Petrology of the Ordovician Swan Peak Formation, Southeastern Idaho and North-Central Utah
Bibliographic record
Abstract
The Swan Peak Formation in southeastern Idaho and north-central Utah is a sedimentary unit consisting of orthoquartzite, sandstone, siltite, shale, and limestone. The formation is divisible into three members, and the lower two members each are divisible into two informal lithologic subunits. The lower member consists of a lower subunit of gray, calcareous sandy siltite composed of subangular to subrounded quartz grains cemented by quartz overgrowths, calcite, or iron oxide, and an upper subunit of black shale with minor interbedded silty quartzose sandstone and biomicrite (limestone). The middle member consists of a lower subunit of interbedded pale green shale and yellowish brown silty orthoquartzite and an upper subunit of purple orthoquartzite. The brown orthoquartzite consists of well-sorted, well-rounded very fine sand- to silt-sized quartz grains cemented by quartz overgrowths which are in optical continuity with the grains they surround. The purple orthoquartzite consists of wellsorted, well-rounded, very fine to medium sand-sized quartz grains cemented by quartz overgrowths and hematite. Hematite gives the rock its purple color. gydroxylapatite is locally abundant. The upper member is an orthoquartzite consisting of very fine to medium sand-sized, well-sorted, well-rounded quartz grains cemented by quartz overgrowths. The gastropod Murchisonia (Hormotoma) sp., the first body fossil found in the upper member, is reported. Previous work has shown that the upper member of the Swan Peak Formation and the Eureka Quartzite are similar in lithology, stratigraphy, and trace fossils. The Eureka Quartzite in the Newfoundland Range is a very fine to medium sand-sized, well-sorted, well-rounded orthoquartzite cemented predominantly by quartz overgrowths, locally by dolomite. The petrographic similarities of the two units, shown in the present study, strengthens their proposed correlation. High percentages of well rounded, polycrystalline and undulatory extinction quartz show that source areas for the Eureka Quartzite and Swan Peak Formation probably were immature sandstones or quartzites of Cambrian or Precambrian age, and./or exposed igneous or metamorphic rocks. The source for most of the sand probably was the Northwest Montana Uplift, although local sources along the Uinta Uplift undoubtedly played a minor role in supplying hydroxylapatite to the middle member and fine-grained elastics to the lower member.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".