The first continuous late Pleistocene tephra record from Kamchatka Peninsula (NW Pacific) and its volcanological and paleogeographic implications
Bibliographic record
Abstract
Highlights \n \n• First continuous MIS 2 explosive eruptions record from the Kamchatka volcanic arc. \n• 25 major tephra markers with a potential for regional and hemispheric correlations. \n• The largest (M ≥ 6.5) eruption originated from the Gorely eruptive center ∼28 ka BP. \n• The high quality geochemical data for over 70 tephra layers. \n• A newly proposed large glacial paleolake system in the Central Kamchatka Depression. \n \nAbstract \n \nThe Kamchatka volcanic arc (NW Pacific) is one of the most productive arcs in the world, known for its highly explosive activity. At the same time, the Kamchatkan record of late Pleistocene explosive eruptions has remained fragmentary. Here we present the first continuous record of Kamchatkan explosive activity between ∼12 and 30 ka, which includes ∼70 eruptions and extends the earlier reconstructed Holocene sequence for another 20 ka. Our record is based on geochemical correlations of 14C-dated tephras that represent all Kamchatka volcanic zones and are buried in lacustrine deposits along the 200 km stretch of the Central Kamchatka Depression (CKD). The accompanying geochemical database of volcanic glass compositions includes 3104 new electron microprobe and 221 LA-ICP-MS analyses. The data show that during the period under study, large silicic explosive eruptions peaked at 30–25 ka. Later times were mostly associated with moderate activity from northern CKD volcanoes Shiveluch and Zarechny. Our tephra record provides the first tephrochronological model for dating and correlating Central Kamchatka late Pleistocene deposits and gives us some insight into the timing of glacial advances in the Kliuchevskoi volcanic group and volcanic response to the onset of the Last Glacial Maximum and glacial unloading at its termination. In addition, studied sections of lacustrine deposits tightly linked by tephra markers suggest the existence of a large lake system within the CKD for ∼20 kyr until its final discharge at ∼12 ka BP.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".