Os‐isotope insights into major environmental changes of the Arctic Ocean during the Cenozoic
Bibliographic record
Abstract
Recent studies of Lomonosov Ridge sediments provided evidence for an Eocene lacustrine stage in the Arctic Basin and concluded at its merging into global oceanic circulation some 17.5 Ma ago, with a ∼26 Ma gap in‐between. Here, Re‐Os data are used to document these events. High Os‐concentrations in the lacustrine unit and overlying transitional layer point to low sedimentary O 2 ‐conditions. Highly radiogenic Os‐isotope values mark this layer suggesting massive input of old continental material. Above, Os concentrations decrease to typical oxic‐sediment values, whereas 187 Os/ 188 Os‐ratios follow the trend observed in other oceans. However, Re‐Os isochrons from layers assigned to the upper and lower limit of the 26 Ma‐gap yield identical ages, suggesting a short transitional event marking the opening of Fram Strait and a ca. 38 Ma for the inception of marine conditions. If confirmed, this new chronology would modify views about the tectonic evolution of Lomonosov Ridge.
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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 | 0.001 | 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) | 0.000 | 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".