Strong interplays between eustacy, nitrogen dynamics, and biodiversification between the Ediacaran and Silurian interval
Bibliographic record
Abstract
The Ediacaran to Silurian geological interval of the Podolia Basin, southwestern Ukraine, is associated with significant environmental change and biodiversification of morphologically complex biota. Using a multiproxy approach, including total Nitrogen (TN), nitrogen and carbon isotopes, total organic matter (TOC), and whole-rock geochemistry, we show that localised and transient nitrate scarcity may have persisted in otherwise oxygenated and nitrate-replete oceans during the period of extensive animal diversification. Bulk δ 15 N bulk data suggest stable partial denitrification between the middle Ediacaran and Silurian, indicating the existence of a large seawater nitrate reservoir in redox stratified waters that sustained the complex biota. Importantly, the switch to climate warming combined with the nitrate-rich waters in the early Paleozoic triggered a rapid phytoplankton and zooplankton bloom. This transition likely supported efficient nutrient flow to higher trophic levels, resulting in an increase in animal body size, biodiversification, and complexity during the Great Ordovician Biodiversification Event. Nonetheless, the upper Ediacaran and upper Silurian strata suggest a progressive near-quantitative denitrification with diazotrophic primary production as the primary nitrogen source. The generated nitrate scarcity was likely transient with no significant biological incidence since the early Paleozoic emergence and diversification of animals in the Podolia Basin are well recorded. The shift to dominant lighter marine sedimentary δ 15 N bulk composition perhaps resulted from the expansion of anoxic conditions in open marine environments during the Silurian sea-level rises and falls.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 | 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) | 0.000 | 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 teacher head, 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".