Massive Deposition of Carbonate Nodules in the Hyperarid Northwest Qaidam Basin of the Northern Tibetan Plateau
Bibliographic record
Abstract
Abstract Concretionary nodule formation is a subaerial process common to both Earth and Mars. The resulting nodules contain information about particular paleoclimatic cycles. However, their genesis and the mineralogical and geochemical effects of climate change on nodule formation have not well constrained so far, limiting their applications to paleoclimatic reconstruction. Since the late Pleistocene, the Qaidam Basin in the northern Tibetan Plateau has been subjected to extreme drought, resulting in a vast area of playas with a diverse eolian morphology that resembles the surface of Mars. Recently, a massive carbonate nodule field was discovered on an ancient diluvial platform in the northwest Qaidam Basin. Detailed analyses revealed that an early period of aragonite precipitation (251 kyr before present) provided seeding material for the later growth of nodule bodies during a period of ∼100 kyr. The highly unstable hydrologic and geochemical conditions during this period led to the growth of high‐Mg calcite zones with varied elemental contents (e.g., Mn), crystal patterns, and porosity levels within the nodule bodies. The δ13C and δ18O values increased by 3‰ and 6‰, respectively, from the cores to the rims of the measured nodules. Rayleigh distillation model suggested that 50% of the H2O and 25% of the dissolved CO2 had been removed during nodule growth in response to the drought. These results show that nodules formed in hyperarid environments can record important hydrologic information, which may provide insights for paleo‐environment studies on Mars by examining the formation of nodules in Gale Crater.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".