Ordovician-Silurian Boundary Interval in the Williston Basin Outcrop Belt of Manitoba: A Record of Global and Regional Environmental and Biotic Change
Bibliographic record
Abstract
FIELD TRIP OBJECTIVES During latest Ordovician to earliest Silurian time, deposition and biotas were influenced globally by environmental changes that led to glaciation and subsequent deglaciation in southpolar Gondwana. At the centre of equatorial Laurentia, the Williston Basin provides a record of global and regional change in an epicontinental sea. Classic localities in southern Manitoba will be compared with sites north of Grand Rapids and northeast of The Pas, including the only known exposures of the Ordovician – Silurian boundary in this vast basin. New research, integrating lithostratigraphy, biostratigraphy, and C-isotope stratigraphy, suggests that deposits of latest Ordovician (Hirnantian) age are present and that the Ordovician – Silurian boundary is at a higher position than previously thought. Strata exposed in southern and west-central Manitoba provide a superb opportunity to examine this extraordinary time in Earth’s history. This field trip will focus on the Stony Mountain, Stonewall (Figs. 1, 2), and Fisher Branch formations. These predominantly carbonate strata record environments and events leading up to and following the major Hirnantian glacial episode. The succession of fossils represents the culmination of the ‘Great Ordovician Biodiversification Event’, the Late Ordovician mass extinction, and the Early Silurian recovery. The Williston Basin outcrop belt in Manitoba provides a dip section, from relatively basinal deposits in the south to more marginal in the north. On Day 1, we will visit the type sections of the three formations in the southern part of the outcrop belt. Exposures of correlative strata in two areas within the northern part of the outcrop belt will be examined on Days 2 and 3. This field trip complements several GAC–MAC 2013 Special Sessions, including Williston Basin and Other Intracratonic Basins – Sedimentology, Stratigraphy, Paleontology and Resources; Advances in Phanerozoic Geoscience in the Hudson Bay Basin, Foxe Basin and Hudson Strait; and Evolving Carbonate Environments from Precambrian to Modern: Sedimentological and Geochemical Perspectives; and the symposium on Life and Times of Phanerozoic Seas (in Honour of Rolf Ludvigsen).
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".