Paleoenvironmental and paleoecological reconstruction of the Tyndall Stone, Selkirk Member, Red River Formation (Late Ordovician), southern Manitoba
Bibliographic record
Abstract
Tyndall Stone is used extensively throughout North America as a building and framing stone, known for its distinctive mottled pattern and high diversity and abundance of well-preserved fossils, including solitary and colonial corals, brachiopods, cephalopods, gastropods, stromatoporoids, and receptaculitids. Stratigraphically, Tyndall Stone is found in the Selkirk Member of the Red River Formation (Late Ordovician). Tyndall Stone is mined exclusively from Gillis Quarries in the town of Garson, Manitoba. The quarry is also the location of this study. At first glance the homogeneous lithology suggests a static, unchanging paleoenvironment. Upon detailed examination of a 5 m study section, however, fossil data reveal obvious environmental fluctuations that are not detectable frorn lithology alone. An overall upward shallowing sequence is suggested by an increase in stromatoporoid and receptaculitid abundance over time. An increase in sedimentation rate accompanied the upward shallowing sequence, as evidenced by the overall decrease in encrusting relationships and percentage of highly abraded horn corals. A sudden deepening event is recorded between 1.5 and 2.0 m above the base of the study section (interval 4). Within this interval, a sudden decrease in stromatoporoids and receptaculitids is observed, along with a sharp increase in encrusting relationships and percentage of highly abraded horn corals. The mottled pattern of the Tyndall Stone is attributed to the feeding activity of shrimp-like organisms burrowing their way through the firm to hard sediment in search of food. This trace fossil is recognized as the ichnogenus Thalassinoides. Cluster and correlation analyses reveal close ecological relationships between various fossil groups. Most prominent among these relationships include 1) the gastropods and cephalopods, and 2) the stromatoporoids and the encrusting coral, Protrochiscolithus. Statistical analyses also reveal similarities and dissimilarities between intervals in the study section. Most notable is the extreme dissimilarity between interval 4 and every other interval. The fossil assemblage found within the Tyndall Stone suggests a shallow marine environment, with warm to temperate water temperatures, normal salinity and an abundance of nutrients in the water column. A northerly flowing paleocurrent is inferred from the orientations of cephalopods and cardinal septa directions of horn corals. It can easily be shown that the Tyndall Stone fossils display an abundance of paleoenvironmental and paleoecological information, despite a homogeneous lithology which suggests otherwise. Interpretation of paleoenvironment, then, cannot be based solely on lithology, as fossil data can be much more sensitive to environmental change
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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 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| 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".