Oligocene and Miocene Volcanics in the Sedimentary Forearc of the Outer California Borderland
Bibliographic record
Abstract
Abstract The Outer Continental Borderland offshore southern California consists of an arkose-bearing accretionary prism or truncated forearc basin with two subsequent discrete periods of calcalkaline volcanism and a third prolonged period of alkaline seamount volcanism. The volcanics exhibit progressively less continental influence/contamination with time. The earliest period consists of calcalkaline lavas dated at 30 million years ago (Ma) that erupted prior to the Pacific–Farallon spreading ridge reaching the California margin. These are moderately contaminated by continental rocks. The second more widespread period of calcalkaline activity, from 16 to 18 Ma, consists of lavas ranging from basaltic andesite to rhyolite that generally experienced less continental contamination than the 30 Ma volcanics. The 16 to 18 Ma lavas apparently formed as a triple junction migrated along the margin, although the offshore lavas are not midocean ridge basalt–like, as expected if generated within a slab window. The third, even younger period of volcanic activity produced Rodriguez Seamount on the Patton Escarpment; Northeast Bank within the Outer California Borderland; and San Juan, San Marcos, Little Joe, Davidson, Guide, Pioneer, and Gumdrop Seamounts on the Pacific Plate. These youngest lavas, previously described in the literature, have little to no signature of continental contamination, although lavas that built Rodriguez and Northeast Bank migrated through continental crustal materials. These results are largely based on samples either dredged or collected via remotely operated vehicle from the seafloor. The widespread occurrence of erratics in our California Borderland sample set indicates that their presence must be weighed when reconstructing the geology of the region.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".