Carbon and water cycle reconstructions across the Cretaceous-Paleocene boundary through plant wax lipids
Bibliographic record
Abstract
The Cretaceous-Paleogene extinction has been one of the most heavily studied mass extinction events from the fossil record, with many aspects from the causation and effect of the extinction having been well studied, but with some areas still not having been explored in great detail. After an extended period of warming, there was a cooling event before the K-Pg extinction occurred that lasted for around 100,000 years, with the Chicxulub impact having been followed by a period of instability where plant communities were recovering. While these have been well studied, changes to the global carbon cycle remain uncertain and changes to the global water cycle have received little attention.By studying the isotopic composition of plant wax lipids preserved in sediments from across the K-Pg boundary, it becomes possible to put together a clearer image of how the carbon and water cycles were behaving up to and across the mass extinction event. These sediments were collected from southern Saskatchewan, Canada, with the lipids having been extracted from the sediments and had the abundance of individual lipid chains and isotopic compositions of hydrogen and carbon measured. Modern plant wax fractionation was used as a basis to relate the isotopic values back to the expected values of atmospheric CO2 and rain water, providing a baseline for the carbon and water cycles and observing how they change across time. Inferences on these cycles show the region was characterized by isotopically light rain water but with no long term trends in water isotope composition, while carbon values show cyclicity reminiscent of Milankovitch orbital cycles, with neither isotope record showing long term effects caused by the extinction, suggesting a relatively rapid recovery of within 10,000 years for both cycles
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".