QUANTITATIVE ANALYSIS OF TAPHOFACIES AND PALEOCOMMUNITIES IN THE EARLY CAMBRIAN CHENGJIANG <i>LAGERSTATTE</i>
Bibliographic record
Abstract
Abstract Detailed sedimentological and quantitative taphonomical analyses of 11,974 fossil specimens from an early Cambrian (Stage 3) Chengjiang-type deposit near Haikou, Yunnan, reveals significant relationships between the original depositional environments and the composition and preservation of their respective fossil assemblages. In general, the Maotianshan Shale is characterized by superimposed couplets of laminated background and thin event mudstone layers representing two distinct taphofacies, A and B, respectively. Fossils in taphofacies A consist predominantly of indeterminate organic elements and fecal or algal strings with few, poorly preserved, soft-bodied animals. Among those, disarticulated arthropods account for 84.3% of specimens (mostly isolated valves of Kunmingella douvillei) and 51.4% of species. Poriferans represent 7.4% of specimens and 22.9% of species. Fossils in this taphofacies have undergone significant pre- or syn-burial decay and represent limited time-averaged assemblages exhibiting low species richness. By contrast, taphofacies B contains greater numbers of species and specimens and better preserved soft-bodied animals. Taphofacies B represents mostly smothered organisms by distal tempestites. Arthropods are also dominant in taphofacies B, both in terms of species richness (41%) and abundance of specimens (44%). Poriferans, priapulids, lobopods, and brachiopods exhibit similar low species richness (6–8% each), but poriferans and lobopods are numerically rare, at around 1% each, whereas priapulids and brachiopods make up 26% and 24% of specimens, respectively. The arthropod Kunmingella douvillei (19%), the priapulid Cricocosmia jinningensis (19%), and the brachiopod Diandongia pista (18%) are the most abundant species in taphofacies B. Fossil assemblages in taphofacies A and B have similar recurrent and abundant species and similar temporal trends in evenness and richness, but taphofacies A captures only a portion of the species that are preserved in taphofacies B. These results suggest that the fossil assemblages present in both taphofacies represent a single local community subjected to two different taphonomic processes and imply similar recurrent environmental conditions within the section studied.
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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 | 0.005 | 0.004 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".