Deformation of the Macumber Formation, Antigonish Basin, Nova Scotia: implications for the Ainslie Detachment
Bibliographic record
Abstract
The Antigonish Basin is one of several Carboniferous structural basins in northeastern Nova Scotia, the evolution of which have been cited as evidence for major detachment faulting within the Vis. Windsor Group of Maritime Canada. Evidence of extension in the Antigonish Basin takes the form of a major subhorizontal structure that closely follows the basin margins and has been interpreted as part of the regional Ainslie Detachment. Placed at the top of the basal Macumber Formation and reportedly characterized by several metres of calc-mylonite, the detachment is considered to have accommodated 10—25 km of westward transport of the evaporitic Windsor and overlying Mabou groups during the late Namurian-early Westphalian. However, deformation within the Macumber Formation limestone immediately beneath the detachment surface suggests local extension of Vis. age. Recumbent intraformational folds are overlain by depositional breccias that contain previously folded fragments and are themselves recumbently folded. These relationships suggest repeated movement that began soon after limestone deposition. Furthermore, fold asymmetry and the orientation of calcite veins and small-scale normal faults suggest variable directions of extension that converge on the centre of the basin located in St. Georges Bay. While these data do not preclude the existence of the Ainslie Detachment, they suggest that the Macumber Formation in the Antigonish Basin records an earlier episode of deformation that occurred in response to local gravity sliding rather than to movement on a regional detachment surface. RESUMÉ Le bassin d Antigonish constitue l un d une série de bassins structuraux du Carbonifère dans le nord-ouest de la Nouvelle-Écosse don t l évolution a été citée comme preuve d une dislocation importante par détachement à l intérieur du groupe viséen de Windsor dans les provinces Maritimes. On relève une preuve du prolongement dans le bassin d Antigonish sous la forme d une structure subhorizontale importante qui suit de près les limites du bassin et qui a été interprétée comme une partie du détachement régional d Ainslie. On estime que le détachement, situé au sommet de la Formation basale de Macumber et caractérisé, d après ce qu on dit, par plusieurs mètres de mylonite calcique, a permis le transport vers l ouest sur dix à 25 kilomètres des groupes sus-jacent de Mabou et évaporitique de Windsor au cours de la période du Namurien tardif-Westphalien précoce. La déformation à l intérieur du calcaire de la Formation de Macumber immédiatement au-dessous de la surface du détachement, laisse toutefois supposer un prolongement local à l époque du Viséen. Les plis intraformationnels couchés sont recouverts de brèches de sedimentation renfermant des fragments antérieurement pliés qui sont eux-mêmes repliés sur un plan axial horizontal. Ces rapports permettent de supposer un mouvement répété qui a débuté peu après la sédimentation du calcaire. De plus, l asymétrie des plis et l orientation des filons de calcite et des failles normales de petite échelle laissent supposer des orientations de prolongation variables qui convergent vers le centre du bassin situé dans la baie de St. Georges. Même si ces données n écartent pas la possibilité de l existence du détachement d Ainslie, elles permettent de supposer que la Formation de Macumber dans le bassin d Antigonish évoque un épisode plus hâtif de déformation, survenu à la suite d un glissement gravitationnel local plutôt que d un déplacement à la surface d un détachement régional.
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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 | 0.001 | 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) | 0.002 | 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".