First High‐Precision U–Pb CA–ID–TIMS Age of the Chuanlinggou Formation, North China Craton: Implications for Global Correlations of Black Shales and the Statherian/Calymmian Boundary
Bibliographic record
Abstract
Abstract The Chuanlinggou Formation in the northern North China preserves the world's earliest multicellular eukaryote microfossils. Here we present a high‐precision zircon U–Pb CA–ID–TIMS age of 1,641.7 ± 1.2 Ma for a tuff layer within the black shales of the Chuanlinggou Formation. The new age is similar to those obtained for black shales from the Cuizhuang Formation in the southern North China, and the Barney Creek and Fraynes formations in the North Australia, indicating synchronous deposition of large volumes of black shales across both the North China and North Australia at ca. 1640 Ma. Global correlations and analysis of the spatial distribution of ca. 1640 Ma black shales and large igneous provinces (LIPs) and associated magmatic rocks in paleogeographic reconstruction reveal a spatiotemporal link between the ca. 1640 Ma LIPs and black shales. The widely distributed ca. 1640 Ma LIPs and black shales in Columbia supercontinent can provide a natural marker for the Statherian/Calymmian boundary at 1,640 Ma.
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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 | 0.000 | 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".