Complex iron and sulphate reducing Cretaceous sedimentary system revealed by extreme isotope values
Bibliographic record
Abstract
Abstract The iron and sulphur isotope compositions of sedimentary pyrites have been extensively used as a proxy for microbial metabolisms and redox evolution of the oceans. We illustrate the benefit of in‐situ and coupled study of Fe and S isotopes on sedimentary pyrites from late mid‐Cretaceous sediments from the Central Apennines, Italy. We report extremely low δ56Fe values for sedimentary pyrites (as low as −4.7‰) and unusual high δ34S values (as high as +88.9‰). We propose a model that explains these extreme values but also the large range of pyrite δ34S and δ56Fe values as well as the considerable microscale variations in this values. These isotopic compositions were likely produced by microbial dissimilatory iron reduction in the shelf sediment, transportation of Fe2+ via an iron shuttle, production of heavy SO4 by pyrite precipitation in the water column, diffusion and advection of SO4 and H2S, and finally bacterial sulphate reduction.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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".