Sequence stratigraphic model for repeated “butter shale” Lagerstätten in the Ordovician (Katian) of the Cincinnati, Ohio region, USA
Bibliographic record
Abstract
The “butter shale” Lagerstätten of the Cincinnati Arch have produced an abundance of articulated trilobites, along with assorted bivalves and cephalopods. These bluish gray shales are rich in clay, poorly calcified, and show vague internal bedding in outcrop. Butter shales form a repetitive motif with similar lithological and paleontological characteristics, suggesting conditions existed that can be explained by the interference between different orders of sequence stratigraphic cyclicity. The characteristics that define butter shales include rarity of coarser interbeds, homogenous, fine grain size, and abundance of burial horizons. The overriding control is siliciclastic sediment supply. During third-order transgressions, sediment supply to the basin is too low to produce thick shale-prone intervals. Conversely, during third-order falling stages, sediment supply is generally too high to favor butter shale deposition. Butter shales formed preferentially during a third-order highstand systems tract, and two subtly different variants resulted from the superimposed effects of higher order cycles. Highstands moderated by small-scale transgressions are characterized by lower background sedimentation and fewer, thinner mud deposition events. Superposition of small-scale sea-level fall on highstands produced increased background sedimentation, higher silt, and patchy fossil occurrences. Juxtaposition of various scaled highstand systems tracts provided the optimal butter shale conditions, characterized by elevated mud influx and frequent episodic burial events, leading to abundant, articulated trilobites and associated fauna. In these scenarios, episodic events provide sufficient mud to smother local faunas and create a soft, fine-grained substrate that prohibited recolonization by taxa adapted to firm substrates. Each scenario differs from the others with respect to sedimentology and faunal composition.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.018 | 0.002 |
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".