Ichnological insights into deoxygenation across the Cenomanian–Turonian Boundary Oceanic Anoxic Event 2 in the northern extent of Western Interior Seaway (west‐central Alberta)
Bibliographic record
Abstract
ABSTRACT In‐depth ichnological and sedimentological analyses of the Cenomanian–Turonian boundary Oceanic Anoxic Event (OAE2) from the Western Interior Seaway of west‐central Alberta reveal a persistent physico‐chemically stressed setting. The interval is characterised by a dominantly diminutive and diminished ichnological assemblage, with familiar ichnotaxa (e.g. Phycosiphon , Chondrites , Nereites , Planolites , Teichichnus , Cylindrichnus and Palaeophycus ), fugichnia and navichnia ethological groups, and evidence of meiofaunal reworking and two other indistinct biodeformational fabrics. Grouping trace fossils into four ichnoguilds (the fugichnia ichnoguild, the Planolites ichnoguild, the Phycosiphon ichnoguild and the Chondrites ichnoguild) reveals fluctuating oxygen, salinity and sedimentation stress over time. Integrated analysis of ichnological characteristics, ichnofacies and ichnoguilds reveals five different bottom water oxygen scenarios, including: (i) poorly oxygenated, (ii) severely dysoxic, (iii) extremely dysoxic, (iv) episodic storm‐injected oxygen and (v) anoxia. Comparing trace fossil data with carbon isotope data, where the OAE2 is defined as a positive excursion, reveals oxygen trends over the event. Oxygenation was found to be highest below the OAE2 and declined rapidly over the Cenomanian–Turonian boundary. The Cenomanian–Turonian boundary itself is characterised by low and constantly fluctuating depositional dissolved oxygen, but never persistent anoxia. Counterintuitively, the most deoxygenated interval occurs after the termination of the OAE2 event. The delayed onset of lowest oxygen levels may be due to peak transgression occurring post‐OAE2 and slowed northward migration of warm oxygen‐poor Tethyan waters.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| 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) | 0.000 | 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".