Alluvial facies evolution during the Palaeozoic greening of the continents: case studies, conceptual models and modern analogues
Bibliographic record
Abstract
Abstract The Palaeozoic greening of the continents – the appearance and expansion of embryophytes (land plants) in terrestrial environments – was arguably the most fundamental Phanerozoic change to the Earth system. Thirteen case studies of Cambrian to Devonian fluvial deposits from North America and Europe are documented here to illustrate the evolution of fluvial style during this period. During the Cambro‐Ordovician, prior to the advent of terrestrial vegetation, fluvial systems laid down relatively coarse sands with little mud, resulting in self‐formed channels and an architecture dominated by broad sheets of trough cross‐beds (sheet‐braided style). Similar deposits formed across a wide range of latitudes, and passed basinward into sandy coastal deposits. From the mid Ordovician onwards, an increase in floodplain mudstone corresponds broadly with the appearance of embryophytes, which would have progressively enhanced upland weathering, mud production and floodplain storage of fines. During the Late Silurian, small heterolithic channel bodies with lateral‐accretion sets provide the first evidence of meandering channels, and floodplain mudstones contain more varied palaeosols, especially calcretes which appear abundantly for the first time. By the Early Devonian, channel deposits comprise sandstone lenses (channelled‐braided style), probably due to the increased bank strength and cohesion and reduced potential for sediment sorting imparted by sand‐mud mixtures. Muddy coastal deposits are prominent. By the Upper Devonian, fluvial deposits commonly contain fossil trees and large mainstem meandering channels with lateral‐accretion sets, indicating that rooted vegetation stabilized channels. The advent of stable floodplains with levées, crevasse splays and organic litter would have encouraged the diversification of terrestrial invertebrates, which left alluvial ichnological signatures from the Late Silurian onwards.
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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 | 0.003 |
| Science and technology studies | 0.001 | 0.002 |
| 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".