Extending the Late Holocene Tephrochronology of the Central Kenai Peninsula, Alaska
Bibliographic record
Abstract
Tephrochronology, the reconstruction of past volcanic ash deposition, provides a valuable method for dating sediments and determining long-term volcanic history. Tephra layers are highly numerous in Alaska, but knowledge of their occurrence and distribution is incomplete. This study expands the regional tephrochronology for the Kenai Peninsula of southcentral Alaska by investigating the tephrostratigraphy of two peatland sites. We located seven visible tephras and seven microtephras and investigated the particle size and geochemistry of the visible tephras. Radiocarbon dates were used to estimate the timescale of each core. Geochemical comparison showed that the visible tephras originated from late Holocene eruptions of Augustine, Crater Peak–Mt. Spurr, and Hayes volcanoes. Some of the tephras had been documented previously, and these new findings expand their known range. Others represent eruptions not previously reported, including a Crater Peak–Mt. Spurr eruption around 430 cal. BP. The results provide new tephra data for the region, illustrate the spatial heterogeneity of tephra deposition, and show the potential of microtephras for expanding the regional tephra record.
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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) | 0.001 | 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".