Palaeoecology of a conodont age-calibrated and spectacularly preserved bryozoan-brachiopod biostromal palaeocommunity from the Asselian of Carlin Canyon, Nevada, USA
Bibliographic record
Abstract
The Strathearn Formation is a carbonate-dominated succession cropping out in Carlin Canyon, northern Nevada. The upper part of this unit is mid-upper Asselian (Lower Permian), as determined by conodont biostratigraphy including Sweetognathus expansus, Streptognathodus constrictus, and Mesogondolella striata. At the study location, the Strathearn is fine-grained carbonate, dominated by a heterozoan assemblage of bryozoans, brachiopods and echinoderms that accumulated in a mid-ramp setting below a thermocline. The studied unit is highly fossiliferous with a silicified bryozoan assemblage dominated by ramose forms including trepostomids, cryptostomids, and cystoporids, and subordinate fenestrids. The matrix between bryozoan zoaria includes carbonate mud and peloids with some microbial fabric and minor quartz silt. Brachiopods are also found throughout, mostly in life-position. They include large and small productides and small rhynchonellide and spriferinide taxa, suggesting sparse and limited food resources. They are mostly free-living semi-infaunal taxa indicating the occurrence of soft substrates, but some forms are pedicle-attached. Biotic relationships within the palaeocommunity were dominated by competition among suspension-feeders that collected food in different tiers at a depth between fair-weather and storm wave base. Some bryozoans lie horizontal to bedding, but others have a vertical life-position. Overall, the degree of relief suggests that this unit represents multiple incipient biostromes that were never fully developed, as determined by numerous storms that are recorded as graded tempestites downslope. The assemblage is compared to others along the western and northwestern margin of Pangea. Storms, increasing turbidity, and climate change may have locally inhibited and limited long-term development of this suspension-feeding community.“I’d like to be, under the sea, in a bryozoan’s garden, in the shade” apologies to The Beatles.
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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 | 0.000 | 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".