Organic geochemistry of petroleum hydrocarbons in Middle to Upper Devonian outcrop samples from Mackenzie Plain area
Bibliographic record
Abstract
Rock-Eval analysis and hydrocarbon biomarker characterization have been carried out on Middle to Upper Devonian oil-stained outcrop samples collected from the Mackenzie Plain area. While an interpretation of the available organic geochemical results supports the current understanding that the Devonian Canol Formation and Bluefish Member (basal Hare Indian Formation) shales may have been the major source rocks to most oil accumulations in Middle to Upper Devonian reservoirs, an effective older source rock system is proposed to have sourced some of the oil occurrences in the area. Except for extremely organic-lean samples in which major hydrocarbon components (e.g. paraffin wax) might be mainly from contamination, organic-rich outcrop samples display hydrocarbon signatures of moderate to heavy biodegradation with their normal alkanes being partially or totally removed. Source facies parameters such as the ratios of dibenzothiophene over phenanthrene and pristane over phytane indicate their major source rocks to be shale rather than carbonate. The sterane compositions suggest most of the oil occurrences in the area are derived from either Canol Formation or Bluefish Member shale or both. Most of the oil stains also contain a high relative abundance of arylisoprenoids, a type of aromatic biomarkers known to be abundant in Devonian shales, including Canol and Bluefish units. The distribution pattern of tri-, tetra- and pentacyclic terpanes seems to be diagnostic in distinguishing the source contribution of Canol Formation from Bluefish Member. Bluefish shale is likely the main source rock for oil occurrences in the Hume Formation limestone in the Mackay Range area, in the Ramparts Formation limestone at Powell Creek, and in the Imperial Formation sandstone at Katherine Creek. In contrast, oil present in the Fort Norman Formation dolostone at Imperial Anticline and in the Imperial Formation dolostone at Prohibition Creek have a terpane composition closer to that of Norman Wells oil and Canol shale, suggesting that Canol shale is their main source rock. The apparent high oil quality (e.g., saturated fraction dominated by C13 to C18 n-alkanes) of an outcrop bitumen sample collected at the Canol-Imperial Formation contact in the Imperial River area provides strong evidence of dynamic oil expulsion, migration and accumulation within the Canol petroleum system in the area. The C29-dominant sterane distribution feature in some Ramparts Formation limestone samples from Powell Creek and Mountain River II site suggests that there might have been an active Precambrian source rock system contributing to oil accumulations in the Mackenzie Plain area.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".