C and O Isotope Composition of the Neoproterozoic Pre-, Syn-, and Postglacial Carbonates: Evidence from the Longdor Uplift and Western Slope of the Aldan Shield, Southern Siberian Platform
Bibliographic record
Abstract
Abstract New data on the C and O isotope composition in the Neoproterozoic carbonates of the Ballaganakh and Dal’nyaya Taiga regional stages (southeastern margin of the Patom paleobasin (hereafter, Basin) are presented. The negative δ13С anomaly, established in the upper part of the Ballaganakh regional stage, is comparable (in amplitude and stratigraphic position) to the Trezona anomaly, which preceded the Marinoan glaciation. The carbonate layers in glacial deposits of the Nichatka Formation of the Dal’nyaya Taiga regional stage have moderately positive δ13С values. The dolomite unit at the postglacial sequence base is characterized by moderately negative δ13С values that are typical for the cap carbonate sequence associated with the end-Marinoan glaciation. The lower part of the postglacial sequence (Barakun Formation) is characterized by a gradual increase of calcite in the carbonate component of rocks and a shift in the isotope composition corresponding to the difference in the fractionation coefficient of stable C and O isotopes for dolomite and calcite. This phenomenon, recorded in the postglacial sequences of Namibia and Canada as well, indicates that the carbonate mineral composition was governed by a global change in water chemistry rather than postsedimentary alteration. The overlying carbonate rocks of the Dal’nyaya Taiga regional stage in the epicontinental part of the Patom Basin (Sen Formation) are depleted in 13С compared to their shelf analogs in the Ura Uplift. Probably, the carbonates were accumulated asynchronously in the epicontinental and shelf facies of the Patom Basin. The reconstructed trend of variations in the carbon isotope composition for the Dal’nyaya Taiga regional stage is characterized by positive and low-amplitude negative δ13С anomalies similar to those in the Doushantuo Formation (China).
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| 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".