Facies Analysis and Architectural Elements Within a Fluvio-Estuarine Sedimentary System: The Lower Cretaceous Bituminous Sandstones of the MacMurray Formation, Alberta (Canada)
Bibliographic record
Abstract
Abstract In north-eastern Alberta (Canada), the fluvio-estuarine McMurray Formation constitutes the main bitumen accumulation of the Athabasca Heavy Oil Province. Deposited within the fluvial-to-marine transition zone, the McMurray clastic succession is characterized by the lateral and vertical juxtaposition of a wide variety of depositional processes. This led to complex lithofacies variations responsible for uncertainties in predicting reservoir heterogeneities. In this context, a realistic paleogeographic reconstitution is necessary to localize sandy reservoirs and optimize the exploitation of bituminous sandstones. The sedimentological study of the McMurray reservoir, based on outcrops and subsurface data (cores, well logs, seismic profiles), has been undertaken along a 150 km north (distal) -south (proximal) transect. Facies analysis permits to constrain depositional environments within the McMurray Formation. We document in detail facies associations corresponding to continental (fluvial/palustral/paleosols facies), estuarine (interaction between tide and fluvial processes) and marine environments (wave-tide to wave dominated processes). A particular attention has been paid to the nature, size, geometry and bounding surfaces of architectural elements (i.e. fluvial or estuarine channels, IHS/point-bars, tidal bars, incised valley, emerged surfaces). Stratigraphic correlations, combined with cartographic analysis, allow to evaluate how these sedimentary bodies are related in time and space. The McMurray Formation has been previously sub-divided into three units: the fluvial dominated lower McMurray, the fluvio-estuarine middle McMurray and the marine dominated upper McMurray. We notably demonstrate, on the base of size and amplitude of IHS, that the middle McMurray may be sub-divided into stratigraphic sub-units. We also point out the significance of oxidized surfaces overlain by abrupt grain size changes. Such surfaces are important clue for sequential analysis and may have a regional extent. They should be taken into account as a potential accurate correlative tool for the McMurray Formation.
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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 | 0.004 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".