Archaean oxygen oases driven by pulses of enhanced phosphorus recycling in the ocean
Bibliographic record
Abstract
Earth's first rise in atmospheric oxygen between about 2.43 billion and 2.1 billion years ago fundamentally transformed the atmosphere and oceans, setting the foundation for the evolution of complex life. However, geochemical evidence reveals intermittent oceanic oxygen oases before the rise of atmospheric oxygen, although the mechanisms that drove the production and accumulation of oxygen remain poorly constrained. Here we present redox-sensitive trace metal and iron speciation data, and phosphorus phase partitioning results, for a 2.93-billion-year-old drill core from the Red Lake area, Canada, to reconstruct oceanic phosphorus cycling and links to oxygen production in the dominantly anoxic, iron-rich Archaean ocean. Our data document one of the earliest known intervals of surface water oxygen accumulation, predating the first accumulation of atmospheric oxygen by about 500 Ma. These intervals were preceded by ferruginous intervals and intervals of enhanced sulfide availability, which led to pulsed increases in oceanic phosphorus bioavailability via anoxic recycling from sediments. Enhanced phosphorus bioavailability would have helped stimulate photosynthetic primary productivity and organic carbon burial, probably exerting a major control on the episodic development of oxygen oases in the late Archaean ocean. This, in turn, led to a critical transitional phase in the development of an oxygenated surface environment.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".