Magnetic Anisotropy and the Paleosecular Variation Record in Stalagmites from Njirak Cave, East Java: The Effect of Detrital Magnetite Emplaced in Small Cavities by Flooding Events
Bibliographic record
Abstract
Magnetic anisotropy and remanence were measured for 33 samples from the axis of two stalagmites from Njirak Cave in East Java. All 33 samples were stepwise demagnetized with alternating fields, but only 16 were stable enough to yield reliable characteristic remanence directions. These directions differ, especially in declination, from the present Earth’s field direction and agree for samples of about the same age from both stalagmites, suggesting that the Earth’s field at Njirak Cave maintained a declination averaging 23° and an inclination averaging −23° for most of the past 2,500 years. Anisotropy of magnetic susceptibility is high, averaging 5.8%. The minimum susceptibility axes are nearly horizontal with scattered declinations; whereas the maximum susceptibility axes tend to be steeply inclined (average inclination is 51°). This implies that the long axes of the mainly multi-domain magnetite grains tend to be steeply inclined (rather than horizontal, as expected if the magnetite were in horizontal detrital layers). We suggest that this is due to the magnetite being in flood-emplaced detritus adhering to the steeply-inclined sides of small (2 to 5 mm) cavities that cut across and are sealed off by the stalagmites’ horizontal calcite growth layers. Steeply inclined maximum susceptibility axes should help detect such stalagmites, whose quality of paleosecular variation record may be lowered by magnetite-bearing cavities.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".