Eocene initiation of the Cascadia subduction zone: A second example of plume-induced subduction initiation?
Bibliographic record
Abstract
The existing paradigm for the major ca. 56–48 Ma subduction zone reorganization in the Pacific Northwest of North America is that: (1) the Siletzia large igneous province erupted offshore to the west of North America, forming an oceanic plateau; (2) Siletzia then collided with North America, clogging the Pacific Northwest segment of the Cordilleran subduction zone; and (3) the oceanic lithosphere west of Siletzia then ruptured to initiate the new Cascadia subduction zone. Oceanic lithosphere is strong and difficult to rupture, so this would represent a rare example of such a rupture initiating a new subduction zone. This paper explores an alternative hypothesis for the reorganization, a plume-induced subduction initiation (PISI) mechanism, which has previously been applied to the initiation of Caribbean plate subduction zones in the Cretaceous. In this PISI hypothesis, a newly formed, ∼1200-km-diameter Yellowstone mantle plume head rose at ca. 55 Ma beneath western North America, generating Siletzia in situ on the North American margin, as well as generating the ∼1700-km-long Challis-Kamloops volcanic belt ∼600 km to the east of Siletzia. This destroyed the existing Cordilleran subduction zone and allowed the new Cascadia subduction zone to form by collapse of thermally weakened oceanic lithosphere over the hot western margin of the plume head. This PISI hypothesis provides an integrated framework for understanding Siletzia, the Challis-Kamloops belt, Eocene core complexes from Idaho (U.S.) to British Columbia (Canada), underplated mafic rocks beneath Oregon and Washington (U.S.), post–17 Ma manifestations of the Yellowstone plume, and geophysical characteristics of the lithosphere beneath the Pacific Northwest.
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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 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".