Do we really know Apex Chert? Newly identified micro- and dubiofossils
Bibliographic record
Abstract
Now at : Institut du Physique du Globe, 4 place Jussieu 75252 Paris cedex 05, France (clement@ipgp.jussieu.fr) The 3465 Ma old Apex Chert is probably the most studied Precambrian rock to date, since carbonaceous filaments, interpreted as cyanobacteria, were found more than two decades ago [1]. The occurrence of microfossils has been recently contested on the basis of the mineralogy of the sample and the carbon isotopes of the filaments, which suggests an inorganic, hydrothermal origin for the carbon [2]. Apex Chert has been studied with the most advanced techniques in microscopy and geochemistry, yet there are not evidences of other bacteriomorph structures than the carbonaceous filaments above mentioned. We analyzed a slightly polished section of Apex chert using a HITACHI S-4300SE/N with field effect scanning at variable pressure at GEOTOP. The sample was collected at the « Schopf Locality » at Chinnaman Creek, Pilbara Craton, Western Australia. SEM-EDX analyses allowed identifying euhedral and anhedral barite; native metals containing Zn, Cu and As; rare euhedral Ca-aluminosilicates; jarosite-alunite. The observed mineral assemblage is consistent with an hydrothermal origin of the chert [2]. We observed isolated sinuous flatted silica filaments and clusters of silica needles (0.1 µm wide; 2 µm long). Silica needles have rounded extremities, smoothed surfaces and several among them show an open tube in the centre. These morphologies are similar to those observed during encrustation of unsheathed microbes by amorphous silica. More interesting, we found ramified, sinuous, tubular structures in cavities previously occupied by sulfates (likely jarosite-alunite). These morphologies look similar to cyanobacterial mats observed in Paleozoic jaspilites. We cannot yet decipher if these silica structures are syngenetic to Apex Chert or of secondary origin. However, these results clearly show that Apex Chert has not yet completely revealed its content and new investigations are neded to resolve its origin. [1] Schopf (1993)
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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 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".