A lithogeochemical assessment of the Lower Cretaceous sediments of the Scotian Basin
Bibliographic record
Abstract
Whole rock geochemical analyses have been made from conventional core samples of Lower Cretaceous sandstones and shales from the wells: Naskapi N-30, Alma K-85, Alma F-67, Glenelg N-49, Glenelg E-58, North Triumph B-52, Peskowesk A-99 and Dauntless D-35; and from picked cuttings samples from the wells: Sambro I-29, Dauntless D-35, Fox I-22, Crow F-52, and Argo F-38. Samples with abnormal abundances of P, Mg, Ca and Fe result from important amounts of carbonate or phosphate cernent; after removing these samples, 79 reliable analyses were obtained. Published geochemical discrimination diagrams for clastic sediments were evaluated. These diagrams aim to identify effects of source-area weathering, hydraulic sorting during transport, and the character of the source area rocks ( and hence by inference, their tectonic setting). The chemical effects of source area weathering are difficult to interpret because they may be mirrored by the effects ofburial diagenesis. However, there is petrographic evidence for rapid erosion and transport from the source area. Source area rocks were identified as predominantly of intermediate to felsic composition, characteristic of a continental island arc or passive margin. This is consistent with the petrographically identified source areas predominantly within the Appalachian orogen. Sorne discrimination diagrams suggest that the sources to the western Scotian basin were more mafic and those to the east more felsic, consistent with petrographic evidence for important K-feldspar supply to the east and predominant plagioclase supply to the west. Chemical discrimination diagrams did not provide unambiguous characterization of the predominant source rocks for different parts of the basin. Nevertheless, there are significant changes in elemental abundances in different parts of the basin that are interpreted to represent supply from different source rocks. In the east, Peskowesk (and generally also Fox and Dauntless) sandstones are lower in Ti and have a high K/Rb ratio. Sandstones from the Glenelg and North Triumph fields have distinctively high Hf and Th/U ratios and low La/Sm ratios compared with wells both to the east and west. Mudrocks show an increase from west to east in Nb and Y and a decrease in Sr and Hf. There are systematic variations in Th content ofmudrocks between the western (Naskapi and Alma), central (Glenelg and North Triumph) and eastern (Fox, Peskowesk and Dauntless) areas. Data are insufficient in most wells except Alma and Peskowesk to document stratigraphie variation in key elements. Systematic variation in the chemical composition of sediment in the Scotian Basin is consistent with published petrographic evidence for supply from several different rivers. Regional variation in some elements such as Ti and K may have important consequences for diagenesis. More samples will be needed to evaluate hypotheses proposed in this report.
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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".