Paleomagnetic evidence for 50 m.y. of tectonic rotations in the Junggar block driven by far-field effects of the India-Eurasia collision
Bibliographic record
Abstract
Abstract The tectonic history of the Junggar block, one of the largest tectonic units within the Central Asia orogenic belt, is pivotal for understanding the geodynamic processes associated with the India-Eurasia collision. Despite recurrent compressional deformation along numerous faults during the Mesozoic and Cenozoic, the magnitude of Cenozoic tectonic rotations in the Junggar block relative to Eurasia remains poorly constrained. To assess such rotations quantitively, we present paleomagnetic data from the Cenozoic sedimentary rocks in the Zaysan Irtysh zone in the northern part of the Junggar block. Stepwise thermal demagnetization revealed a high laboratory unblocking temperature component, interpreted as primary magnetization based on a positive reversal test. Seven mean directions were calculated for age intervals of 45–40 Ma, 42.5–37.5 Ma, 40–35 Ma, 37.5–32.5 Ma, 35–30 Ma, 25–20 Ma, and 22.5–17.5 Ma. The observed declination variations indicate a local counterclockwise rotation of 18.8° ± 11.4° between 40 ± 2.5 Ma and 35 ± 2.5 Ma. Comparison of these results with 23–3.1 Ma paleomagnetic data from the southern Junggar block obtained in previous studies suggests successive local counterclockwise rotations in the block's northern and southern regions. At a larger scale, the Central Asia right-slip fault zone experienced two stages of tectonic rotation (ca. 60–30 Ma and 25–5 Ma) driven by the far-field effects of the India-Eurasia collision and strike-slip faulting that propagated through intracontinental settings. These insights have broad implications for the tectonic evolution of intracontinental systems, extending beyond Central Asia to other orogenic belts and collision zones worldwide.
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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) | 0.002 | 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".