Chemo-biostratigraphy of the Dzabkhan Craton: Refining the Ediacaran-Cambrian Transition in Southwestern Mongolia
Bibliographic record
Abstract
The Ediacaran-Cambrian (Ed-C) transition is recognised as a globally significant juncture, with sedimentary records found across numerous cratons worldwide. Here we report a sedimentary sequence from the Dzabkhan micro-continent in SW Mongolia, spanning the late Ediacaran-Cambrian Stage 3 interval, revealing several major positive and negative C isotope excursions and interpret the first excursion as the onset of the basal Cambrian carbon isotope excursion (BACE). Our study comprehensively discusses synchronous stratigraphies from Mongolia, Kazakhstan, South China, Tarim, Siberia, Morocco, and Newfoundland. Most records consistently exhibit a distinctive pattern that includes the first appearance datum (FAD) of Small Skeletal Fossils, negative carbon isotope excursions, and strontium isotope uptrends. While the Ed-C boundary is defined by the FAD of ichnospecies Treptichnus pedum , the appearance of this ichnospecies is limited to siliciclastic environments and is diachronous between regions. Meanwhile, other bio- or chemostratigraphic signatures have also been considered as auxiliary markers to define the base of the Cambrian. Therefore, the small skeletal fossils Protohertzina anabarica , P. unguliformis and Anabarites trisulcatus , strontium and carbon isotope excursions are here utilized as potential supplementary diagnostic tools. Furthermore, our palaeoenvironmental reconstructions elucidate the variations in carbon and strontium isotope trends spanning this period, which may reveal carbon cycling and tectonic processes during sedimentation on the Dzabkhan Craton. These environmental changes may further support redefining the boundary.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 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".