Abstract: The Chaswood Formation at the Atlantic Silica pit, Vinegar Hill, Poodiac, NB and its relevance to the regional depositional pattern of the Chaswood Formation
Bibliographic record
Abstract
The only known Chaswood Formation in New Brunswick is at Poodiac, south of Sussex. The Lower Cretaceous age of the deposit was recently confi rmed by Falcon-Lang et al. (Atlantic Geology, v. 39, p. 39–46). Mapping shows a gently dipping succession of braided-river gravels that overlie mudstones with lesser poorly sorted sandstones. Locally, the contact with this lower mudstone unit appears unconformable, where the mudstone dips at 60°. Flat-lying gravels, poorly preserved, unconformably overlie the dipping succession of gravels. The maximum known thickness of sand and gravel is 60 m at borehole 81-1. Only three paleocurrent indicators have been found: trough cross-bedding to 260° and barmargin planar cross bedding to 190° and 230°. Collectively, these indicate mean paleocurrents to the southwest, parallel to the fault margin of Vinegar Hill. Three new boreholes were drilled in the Chaswood Formation. VH03-3 proved a thickness of 12 m for the lower mudstone unit, which overlies Carboniferous basement. VH03-2 (27 m TD) and VH03-4 (22 m TD), to the south and west of the pit, respectively, penetrated unconsolidated sands and gravels with minor interbedded mudstone. Gravel clasts at Vinegar Hill consist overwhelmingly of vein quartz, principally grey in colour. Other rare lithologies include grey rhyolite, similar to Precambrian rhyolite of the Coldbrook Group; quartz arenite that resembles Ordovician rocks of the Miramichi terrane; staurolite-bearing metasedimentary rocks, perhaps from Mount Pleasant or the southern Miramichi terrane; purplish rhyolite; and dark hornfels similar to Silurian metasedimentary rocks intruded by Devonian granite in central New Brunswick. The heavy mineral fraction of the sands consists predominantly of ilmenite and its alteration products (40–70%) and staurolite (20–40%), with monazite, zircon and andalusite more abundant than at other Chaswood Formation localities. The overall heavy-mineral assemblage is similar to all other Chaswood Formation outliers. Monazite dates (Pe-Piper and MacKay, in prep.) show that the assemblage is principally derived from the Taconic orogen, presumably in northern New Brunswick and southern Quebec. Whether one or more rivers transported this detritus southward is unknown, although the wide geographic distribution along strike means several rivers are more probable. Regional variation in heavy mineral assemblages suggests that at any one locality, some 50% of the heavy mineral fraction is derived from local horsts and 50% from more distant sources.
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 | 0.001 |
| 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".