Paleoenvironmental and paleoecological reconstruction of the Chemahawin Member (Cedar Lake Formation; Silurian) at Lundar, Manitoba
Bibliographic record
Abstract
A mid-Early Silurian stromatoporoid-dominated biostrome within the upper, Chemahawin Member of the Cedar Lake Formation (Interlake Group; Silurian) is exposed within a quarry near Lundar, Manitoba. This highly dolomitized structure, previously classified as a bioherm, displays little evidence of topographic relief, but the density of skeletons within the unit, and the complex interactions among fauna, justify classification as a biostrome. Statistical tests were employed to assess the distributions of stromatoporoids and corals between localities in the quarry, and between stratigraphic intervals within localities, in order to recognize spatial and temporal trends within the biostrome. The faunal assemblage of the Chemahawin Member was analyzed in terms of abundance, species diversity and dominance, skeletal growth forms, and skeleton size. Within the Chemahawin biostrome, different microenvironments at various positions within the structure are interpreted from spatial variation in the distribution of fauna. Vertical trends in faunal distribution suggest short-term ecological succession as the biostrome transitioned from a pioneer community to a climax stage. In the southwest corner of the quarry, closely spaced facies represent a gradual progradation of the biostrome over previously unsuitable muddy substrates. It is interpreted from directional measurements of elongate fossils that a prevailing paleocurrent originated from the northeast, and the southwest corner likely represents a protected, back-reef setting. Examination of a subsurface drill core from Lundar Quarry North revealed facies arrangements similar to those within the quarry. A second core from nearby Mulvihill West Quarry revealed correlative facies, although the interval equivalent to the biostromal facies was not as well developed, indicating the limited lateral extent of the structure. The Chemahawin Member represents a transgressive-regressive cycle, with reefal development at the time of maximum transgression, corresponding to the interval of geological time when reefs were most widespread globally in the Silurian. Although large mid-Silurian reefs are common structures within other basins on the North American continent, reef development within the Williston Basin was limited and patchy, suggesting that conditions were less favourable for large-scale reef growth.
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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 | 0.002 | 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".