Oceanic anoxic event 3 in Arctic Canada—Arc volcanism and ocean fertilization drove anoxia
Bibliographic record
Abstract
Abstract The global extent of the Late Cretaceous oceanic anoxic event 3 (OAE 3) remains uncertain. It is not considered to have extended into the Boreal Realm. To test this, we examined Late Cretaceous organic- and metal-rich black mudstones of the Smoking Hills Formation in Arctic Canada. New high-precision U-Pb zircon ages indicate that deposition of the Smoking Hills Formation (88.535–78.230 Ma) was temporally coincident with OAE 3, indicating a much broader global expression of this event than previously thought. OAE 3 was likely manifest throughout the proto–Arctic Ocean (now Arctic Canada). Abundant bentonite layers and cryptotephra within the Smoking Hills Formation have rare earth element (REE) patterns that are consistent with ashfall derived from Cretaceous arc volcanism. Anomalously high organic matter content in the Smoking Hills Formation, as compared to underlying and overlying units, suggests that ocean fertilization led to enhanced productivity and metal drawdown. A peak in arc volcanism may have been a key driver of the OAE 3 event. We also explored the potential use of cadmium as a geochemical marker of volcanism and show that high volcanogenic metal loading could affect the use of Cd and other proxies for marine productivity (e.g., Zn, Cu).
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".