Integrated, high-resolution allostratigraphic, biostratigraphic and carbon-isotope correlation of Coniacian Strata (Upper Cretaceous), Western Alberta and Northern Montana
Bibliographic record
Abstract
Inoceramid bivalves are the dominant invertebrate fauna of the Coniacian and basal Santonian of the Western Canada Foreland Basin in western Alberta. In the upper lower Coniacian through to basal Santonian, six successive faunas are recognized, which provide the basis for corresponding, formally defined inoceramid zones. From bottom upward these are the zones of: Cremnoceramus crassus crassus /C. deformis deformis, Inoceramus gibbosus, Volviceramus koeneni, Volviceramus involutus, Sphenoceramus subcardissoides, and Sphenoceramus ex gr. pachti. Particular faunas represent assemblages known widely from the Euramerican biogeographic region, although they characterize mostly its northern, boreal area. The inoceramid-based biostratigraphic scheme allows correlation with other parts of the North American Western Interior and with parts of the Euramerican biogeographic region. The studied succession provides a good record of the Inoceramus gibbosus Zone, which characterizes the topmost lower Coniacian. This zone, first recognized from northern Germany, is usually absent, both in Europe and in North America, due to a stratigraphic gap resulting from a eustatic lowstand. The base of the middle Coniacian is marked by the abrupt appearance of the taxonomically variable Volviceramus fauna (V. koeneni (Müller), V. exogyroides (Meek and Hayden)), with associated Inoceramus undabundus Meek and Hayden and Volviceramus cardinalensis, newly described herein. Scaphites (Scaphites) ventricosus Meek and Hayden, the ammonite marker of the base of the middle Coniacian first appears in the late early Coniacian. The base of the upper Coniacian marks the first appearance of the characteristic northern inoceramid species Sphenoceramus subcardissoides (Schlüter), the appearance of which coincides with Scaphites (Scaphites) depressus Reeside, the ammonite marker of this boundary. Close to this boundary Volviceramus stotti also appears, which is newly described from the Canadian sections. The base of the Santonian corresponds to the abrupt appearance of Sphenoceramus ex gr. pachti (Arkhangelsky). The studied sections demonstrate that the appearance of new inoceramid faunas (lowest occurrence of Cremnoceramus crassus crassus (Petrascheck), of various species of Volviceramus, Sphenoceramus subcardissoides (Schlüter) and of S. ex gr. pachti) takes place immediately above major marine flooding surfaces, suggesting a close correspondence between evolutionary and/or migration events and episodes of relative sea-level rise.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".