Actualistic approaches to interpreting the role of biological decomposition in microbial preservation
Bibliographic record
Abstract
Taphonomic processes, especially post-mortem biological decomposition, act as crucial controls on the microbial fossil record. Information loss during the fossilization process obscures interpretation of ancient microbial ecology and limits our view of preserved ecosystems. Conversely, taphonomic information can itself provide insight into fossilization pathways and processes. This information-gain approach requires specific attention to taphonomic patterns in ancient assemblages and robust modern analogue data to serve as points of reference. In this study, we combine experimental taphonomy with decomposition models in order to constrain taphonomic hypotheses regarding Proterozoic microfossil assemblages. Several filamentous and coccoidal prokaryotic and eukaryotic phototrophs were evaluated for taphonomic pattern over the course of a short (~100 days) decomposition experiment. In parallel, simple numerical models were constructed to explain potential taphonomic pathways. These analogue data were then compared to two Mesoproterozoic fossil assemblages, the ~1.5 Ga Kotuikan Formation, Siberia, and the ~1 Ga Angmaat Formation, Canada. Concordant with previous experiments and observations, our results suggest that sheath morphology is more persistent than cell/trichome morphology during early stages of decomposition. These experiments also suggest that taphonomic change in cell morphology may follow one of several trajectories, resulting in distinct taphonomic endpoints. Model output suggests two categories of underlying mechanism and resultant taphonomic trajectory: (1) uniform decomposition, resulting in a low overall taphonomic grade and poor preservation, and (2) faster decomposition of structurally compromised individuals, producing a final population with better overall preservation of very few individuals. In this experiment, cells of coccoidal organisms exhibit the first pattern and trichomes of filamentous organisms and some sheaths exhibit the second. Comparison with preserved microfossil assemblages suggests that differences in taphonomic pattern between parts of an assemblage could be useful in assessing taphonomic processes or degree of taphonomic loss in an entire assemblage.
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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 | 0.004 | 0.013 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".