Geochemistry of the Eocene clastic sediments (Suonahu Formation) in the North Qiangtang Basin, Tibet: implications for paleoclimate conditions, provenance and tectonic setting
Bibliographic record
Abstract
The geochemistry of the clastic sedimentary units of the Suonahu Formation from the QD17 well in the northern Qiangtang basin, Tibet, was studied using various chemical analyses. SiO 2 /Al 2 O 3 ratios indicated that compositional maturity and recycling of the sediments were low to moderate. The total rare earth element (∑REE) contents of the clastic sediments ranged from 29.28 to 191.92 ppm. Element abundances suggest that the studied clastic sediments in the northern Qiangtang Basin were mainly sourced from felsic rocks mixed with small amounts of intermediate rocks, and that they were mostly developed in a continental setting. The REE geochemistry of the clastic sediments suggests that these different lithological samples were derived from a similar terrigenous source and that the Eu anomaly was inherited from the source rocks. The paleoclimate index (C-value) varied from 0.01 to 0.36, reflecting generally arid to semiarid conditions. In addition, Rb/Sr (about 0.41) and Sr/Cu (about 37.02) ratios support the idea that arid conditions prevailed during the deposition of the Suonahu Formation. Sr/Ba ratios (0.48–3.23) suggest a paleoenvironment with variable salinity. The covariation among this factor and paleoclimate indicators suggests that variations in climatic conditions exerted a primary control on salinity. The chemical index of alteration (CIA), A–CN–K ternary diagram, and low Th/U ratios indicate that the parent rocks of the clastic sediments experienced weak chemical weathering. Two multidimensional tectonic discrimination diagrams based on major elements show that the Suonahu Formation was deposited in a rift-related basin. The TiO 2 versus Zr, La/Th versus Hf, and Co/Th versus La/Sc bivariate diagrams and multi-major elements discrimination diagram indicate that the detritus was primarily derived from felsic igneous rocks with less contribution from intermediate igneous rocks.
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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 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| 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".