Carbonate production and reef building under ferruginous seawater conditions in the Cambrian rift branches of the Avalon Zone, Newfoundland
Bibliographic record
Abstract
Abstract The characterization of carbonate production on rift basins is critical for understanding the nucleation and demise of reefs in tectonically active areas. A new petrographic and mineralogical analysis of Cambrian strata from the Avalon Zone in Newfoundland, based on scanning electron microscopy – back‐scattered electron detector and Raman spectrometer analyses, facilitates recognition of several episodes of Terreneuvian–Miaolingian carbonate production and associated precipitation of ironstone and phosphorite. These distinct units mainly developed on uplifted rift shoulders and basaltic lava palaeoreliefs, and reflect amalgamated high‐energy events, interrupted by scouring discontinuities (diastems) commonly lined by phosphatized and ferruginized microbial crusts. Mud‐mounds, in contrast, nucleated under calm conditions episodically punctuated by high‐energy episodes, where scattered thromboid structures occur as both clotted textures and distinct calcimicrobes. Precipitation of hematite/goethite versus chamosite couplets, both occluding primary porosities and replacing interlaminae and cortices of oncoids and coated aggregates, point to marine substrates close to the Fe‐redox boundary. Upwelling of phosphate‐rich ferruginous hydrothermal waters contributed to the precipitation of ironstone and phosphate interbeds. Ferruginous waters related to penecontemporaneous hydrothermal activity, reflected by the record of synsedimentary fissuring and stockwork ore bodies, were delivered to confined rift‐related horst‐and‐graben settings, largely controlled by the development of specific Cambrian carbonate and associated ironstone facies. The influence of ferruginous waters necessarily affected the record of climatically sensitive evaporitic pseudomorphs, reefs/mounds and phosphorites, which are then not suitable criteria to discriminate palaeolatitude, as demonstrated by a comparison of low‐latitude to middle‐latitude margins fringing Baltica, and the Avalonian and Atlas – Ossa‐Morena – Northarmorican rift transects of West Gondwana.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.002 | 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".