Oxygen isotope ratios in fossil wood cellulose: Isotopic composition of Eocene- to Holocene-aged cellulose
Bibliographic record
Abstract
We measured the d18O of cellulose (d18Ocel) extracted from fossil wood collected at 9 sites in the northern and southern hemispheres as a potential source of information about precipitation d18O (d18Oppt) in the past and paleotemperatures. The samples had been buried in fluvial sediments for periods of time ranging from ca. 45 million to 250 years. At the oldest localities (high latitude, Eocene- through Pliocene-age sites in Canada and Russia), mean annual temperature (MAT) esti-mates derived from the modern relationship between MAT and d18Ocel are 6–16!C lower than the MAT estimates derived from other biological proxies. Estimates of Pleistocene and Holocene mean annual temperatures are close to the modern val-ues at those sites. These results are consistent with other recent findings that the MAT/d18Oppt relationship across North America was not constant throughout the Cenozoic. Paleo-d18Oppt estimates derived from fossil cellulose and the modern North American relationship between d18Ocel and d 18Oppt are within the current annual range of d 18Oppt values at all loca-tions. The middle Eocene d18Oppt we determined from arctic cellulose samples (!21.9&) is consistent with river water d18O determined in two other studies (!19.1 & to!22&). These findings provide some evidence that a precipitation d18O signal may be retained in wood cellulose during millions of years of burial, and that latitudinal patterns in d18Oppt may
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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".