Taphonomic variations in Eocene fish-bearing varves at Horsefly, British Columbia, reveal 10 000 years of environmental change
Bibliographic record
Abstract
The Eocene Horsefly locality in British Columbia has yielded many fossil fishes, insects, and plants. Its varved sediments make it ideal for study of temporal changes in environment and fish morphology. Several intervals of diatomaceous varves indicate a deep, stratified lake setting. Earlier studies focused on morphological and taphonomic change during the 700-year H2 interval and morphological change during the 10 000-year H3 interval. The present study uses taphonomy as an index for environmental change during the ten millennia represented by H3, comparing taphonomic changes with the morphologic changes found earlier. The H3 interval records deposition in deep water, indicated by dominance of the fish genera Amyzon and Eohiodon. Quiet water conditions are indicated by minimal fin disarticulation. Hypoxia at the time of fish death is confirmed by open mouths of most fish specimens, while cool water on the lake floor prevented full flotation of fish carcasses. Water depth, temperature, and oxygenation fluctuated during H3 deposition. Periods of cooler, deeper, more hypoxic water are indicated by greater numbers and size of Amyzon specimens and by less disarticulation of skull and abdominal bones. Periods of warmer, shallower, more oxygenated waters are indicated by more disarticulation, less fin tetany, smaller fish specimens, and greater diversity of species. Correlations between the taphonomic changes and morphological changes in A. aggregatum are weak. Therefore, the morphological changes are not easily explained as ecophenotypic or short-term evolutionary responses to changes in physical lake conditions.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".