Stratigraphy and sedimentology of early Pennsylvanian red beds at Lower Cove, Nova Scotia, Canada: the Little River Formation with redefinition of the Joggins Formation
Bibliographic record
Abstract
The coastal cliffs along the eastern shore of Chignecto Bay, Nova Scotia contain one of the finest Carboniferous sections in the world. In 1843, Sir William Logan measured the entire section as the first project of the Geological Survey of Canada, and defined eight stratigraphic divisions. We have re-measured a section corresponding almost exactly with Logan’s Division 5 in bed-by-bed detail. The strata are exposed in the wave-cut platform and low-relief bluffs of a 2 km-long section at Lower Cove, near Joggins, north and south of Little River. This 635.8 metre-thick succession until now has been included within the basal part of the Joggins Formation, and overlies the Boss Point Formation. However, the studied strata are lithologically distinct, and are formally recognized as the new Little River Formation. This formation is bounded by regionally important surfaces and is traceable inland for 30 kilometres from its Lower Cove type section. Facies analysis indicates that it represents the deposits of a well-drained alluvial plain dissected by shallow rivers characterized by flashy flow. It can be clearly distinguished from the underlying Boss Point Formation (Logan’s Division 6) by its much smaller channels, and from the overlying Joggins Formation (Logan’s Division 4) by lack of coal seams and bivalve-bearing limestone beds. Palynological assemblages indicate that the Little River Formation is of probable late Namurian to basal Westphalian (basal Langsettian) age, and is a likely time-equivalent of the informal Grand-Anse formation of southeast New Brunswick. Resumé Les falaises côtières longeant le rivage oriental de la baie Chignectou, en Nouvelle-Écosse, abritent l’un des stratotypes carbonifères les plus intéressants dans le monde. Sir William Logan avait mesuré en 1843 l’ensemble du stratotype dans le cadre du premier projet de la Commission géologique du Canada et il avait défini huit divisions stratigraphiques. Nous avons mesuré à nouveau un stratotype correspondant presque exactement dans ses détails couche par couche à la division 5 de Logan. Les strates affleurent dans une plate-forme d’érosion et des falaises de relief émoussé d’un secteur de deux kilomètres de longueur à l’anse Lower, près de Joggins, au nord et au sud de la rivière Little. Cette succession de 635,8 mètres d’épaisseur avait jusqu’à maintenant été incluse à l’intérieur de la partie basale de la Formation de Joggins et elle recouvre la Formation de Boss Point. Les strates étudiées sont cependant lithologiquement distinctes et on les reconnaît officiellement en tant que nouvelle Formation de Little River. Cette formation est limitée par des surfaces importantes à l’échelle régionale; on peut la retracer à l’intérieur des terres sur 30 kilomètres à partir de son stratotype de l’anse Lower. Une analyse du faciès révèle qu’il représente les dépôts d’une plaine alluviale bien drainée, sectionnée par des rivières peu profondes caractérisées par des crues éclair. On peut nettement la distinguer de la Formation sous-jacente de Boss Point (division 6 de Logan), grâce à ses canaux beaucoup plus petits, ainsi que de la Formation sus-jacente de Joggins (division 4 de Logan), par l’absence de couches houillères et de couches de calcaire abritant des lamellibranches. Les assemblages palynologiques révèlent que la Formation de Little River remonte probablement à la période du Namurien tardif au Westphalien basal (Langsettien basal) et qu’elle constitue vraisemblablement un équivalent chronologique de la Formation officieuse de Grande-Anse dans le sud-est du Nouveau-Brunswick.
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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 | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".