Geochemistry and diagenetic history of the Ordovician Lower Head Formation sandstones, western Newfoundland, Canada
Bibliographic record
Abstract
The Lower Head Formation in the Parson’s Pond area (western Newfoundland, Canada) comprises siltstones with very fine grained to fine-grained sandstones. Petrography confirms that these sandstones are matrix rich, essentially wackes, with detrital minerals including quartz, feldspar, biotite, and numerous accessory minerals. Observed petrographic features suggest that the Lower Head sediments are the distal product of erosion, with sediment sourced from the Dashwoods microcontinent and Lushs Bight oceanic tract and thoroughly mixed in an earlier basin prior to final deposition in a trench slope basin. The Lower Head Formation sandstones have low porosity, with early diagenetic cements (C1) and later calcite in crosscutting calcite veinlets (C2). Petrographic, isotopic, and fluid inclusion analyses indicate that C1 cements formed during the early stages of diagenesis. Both δ13C and δ18O isotopes for the C1 calcite cements are isotopically heavier than the C2 calcite veins. Fluid inclusion homogenization temperatures for the later crosscutting C2 calcite generally range between 78 and 116 °C, with a mean of 100.7 °C (±9.75 °C) and fluid salinities of 5.41–15.98 equiv. wt.% NaCl. Fluid inclusion gas analysis from C2 calcite confirms that CO2/CH4 generally has an inverse correlation with N2/Ar. Petroleum-bearing fluid inclusions were also recorded in C2 calcite cements, indicating that these fractures were conduits for hydrocarbon migration prior and (or) during cementation. However, the early cementation and associated low porosity of the Lower Head Formation sandstones indicate that they offer restricted pathways to migrating fluids and volatiles, and any hydrocarbon migration must have been fracture controlled.
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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 | 0.003 | 0.004 |
| Science and technology studies | 0.002 | 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) | 0.003 | 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".