Paleosecular Variation, Geochronology, And Magnetic Mineralogy Of Pleistocene Igneous Rocks Of Ascension Island, South Atlantic Ocean
Bibliographic record
Abstract
Paleomagnetic samples were collected from 68 sites on Ascension Island between May 14 and June 18, 2001. Paleomagnetic analyses of samples were performed at the University of Puget Sound paleomagnetic laboratory. Preliminary results indicate that 32 sites yield normal directions, six sites give reversed directions, and three sites exhibit intermediate directions (VGP latitude less than 60°). Eight sites exhibit too much scatter in paleomagnetic directions to be useful and nineteen sites have yet to be analyzed as of 9/1/02. Mean directions for both normally and reversely magnetized units tend to exhibit inclinations steeper than expected for Ascension Island. Ar/Ar dating of 20 samples was completed at the University of Wisconsin, Madison. Ages range from 50.9+/-7.9 ka to 1086.2+/-15.2 ka. Ages and polarities indicate directions represent the Matuyama Chron, Brunhes Chron, and Jaramillo Subchron. Sixteen samples from twelve sites were examined using reflected light microscopy at Tarleton State University. Eight sites appear to be relatively unaltered. Three sites show moderate alteration, but appear to retain substantial primary magnetic mineralogy and record primary magnetic directions. One site is extensively altered and probably records secondary magnetism. Optical examination confirms inferences from thermal demagnetization that magnetic mineralogy is largely dominated by titanomagnetite with some units containing significant hematite. A substantial paleosecular variation (PSV) database has been compiled for the past 5 Ma, but numerous areas, including the South Atlantic are underrepresented. This study has produced enough magnetic directions from the last million years or more to fill a gap in the PSV database, which can be used to test and refine emerging geodynamo models.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".