Paleozoic–Mesozoic dispersal of Gondwana: Insights from detrital zircon geochronology of Lesser Himalaya strata, eastern Nepal
Bibliographic record
Abstract
Abstract Detrital zircon geochronology has rapidly evolved into a powerful tool for reconstructing the assembly and dispersal processes of supercontinents. Currently, the dispersal history of Gondwanaland remains highly controversial. Here we focus on detrital zircon geochronology of the Gondwana (Carboniferous–Permian Kokaha Diamictite and Jurassic–Cretaceous Sapt Koshi Formation) and post-Gondwana (Miocene Tamrang Formation) sequences of the Lesser Himalaya in eastern Nepal. Detrital zircon U-Pb dating results show that the Carboniferous–Permian sequence peaks at 544 Ma, 890 Ma, 1178 Ma, and 1752 Ma. Likewise, the Jurassic–Cretaceous sequence peaks at 531 Ma, 947 Ma, 1176 Ma and 1806 Ma along with a much younger peak at 123 Ma. Similarly, the Miocene sequence peaks at 526 Ma, 987 Ma, and 1740 Ma. Comparing these newly obtained ages with those of surrounding regions, we confirm that during the Carboniferous–Permian, the Indian continent was still connected to Gondwana. The U-Pb age distribution of the Kokaha Diamictite coincides with that of the Tethys Himalaya, which further suggests the possibility that this unit either shared the same provenance with or was recycled from the Tethys Himalaya. During the early Mesozoic, the Indian plate rifted from Gondwana and drifted northward, as evidenced by Triassic–Jurassic, rift-related magmatism along the Indian continental margin. Remarkably, there were significant inputs from the Rajmahal Basalt during deposition of the Jurassic–Cretaceous sequence. Besides, the Miocene sequence records a large number of zircons that closely resemble those of the Greater Himalaya, which implies that the Greater Himalaya may have already been uplifted and eroded by then.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".