New palynological data from the Upper Ordovician of the Precordillera Basin, Argentina: A potential key for understanding the geological history of the Precordillera terrain
Bibliographic record
Abstract
Biostratigraphic data from the Precordillera Basin have traditionally been analyzed to contribute to the understanding of its biogeographic evolution as an allochthonous microcontinent accreted to the western Gondwanan margin in the Middle-Late Ordovician. The first palynological data from Late Ordovician units of the eastern Precordillera are incorporated in an attempt to better constrain the timing of the collision. The Las Vacas Formation has previously been assigned to the Sandbian (gracilis–bicornis zones). Chitinozoans from the Las Vacas Formation are poorly diversified. The basal part of this unit contains Lagenochitina sp. cf. baltica, previously recorded in the late Darriwilian of Precordillera and the late Darriwilian-early Sandbian of eastern Canada. The assemblages from its upper part contain primarily Spinachitina bulmani, Cyathochitina sp. cf. kuckersiana, Cyathochitina sp. aff. macastyensis, and Desmochitina minor form typica. The lower-upper part of this formation also yields Kalochitina multispinata. Acritarchs are poorly preserved and the few recognized genera are not biostratigraphically significant. Cryptospore findings contribute to the record of evidences for land plants in the Ordovician of Argentina and suggest that the upper part of the unit was deposited proximal to the shoreline. The lower part of the Trapiche Formation contains a few poorly preserved chitinozoans, acritarchs and algae (cf. Gloeocapsomorpha sp.), probably due to reworking of the material. The basal chitinozoan assemblage could indicate that the deposition of the Las Vacas Formation started during the Middle-Late Ordovician (late Darriwillian-basal Sandbian). Typical Katian chitinozoans from the uppermost part of the Las Vacas Formation indicate that these deposits would have reached the middle Late Ordovician. Palynological studies seem to be a useful tool to contribute to the biostratigraphic knowledge of controversial terrains, such as the Precordillera.
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| 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".