Improved Os-isotope stratigraphy of the Arctic Ocean
Bibliographic record
Abstract
[1] The history of the Arctic Ocean remained poorly known until the 2004 IODP coring of Lomonosov Ridge sediments. Early studies of the recovered sequence demonstrated the existence of an Eocene ‘lake-stage’ prior to the transition to marine conditions. The marine stage onset was inferred to be ∼17.5 million years -Ma- ago, thus implying a nearly 26 Ma gap between the lacustrine and marine episodes, and an unusual tectonic history for Lomonosov Ridge, in order to explain this gap. More recently, Rhenium-Osmium (Re-Os) isotope measurements of the transition from the lacustrine to marine sediments suggested a much earlier inception of marine conditions and the absence of any significant gap between both episodes. Here, an improved Osmium isotope stratigraphy and Re-Os data concur to assign a Late Eocene age (∼36 Ma) to the marine invasion, consistent with a relative change in sea level on top of Lomonosov ridge, either from tectonic origin or from another cause.
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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) | 0.001 | 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".