Post-Paleocene cooling in the southern Canadian Atlantic region: evidence from apatite fission track models
Bibliographic record
Abstract
The traditional view of the geomorphic evolution of the southern Canadian Atlantic margin is one of gradual exhumation and peneplanation following TriassicJurassic rifting. Thermal modelling of apatite fission track data from pre-Carboniferous granitic basement in Nova Scotia and from Permian and Triassic sandstones from Nova Scotia, New Brunswick, and Prince Edward Island suggest a more complex thermal evolution of the onshore part of the margin. Models clearly indicate significantly elevated regional paleotemperatures during Jurassic time, and as much as 30 °C of post-Paleocene cooling. Model-predicted paleogeothermal gradients for granitic samples from the Digby D-1 well are normal, ranging from 15 to 20 °C/km. Post-Paleocene cooling may be attributable to the combined effects of 13 °C of exhumational cooling from erosion of approximately 700 m of post-Aptian sediments caused by decreased eustatic sea levels, and 817 °C of cooling from the propagation to depth of a 1020 °C decrease in paleo-mean annual surface temperatures between Late Cretaceous time and the present. The combined effects of burial heating related to increased eustatic sea level and the propagation to depth of higher paleo-mean annual surface temperatures in the Late Cretaceous may also explain elevated vitrinite reflectance levels in Cretaceous lignites and in Jurassic strata in the Fundy Basin of Nova Scotia. These models demonstrate that the traditional view of passive peneplanation and slow exhumation of the margin since Early Jurassic time is not tenable.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| 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".