A short-term, post-Lomagundi positive C isotope excursion at <i>c.</i> 2.03 Ga recorded by the Wooly Dolomite, Western Australia
Bibliographic record
Abstract
It is generally accepted that carbon isotope variations in seawater were muted between c. 2.06 Ga, after the end of the Lomagundi carbon isotope excursion (LCIE), and c. 1.3 Ga. Evidence is presented here that c. 30 myr after the end of the LCIE, the biogeochemical cycle of carbon experienced a short-term ( c. 2 myr), high-amplitude (up to +8.4‰ V-PDB) perturbation, recorded in the Horseshoe rift basin, Western Australia. The basin was initiated at c. 2.03 Ga with deposition of fluvial and shallow-marine sandstones, followed by the eruption of flood basalt, and culminated with the deposition of platform carbonates, and accompanying volcaniclastic and siliciclastic sediments (Wooly Dolomite). The Horseshoe rift basin during deposition of the Wooly Dolomite was fault-compartmentalized but connected to an ocean. Six depositional sequences make up the Wooly Dolomite. Sequence 1 records establishment of a carbonate platform conformably on basalt and coevally with volcaniclastic sedimentation. All other sequences have dominant carbonate-platform deposits and are unconformity-bounded. Sequence 3 contains a c. 57 m thick section with 13 C-enriched carbonates bracketed between carbonates with close to 0‰ carbon isotope values. Further high-resolution chemostratigraphic studies may reveal a more complex pattern of carbon isotope variations during the ‘boring billion years’, but without precise geochronology similar short-term carbon isotope excursions in carbonate successions could be incorrectly correlated to the LCIE. Supplementary material: Table 2 including chemical and isotopic data, sample locations and their position in Figure 8 is available at https://doi.org/10.6084/m9.figshare.c.2868055 .
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".