Bibliographic record
Abstract
The global extinctions linked to the Cretaceous-Tertiary (K-T) boundary severely affected marine pelagic organisms. The K-T boundary intervals at Deep Sea Drilling Project (DSDP) Site 527 (Leg 74) in the South Atlantic Ocean and Site 465 (Leg 62) in the Pacific Ocean were studied for changes in calcareous nannofossil assemblages from the late Maastrichtian to the early Paleocene. The sections analysed cover 180 kyr of the terminal Cretaceous and 200 kyr of the earliest Tertiary. Absolute and relative abundances of calcareous nannoplankton were calculated for both the entire flora and for individual species. No decrease in the number of species occurs towards the K-T boundary; relative and absolute abundances of different species are fairly stable throughout the terminal 180 kyr of the Cretaceous. At the K-T boundary the calcareous nannoflora shows a drastic and instantaneous decrease in absolute abundance. Typical Cretaceous species became extinct at the K-T boundary, but are present in the lowermost Tertiary as a result of bioturbation and reworking of the sediments. Very few species survived the K-T boundary. The species that occur sporadically in extremely low numbers in the Cretaceous, exhibit stable relative and absolute abundances through the lower Tertiary. Evolving Tertiary species appeared at the boundary and vary only moderately in absolute abundance through the lowermost Paleocene. The productivity of calcareous nannoplankton is determined here as the nannofossil accumulation rate (NFAR), which is suggested as an estimate of surface-water primary productivity. The terminal Cretaceous NFAR values were high and stable. At the K-T boundary the calcareous nannoflora suffered a 70-150-fold decrease in NFAR, indicating a catastrophic event. The Tertiary NFAR values remained low and fairly constant through the first 200 kyr. The productivity of calcareous nanno- plankton in the earliest Tertiary was dominated by the calcareous dinoflagellateThoracosphaerasp.
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.005 | 0.002 |
| Meta-epidemiology (broad) | 0.003 | 0.003 |
| Bibliometrics | 0.005 | 0.003 |
| Science and technology studies | 0.003 | 0.003 |
| Scholarly communication | 0.006 | 0.010 |
| Open science | 0.007 | 0.006 |
| Research integrity | 0.009 | 0.004 |
| Insufficient payload (model declined to judge) | 0.993 | 0.995 |
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; the direct Gemma label and the distilled Codex classifier agree on what is shown here.
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".