Reconstructing environmental and microbial ecosystem changes across the Permian-Triassic mass extinction at Lusitaniadalen, Svalbard
Bibliographic record
Abstract
The Permian–Triassic environmental crisis triggered fundamental changes in marine ecosystems, culminating in the most severe biodiversity crisis of the Phanerozoic. Yet, the environmental and geochemical conditions governing the crisis and ecosystem recovery remain debated. The sedimentary succession at Lusitaniadalen, Svalbard, deposited in the Permo–Triassic Boreal Realm, offers insights into mid-latitudinal, shallow marine ecosystem responses. In a multiproxy study combining lipid biomarker and geochemical data, we reconstruct environmental conditions and microbial ecosystem dynamics across the Permian–Triassic environmental crisis. Generally low enrichments of the redox-sensitive trace elements Re, V, U and Mo, predominantly negative Ce anomalies, and a pristane/phytane ratio > 1 suggest mainly oxic conditions in the investigated interval. However, while transient dysoxic to anoxic episodes recorded across the extinction horizon support that deoxygenation contributed to the severity of the mass extinction, the earlier occurrence of similar episodes of deoxygenation in the late Permian challenges the hypothesis of global anoxia as the sole extinction driver at this site. Lipid biomarkers reveal a post-extinction increase in abundance of long-chain n-alkanes derived from terrestrial plants due to increased terrigenous discharge into shallow marine settings across this interval. Pristane and phytane, lipid biomarkers mainly derived from chlorophyll, reveal a pronounced regional increase in primary productivity following the environmental crisis. The composition of the lipid biomarker inventory recorded in early Griesbachian strata remains distinct from the pre-crisis composition, and did not recover towards the pre-crisis state within the studied interval.
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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 | 0.001 | 0.001 |
| 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".