Tuff life: Bioalteration in volcaniclastic rocks from the Ontong Java Plateau
Bibliographic record
Abstract
We report microscopic textural, geochemical, isotopic, and biomolecular evidence for microbial alteration of glass shards in a 337.7 m thick sequence of poorly sorted vitric and lithic tuffs recovered during Leg 192 of the Ocean Drilling Program on the Ontong Java Plateau. Petrographic analysis has revealed the highest density and variety of exceptionally preserved microbial alteration textures in the glass shards, when compared to previous studies of glassy pillow basalt margins from ocean crust and ophiolites. Two textural types of microbial alteration are commonly observed: tubular and granular. Tubular textures are characterized by well‐preserved, micron‐scale, tubular to vermicular, channel‐like features with both smooth and scalloped walls that commonly extend from a granular alteration interface rimmed by clay into unaltered glass. These channels are highly convoluted or twisted and in some instances bifurcate. Detailed scanning electron microscopy (SEM) images reveal the presence of delicate filaments and desiccated thin films with morphologies suggestive of a biogenic origin within the channels. Granular textures appear as solid bands, semicircles, or irregular patches of individual and/or coalesced spherical bodies with irregular protrusions into fresh glass. Microprobe X‐ray element maps show elevated levels of carbon, nitrogen, phosphorous, and potassium associated with the microbial alteration features. Bulk‐rock carbon isotope ratios of disseminated carbonates in tuffs preserving fresh glass are depleted (<−9‰), suggesting biologic fractionation. The presence of nucleic acids within the microbial alteration features has been confirmed though staining with ethidium bromide, a stain that specifically binds to double‐stranded DNA and RNA. The presence of DNA/RNA suggests that the biogenic features may be relatively recent and that microbes may be currently active.
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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) | 0.000 | 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".