MARINE INFLUENCE IN THE UPPER ORDOVICIAN JUNIATA FORMATION (POTTERS MILLS, PENNSYLVANIA): IMPLICATIONS FOR THE HISTORY OF LIFE ON LAND
Bibliographic record
Abstract
Abstract The Juniata Formation comprises Upper Ordovician sandstone and mudstone that crops out in the Appalachian region of the eastern United States from Pennsylvania to Tennessee. An outcrop at Potters Mills, central Pennsylvania, has previously been attributed to a terrestrial environment. Because this outcrop contains numerous sub-vertical burrows and evidence for pedogenesis, it has regularly been cited as the oldest evidence for several aspects of continental ecosystem development, including the first evidence for terrestrial infauna and animal-plant interactions. We present evidence from both original fieldwork and published literature that collectively sheds considerable doubt on previous interpretations. The evidence suggests that the Juniata Formation at Potters Mills was deposited in a marginal marine setting and, as such, no evidence for early life on land can be inferred from its strata. This has significant implications for the numerous studies that have cited the Juniata Formation as providing a key record of early terrestrial evolution. Removing it from the dataset of studies that deal with the history of life on land, we conclude that currently the majority of fossil evidence from localities worldwide supports the appearance of terrestrial infauna and animal-plant interactions in the Silurian–Devonian.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".