Stratigraphy of Triassic-Jurassic boundary sequences from the Kawhia coast and Awakino gorge, Murihiku Terrane, New Zealand
Bibliographic record
Abstract
We have examined the stable carbon isotope stratigraphy, bio- and litho-stratigraphy of the Upper Triassic (Otapirian) - Lower Jurassic (Aratauran) boundary strata from the Awakino gorge and Kawhia coast sections, Murihiku Terrane, North Island, New Zealand. Successive occurrences of species of the bivalve genus Otapiria, O. dissimilis, O. marshalli and O. aff. marshalli, and also of age diagnostic ammonites indicate that the Hettangian strata in both sections are very thin compared with the Rhaetian sequences. Lamination structures are well developed at the Tr-Jr (Rhaetian- Hettangian) boundary transition interval. The δ: 13 values of organic matter from siltstone and carbonate nodules in the sedimentary rocks range from -28.5 to -25.5%o and there is no correlation between δ: 13C and C/N ratios. The excursion patterns of δ: 13Corg from both sections are similar, showing a negative spike at the uppermost Rhaetian and a positive spike immediately below the Tr-Jr boundary. A long-lived positive shift is also recognized in the Awakino gorge section, which coincides in pattern with those reported in Tr-Jr boundary successions from the Queen Charlotte Islands, British Columbia, Canada. These results suggest that although magnitude and absolute values are slightly different, the integrated pattern of stable carbon isotope signatures over the Tr-Jr boundary could be a valuable tool for correlation, at least between sedimentary rocks from similar depositional settings in the Panthalassa.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".