The record of Neoproterozoic glaciation in the Windermere Supergroup, southern Canadian Cordillera
Bibliographic record
Abstract
The Neoproterozoic Windermere Supergroup (WSG) is exposed over an area of \n35,000 km2 in the southern Canadian Cordillera, and consists primarily of deep-marine \nmeta-sedimentary rocks interpreted to have been deposited during rifting and \nsubsequent post-rift thermal relaxation. The main exposures of the WSG occur within \nthrust panels and structural culminations of the eastern Cordilleran orogen. Within the \nthick stratigraphic succession (~9 km) are three units of glacigenic affinity: Toby, \nVreeland and Old Fort Point (OFP) formations. The Toby Formation is composed of up \nto 2500 m of diamictite, interbedded with conglomerate, sandstone, mudstone, \ncarbonate and mafic volcanic rocks. The Vreeland Formation ranges from 350 m to \n2000 m thick and consists of diamictite, interbedded with mudstone, sandstone and \nconglomerate. The OFP ranges from 60 to 450 m in thickness and consists of a \ndistinctive three-fold stratigraphic package of basal siltstone grading upward into \nlimestone-siltstone rhythmite, organic-rich mudstone and an overlying heterolithic unit of \ndiamictite, breccia, conglomerate, sandstone, siltstone to mudstone and limestone. A \nlocally prominent unconformity marks the base of the OFP upper member. Both the \nToby and Vreeland formations represent remobilized glacially-derived marine sediments \ndeposited by sediment-gravity flows. Deposition of the Toby Formation was faultcontrolled \nduring an active tectonic phase (rifting) whereas the Vreeland Formation \naccumulated during the subsequent quiescent phase (post-rift) with limited structural \ncontrol. The OFP is interpreted to be a regionally extensive deep-marine post-glacial \nmarker temporally associated with the glacigenic Vreeland Formation. Although direct \ngeochronological ages for WSG units in southwestern Canada are generally absent, \nhigh-precision radiometric ages of underlying and overlying igneous events constrain \nthe relative maximum and minimum timing of deposition from ca. 740-728 Ma to ca. 569 \nMa. At the base of the WSG succession, the Toby Formation may be as young as ca. \n685 Ma based on ages obtained from potential stratigraphic correlatives in the United \nStates. There is no direct age constraint for the deposition of the Vreeland Formation; \nits minimum timing is based on its stratigraphic relationship with the post-glacial OFP. \nThe middle member of the OFP was precisely dated at 607.8 ± 4.7 Ma using the Re-Os \nmethod placing it in the Ediacaran Period. Published geochemical and stable isotopic \ndata are similarly limited for all three units with only some 34Spy values available from \none section of the OFP. Recent work has focused on detailed sedimentologic and \nstratigraphic studies of the Toby and the OFP formations with future efforts being \ndirected towards integrated geochemical and isotopic research. Additional \ngeochronological constraints are needed to refine palaeogeographic models and \nstrengthen regional correlations with other North American Cordilleran glacigenic units.
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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 | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".