Paleoecology of Early Pennsylvanian vegetation on a seasonally dry tropical landscape (Tynemouth Creek Formation, New Brunswick, Canada)
Bibliographic record
Abstract
Abstract The distribution and community ecology of Early Pennsylvanian (middle Bashkirian, Langsettian) vegetation on a seasonally dry fluvial megafan is reconstructed from plant assemblages in the Tynemouth Creek Formation of New Brunswick, Canada. The principal motif of the redbed-dominated succession consists of degraded interfluve surfaces overlain by coarsening-upward aggradational sequences, a pattern that expresses the approach of an active channel system over a part of the megafan where landscape stasis prevailed. Accrual under a (dry) subhumid tropical climate, typified by a protracted dry season and a short wet season with torrential rainfall, resulted in Vertisol-like paleosols, episodic discharge and sedimentation, shallow channels incised into partially indurated interfluve strata, and scattered 'waterhole' deposits. Plant fossils, including many upright stumps, are preferentially preserved above paleosol-mantled interfluve surfaces, recording the inundation of a vegetated landscape. Quantitative analysis of 41 census-sampled megafloral assemblages collected in facies context indicates that a cordaitalean-rich flora dominated the dryland ecosystem. Less common was a wetland flora typical of tropical lowlands at coeval localities, comprising medullosalean pteridosperms and calamitaleans with rare ferns and lycopsids. 'Enigmatic dryland' plants, taxa of ambiguous affinity including Megalopteris, Pseudadiantites, and Palaeopteridium, were rare but surprisingly diverse. The taphonomic and sedimentologic context of fossiliferous horizons indicates that low-diversity, old-growth stands of gigantic cordaitaleans blanketed distal interfluves and inactive parts of the megafan, environs marked by limited deposition and extended paleosol development. Small patches of the pteridosperm-dominated wetland flora were interspersed within the dense cordaitalean forest, restricted to landforms that acted as waterholes during the dry season, such as perennial lakes, stagnant ponds, and seasonally active interfluve channels. In contrast, cordaitaleans and wetland plants formed mixed communities in disturbance-prone proximal interfluves and fluvial tracts, where more flooding and sedimentation resulted in less moisture-stressed conditions and a wider range of habitable landforms. Dense calamitalean groves persisted alongside fluvial channels, and an array of wetland plants occupied seasonally active abandoned channels that retained water throughout the year (waterholes). Rare 'enigmatic dryland' species were more prevalent in flood-prone fluvial tracts, and were dispersed within cordaitalean-dominated and wetland communities rather than forming discrete, compositionally unique patches. Although frequently characterized as 'extrabasinal' or 'upland' elements, this study confirms that these unusual plants occupied Pennsylvanian tropical lowlands during episodes of climatic drying.
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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 | 0.002 | 0.003 |
| 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".