Assessing the Effect of Large Igneous Provinces on Global Oceanic Redox Conditions Using Non‐traditional Metal Isotopes (Molybdenum, Uranium, Thallium)
Bibliographic record
Abstract
Large igneous provinces (LIPs) have occurred episodically throughout Earth's history, with the most severe events causing profound disturbances to Earth's climate and biosphere that likely influenced the course of metazoan evolution. One environmental perturbation caused by LIP emplacement is a change in global oceanic redox conditions. The uranium (U) and molybdenum (Mo) isotope systems are relatively established tracers of global oceanic redox conditions, particularly for the extent of anoxic and euxinic seafloor, whereas the thallium (Tl) isotope system is emerging as a tracer for the extent of well-oxygenated seafloor characterized by manganese (Mn) oxide burial. In this review, we discuss how these metal isotope systems can be used to infer changes to global oceanic redox conditions through the cascade of environmental perturbations caused by LIP emplacement, focusing on the three events (Cenomanian-Turonian, Toarcian, and Permian-Triassic) that have received the most attention. Existing isotope mass-balance models for these metals indicate an expansion of oceanic anoxia and euxinia (by ~1 to 2 orders of magnitude greater than the modern ocean) accompanied LIP emplacement during these events. Future studies, ideally utilizing a multi-isotope approach on the same samples and coupled with improvements in oceanic metal isotope mass balances and modeling, are expected to provide more precise and accurate estimates of the spatiotemporal extent of oceanic anoxia/euxinia expansion and how this relates to the magnitude, location, and style of LIP events.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| 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 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".