Provenance of the Cretaceous Athabasca Oil Sands, Canada: Implications for Continental-Scale Sediment Transport
Bibliographic record
Abstract
ABSTRACT: The McMurray Formation of the Athabasca Oil Sands is one of the largest hydrocarbon resources on Earth and contains an extensive record of Early Cretaceous sedimentation. The provenance of the sandstones that constitute this formation has remained largely unknown. New U-Pb detrital zircon ages (n = 848) record a complicated and variable provenance history that involves several major tectonic regions from across North America. The McMurray Formation contains detrital-zircon signatures indicating sediment sources associated with the Canadian Shield, eastern North America, and the Canadian Cordillera. Vertical stratigraphic changes in the dominant detrital-zircon signatures in the McMurray Formation indicate that provenance of the sediment varied during deposition of the unit. Lowermost deposits in the formation are characterized by zircons with ages of ca. 1800–1900 Ma and ca. 2600–2800 Ma, interpreted as derived from the Canadian Shield. Most of the sediment in the McMurray Formation contains detrital zircons with U-Pb ages of ca. 300–600 Ma and ca. 1000–1200 Ma, interpreted to have been derived originally from Appalachian and Grenville sources in eastern North America. Uppermost samples in the McMurray Formation contain abundant zircons with ages less than 250 Ma, derived from the North American Cordillera. When and how sediments from eastern North America were transported to the Athabasca Oil Sands region of Canada is unclear. We propose the sediments were transported either directly from eastern North America during the Early Cretaceous or recycled during the Early Cretaceous from sub-Cretaceous sedimentary strata in western Canada or the southwestern United States. The presence of Proterozoic and Paleozoic zircons in the Athabasca Oil Sands highlights the importance of Appalachian-derived sediment in the Lower Cretaceous stratigraphic record of western Canada.
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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 | 0.003 | 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) | 0.003 | 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".