Radiogenic and Stable Sr Isotope Records Preceding the Sturtian Snowball Earth Event
Why this work is in the frame
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Bibliographic record
Abstract
Large negative 13 C excursions precede global glaciations in the Neoproterozoic, but causal mechanisms remain unknown. To address this problem, we used a high-precision TIMS method 1 to measure radiogenic and stable strontium isotope ratios ( 87 Sr/ 86 Sr and 88/86 Sr) in carbonate rocks composing the Copper Cap Formation (Mackenzie Mountains, Canada), which was deposited prior to the Sturtian glaciation (~717 -662 Ma) 2 . With these data, we aim to understand how chemical weathering, hydrothermal alteration, carbonate burial, and other factors contributed to environmental change during the ~25 Myr runup to the first Snowball Earth event. 87 Sr/ 86 Sr and 88/86 Sr range from 0.706 to 0.714 and 0.30 to 0.51. All 88/86 Sr are higher than the average for Phanerozoic carbonates 3 . Above ~250 m, 87 Sr/ 86 Sr ranges between 0.7064 and 0.7068. The two proxies appear to positively covary to ~300 m but diverge thereafter. Relatively high 87 Sr/ 86 Sr below ~250 m may indicate late-stage diagenetic overprinting. Further work will be done to investigate the effect of diagenesis on these values by examining the paragenetic history of the carbonate rocks. A coupled 87 Sr/ 86 Sr and 88/86 Sr model will be constructed to better understand what mechanisms, whether primary or secondary, drove the observed signals.
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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 | 0.001 | 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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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 it