Direct dating of Qaidam Basin stratigraphy, Northern Tibet
Bibliographic record
Abstract
The Qaidam Basin, the largest intermountain basin in Northern Tibet, has recently gained attention for a newly proposed depositional age, specifically for the Lulehe Formation (Fm). Two contrasting models currently exist: the traditional interpretation places its deposition during the Paleocene or Eocene, while more recent age models suggest deposition during the Oligocene. This significant conflict hampers understanding of the timing of activity of the surrounding fault systems, and the uplift and growth mechanism of the northern Tibet. In this study, we sampled tubular carbonate veins and abundant paleosol calcareous nodules from the Lulehe Fm. Using calcite U-Pb dating and clumped isotopes, we obtained an average age of 50.8 ± 2.8 Ma and formational temperatures of the nodules ranging from 39.6 ± 2.3 °C to 43.2 ± 3.4 °C in the Honggou section, and 28.2 ± 0.7 °C to 34.3 ± 4.2 °C in the Hongshan West section. Furthermore, by applying elevation-dependent isotopic and clumped temperature lapse rates, we reconstructed the paleoelevation of the Qaidam Basin during the early Eocene to be 1.6 ± 0.98 km. Our findings align more closely with the traditional stratigraphic framework of the Lulehe Fm, indicating that initial sedimentation in the Qaidam Basin occurred during the early Eocene. Moreover, we provide a quantitative estimate of the basin's paleoelevation during its early stage. While our data may suggest the possibility of southward growth in northern Tibet, alternative interpretations cannot be ruled out, and further research is required to better constrain the uplift patterns.
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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 | 0.000 | 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) | 0.001 | 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".