Volcanic ash in the Lower Cretaceous Chaswood Formation of Nova Scotia: source and implicationsGeological Survey of Canada Contribution 20100082.
Bibliographic record
Abstract
Lignites and coals, because of their low sedimentation rates of terrigenous detritus, may preserve a record of volcanic ash fall. Lignite from the Lower Cretaceous Chaswood Formation in central Nova Scotia was studied to identify whether any volcanic ash is present and can be correlated to known Early Cretaceous volcanism in southeastern Canada and adjacent New England. The bulk mineralogy and geochemistry of lignite and lignitic mudstones was determined by X-ray diffraction and whole-rock geochemical analysis of ashed samples; selected samples were examined by electron microprobe and scanning electron microscope. Much of the terrigenous component of some lignites consists of detrital sediments. In some lignites, distinctive rare earth element patterns are due to leaching from monazite and concentration in organic matter. Some lignites, however, lack illite and (or) quartz indicative of detrital sources, but show unusual abundance of stable high-field-strength elements such as Nb, Ta, and Hf, suggesting a volcanic source. Wood or charcoal fragments appear mineralized and diagenetic talc is present. Most of any ash component has been altered to kaolinite. Bulk composition of original ash ranges from basaltic to rhyolitic and matches chemically with subalkaline volcanic rocks on the SW Grand Banks and Orpheus graben. Coeval volcanic rocks on the U.S. continental margin and the New England–Quebec igneous province are more alkaline. Altered ash in lignite in the lower member of the Chaswood Formation correlates with Neocomian volcanism on the SW Grand Banks; and in the middle and upper members with Aptian–Albian volcanism in Orpheus graben.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".