High-resolution record of global cooling during a large Mississippian positive carbon isotope excursion
Bibliographic record
Abstract
The Kinderhookian-Osagean Boundary Excursion (KOBE) is among the largest positive carbon isotope excursions in the Phanerozoic Eon, but the temporal relationship between the KOBE and global cooling is not well understood. Previous attempts to establish connections between perturbations to the carbon cycle and global climate were hampered by the need to assume seawater δ 18 O values, a reliance on fossils with incomplete stratigraphic distribution, and disagreement between records from conodonts and brachiopods. Here, we present a high-resolution clumped isotope record from a Lower Mississippian section from north-central Iowa. When considered in the context of facies changes and evidence of diagenesis, these data show that a positive shift in δ 13 C—possible evidence of increased organic carbon burial—precedes cooling of 5–7 °C, and provides a maximum constraint on global ice volume of slightly less than modern quantities in the prelude to the main phase of the Late Paleozoic Ice Age. This evidence supports hypotheses that the KOBE was the result of a change in organic carbon burial dynamics (upland plant expansion, deep basin burial, expanded suboxia) rather than those that posit that initial cooling led to enhanced carbon burial. We demonstrate that clumped isotope analyses of bulk carbonate rocks from shallowly buried, open-marine environments that experienced early cementation provide complementary constraints to existing paleoclimate proxies.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".