A tale of two basins: juxtaposition of the Ediacaran fossil-bearing St. John’s Basin against the Ediacaran glaciovolcanic Bonavista Basin on the Bonavista Peninsula, Avalon Zone, Newfoundland
Bibliographic record
Abstract
The Musgravetown Supergroup (MSG) of the Bonavista Basin is the central unit of Neoproterozoic strata on the Bonavista Peninsula, Avalon Zone, northeastern Newfoundland. In west Bonavista, the deep-marine ca. 620–600 Ma Connecting Point Group (CPG) is unconformably overlain by the ca. 600–540 Ma terrestrial to shallow-marine volcanic-sedimentary MSG, but fault-bounded to the east by the Indian Arm Fault. On eastern Bonavista Peninsula, the Spillars Cove Fault separates the MSG from St. John’s Basin rocks, correlative with Ediacaran strata of the Avalon Peninsula (Conception, St. John’s and Signal Hill groups) as corroborated by a U–Pb age of ca. 566 Ma. Age constraints presented here confirm the regional significance of the Spillars Cove Fault that bounds temporally and stratigraphically distinct strata. Magmatic rocks of the Bull Arm Group (basal MSG) were emplaced during protracted regional extension. The onset is marked by eruption of ca. 600 Ma calc-alkaline basalt and coeval deposition of cobble conglomerate on the ca. 605–600 Ma CPG-MSG unconformity on western Bonavista Peninsula. Extension continued through extrusion of ca. 592 Ma tuffs and bimodal volcanics of the Plate Cove volcanic belt east of the Indian Arm Fault. The belt is overlain to the east by the mainly clastic Rocky Harbour Group. Its tuffs and peperite, locally dated at ca. 585 and 576 Ma, respectively, bracket the ca. 580 Ma Trinity diamictite—a shallow-marine equivalent of the deep-marine Gaskiers Formation of the St. John’s Basin on Avalon Peninsula. Small-volume alkaline basalts below and above the Trinity diamictite provide a clear spatio-temporal link between glaciation and extensional magmatism. Strata below the Trinity diamictite display features reflecting a glaciogenic origin and increase the thickness and areal extent of Ediacaran Gaskiers glacial deposits. The Gaskiers glaciation likely lasted for several million years and was coeval with ca. 600–576 Ma extensional magmatism within proto-West Avalonia or along its margin.
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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 | 0.001 | 0.001 |
| 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) | 0.004 | 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".