Abstract: New constraints on deciphering the origin of the Meguma Group in southwestern Nova Scotia
Bibliographic record
Abstract
Detailed mapping in the Digby to Liverpool area of the Meguma terrane was initiated in 1998 by the Nova Scotia Department of Natural Resources to produce a series of updated geological bedrock maps. The Meguma terrane, includes the Goldenville and Halifax formations (Meguma Group) and the younger White Rock and Torbrook formations, intruded by mainly Devonian plutonic units and overlain by Carboniferous and younger rocks. The new maps, combined with detailed petrography, geochemistry, and geochronology, have better defi ned the distribution, age, and character of the Meguma Group in southwestern Nova Scotia. The Goldenville Formation can be subdivided into a lower metasandstone-dominated Green Harbour member, a middle metasandstone/slate Government Point member, and an upper metasiltstone Bloomfi eld/Moshers Island member. The Green Harbour member, north of Yarmouth, contains a distinctive metasiltstone unit (High Head) with abundant trace fossils including the early Cambrian deep-water ichnofossil Oldhamia, suggesting that the Goldenville Formation below the fossiliferous member likely extends into the Neoproterozoic. In the area north of Liverpool, the Green Harbour member contains the Lake Rossignol unit, composed of regularly bedded metasandstone and metasiltstone with a distinct aeromagnetic pattern. The upper part of the Government Point member was shown by earlier workers to contain a Middle Cambrian trilobite faunule of Acado-Baltic affi nity. The overlying slate-rich Halifax Formation has been divided into the Cunard and Bear River members. The upper part of the Bear River Member locally contains the graptolite Rhabdinopora fl abelliformis and acritarch species that are Early Ordovician, suggesting that underlying Cunard, Bloomfi eld, and Moshers Island members are of Late Cambrian age, and that a signifi cant unconformity exists between the Halifax Formation and the overlying late Ordovician – Early Silurian White Rock Formation. Both the Goldenville and Halifax formations are locally intruded by swarms of syn-depositional mafi c sills of within-plate chemical character. A revised minimum thickness for the Meguma Group is 10 km. Protoliths of the Goldenville Formation were predominantly immature feldspathic to quartz wackes, whereas protoliths of the Halifax Formation were mainly mudstones. Preliminary whole-rock geochemical data show that most of the clastic material in the Meguma Group was deposited on an active continental margin and (or) oceanic island arc, not on an Atlantic-style passive continental margin. Although a Neoproterozoic Pan-African source is implied for the Meguma Group, the new chemical data combined with recent published work on equivalent units in northern Africa suggest that it was not deposited on the northern margin of Gondwana as previously assumed.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".