Biosedimentology of the Early Jurassic post‐extinction carbonate depositional system, central High Atlas rift basin, Morocco
Bibliographic record
Abstract
Abstract This study documents a Liassic example of the long‐ranging effects of mass extinction on carbonate systems. Biohistoric constraints inherent in the Liassic carbonate depositional system are deciphered from normal‐marine, sub‐tidal deposits of the central High Atlas rift basin (Morocco) through ?Hettangian/Sinemurian to Early Toarcian times. The integration of results from the analysis of lithofacies, depositional geometries, microfacies, macrobenthos, carbonate build‐ups, carbon and oxygen stable isotopes, and rare earth element + yttrium distribution patterns allows the intrinsic (or biohistoric) control on the central High Atlas deposits to be separated from extrinsic factors, such as basin development and palaeoclimate. The survival interval in the aftermath of the end‐Triassic mass extinction persisted until the Early Sinemurian indicated by a severely depleted carbonate system impoverished in skeletal organisms. A tectonic pulse at the Early to Late Sinemurian boundary interval caused a basin widening with immigration of a marine fauna. However, until the latest Sinemurian (macdonelliSubzone of theraricostatumZone) the deposits were dominated by filter‐feeding benthic heterotrophs (sponges, brachiopods, polychaetes and crinoids). During this stage, primary production within the enlarged basin must have been largely planktonic and there was a net‐flux of organic matter to the sea floor (oxygen minimum zone). A regional radiation of organic‐walled phytoplankton is inferred to explain the selective success of the filter‐feeding community and the occurrence of sponge mounds. Thus, significant effects of the end‐Triassic mass extinction are still present during the Late Sinemurian. Through almost the entire Pliensbachian a highly productive, shoal‐rimmed carbonate platform existed; it developed subsequent to tectonic reorganization and a marine recirculation event (radiolarian facies, Δδ13C ≈ −1·1, strongly negative Ce‐anomaly). Photosymbiotic sediment producers (mainly large bivalves) now state the success of specialists and environmental equilibrium conditions. In the latest Pliensbachian the climax stage was reached with the development of a coralgal reef‐rimmed carbonate platform. The Liassic carbonate depositional system experienced a terminal, multicausal Early Toarcian drowning event during which most of the large bivalves became extinct.
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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 | 0.002 | 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) | 0.002 | 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".