
Bibliographic record
Abstract
Abstract— The taxonomic composition of the ammonite family Cardioceratidae is studied in the Bathonian of northern Siberia in the range of distribution of the last representatives of the genus Arcticoceras and the first representatives of the genus Catacadoceras, aiming to solve the problem of the Middle-Upper Bathonian boundary. It is shown that all previous identifications of northern Siberian material as the Middle Bathonian species Arcticoceras cranocephaloide Callomon et Birkelund, 1985, were incorrect. The misidentified specimens were mainly the Late Bathonian ammonite species Catacadoceras barnstoni (Meek, 1859) or the form with a narrow umbilicus referred to herein as Cat. aff. barnstoni. An updated ammonite zonal scale of the Middle–Upper Bathonian of Siberia is proposed, which is recommended for use both in the regional stratigraphic schemes of the Jurassic deposits of Eastern (Middle) Siberia and in the Boreal (Siberian) zonal standard of the Bathonian Stage. The extreme importance of preserving an auxiliary biostratigraphic subdivision in this scale, the Cat. barnstoni Beds, is emphasized, because of the wide distribution and abundance of the index species in Siberian sections, as well as its significance for the correlation of the lower part of the Upper Bathonian of northern Canada, northern Siberia, Franz Josef Land, and East Greenland. In addition, two intervals, i.e., the interval with Cat. aff. barnstoni and interval with Cat. perrarum, are fixed as marker levels, which are useful for rapid age determination and correlation of the Upper Bathonian deposits in Arctic sections within the upper part of the Cat. barnstoni Beds.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.001 | 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 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".