Increasing Tephra Deposition in Northeastern North America Points to Atmospheric Circulation Changes at the Early Mid Holocene Transition
Bibliographic record
Abstract
Abstract The number of cryptotephra (non‐visible volcanic ash) records from northeastern North America is unique in the continent. The resulting tephrostratigraphic framework includes ash deposits sourced from volcanic arcs across the Northern Hemisphere and is an exceptional resource for correlating and dating paleoenvironmental records. It also provides an opportunity to explore more novel questions regarding the controls on ultra‐distal tephra (volcanic ash >3,000 km from source) dispersal and deposition. Here, we examine temporal patterns in the tephrostratigraphy of northeastern North America to test the legitimacy of a previously noted change in ash deposition frequency at the Early Mid Holocene transition. We integrate five new cryptotephra records into the existing framework to improve its temporal and spatial extent and report further occurrences of widespread cryptotephra deposits including Mt. St. Helens We, Jala pumice, White River Ash east, Ruppert tephra, Mt. St. Helens Yn and Mazama Ash. Reexamination of the combined tephrostratigraphy using breakpoint analysis shows a significant increase in the frequency of ashfall after ca. 9,000 (7,860–9,650) cal yr BP (calendar years before C.E. 1950). We discuss this change in relation to volcanic and environmental controls of fine ash dispersal and preservation. We reject hypotheses relating to eruption frequency or depositional processes in favor of changing atmospheric transport patterns and tephra dispersal—possibly caused by the retreat of the Laurentide Ice Sheet. Our study is a novel example of how tephrostratigraphy can be used beyond traditional correlative and dating studies, in this case indicating large‐scale changes in atmospheric circulation through time.
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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".