Volcanic ash layers in Lake El'gygytgyn: eight new regionally significant chronostratigraphic markers for western Beringia
Bibliographic record
Abstract
Abstract. Ash layers from explosive volcanic eruptions (i.e., tephra) represent isochronous surfaces independent from the environment in which they are deposited and the distance from their source. In comparison to eastern Beringia (non-glaciated Yukon and Alaska), few Plio-Pleistocene distal tephra are known from western Beringia (non-glaciated arctic and subarctic eastern Russia), hindering the dating and correlation of sediments beyond the limit of radiocarbon and luminescence methods. The identification of eight visible tephra layers (T0–T7) in sediment cores extracted from Lake El'gygytgyn, in the Far East Russian Arctic, indicates the feasibility of developing a tephrostratigraphic framework for this region. These tephra range in age from ca 45 ky to 2.2 My old, and each is described and characterized by its major-, minor-, trace-element and Pb isotope composition. These data show that subduction-zone-related volcanism from the Kurile–Kamchatka–Aleutian Arc and Alaska Peninsula is the most likely source, with Pb isotope data indicating a Kamchatkan volcanic source for tephra layers T0–T5 and T7, while a source in the Aleutian Arc is possible for tephra T6. The location of Lake El'gygytgyn relative to potential source volcanoes (> 1000 km) suggests these tephra are regionally distributed over a large area. These deposits provide a unique opportunity to correlate the high-resolution paleoenvironmental records of Lake El'gygytgyn to other terrestrial paleoenvironmental archives from western Beringia and marine records from the western North Pacific and Bering Sea, and to move towards the development of a robust integrated framework between the continuous paleoclimatic records of Lake El'gygytgyn and other terrestrial and marine records in NE Eurasia.
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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 | 0.001 | 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".