U-Pb geochronology reveals that hydrothermal dolomitization was coeval to the deposition of the Burgess Shale lagerstätte
Bibliographic record
Abstract
Abstract Fault-controlled, hydrothermal dolomitization often occurs at margins between shallow-water carbonate platforms and deep-water sedimentary basins. In western Canada, for example, the platform margin between the Cathedral Formation and the Burgess Shale Formation has been dolomitized at temperatures up to ~200 °C, with local magnesite, talc, and clinochlore mineralization. At the same time, the Burgess Shale Formation includes exceptional fossils that provide key evidence of the radiation of the animal phyla during the Cambrian Period (541 to 485.4 Ma). This lagerstätte and Mg-rich minerals within the adjacent and underlying strata, however, have been critically understudied. Here we show, using carbonate U-Pb geochronology, that western Canada was tectonically active and subject to hydrothermal dolomitization during the Middle Cambrian (Miaolingian Epoch) to Middle Ordovician (488.1 ± 18.8 Ma). These results extend the latest stages of rifting along the western margin of Laurentia into the Paleozoic, while also suggesting that the dolomitization of the Cathedral Formation occurred at the same time as the deposition of the Burgess Shale lagerstätte.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".