Environmental changes across the upper Eocene to upper Oligocene of the southern Labrador Sea, DSDP Site 112
Bibliographic record
Abstract
The Eocene Oligocene Transition (EOT) 34 million years ago (Ma), was characterized by a climate shift from a largely ice-free greenhouse world to an icehouse climate. The colder Oligocene period included several cooling episodes, defining the bases of a s-Atlantic region, some of these cooling episodes are associated with appearance intervals of the dinocyst species Svalbardella clausii, and Svalbardella cooksoniae. Here we present newly generated dinocyst, calcareous nannofossil, XRF and TEX86 proxy records across the upper Eocene to upper Oligocene from DSDP Site 112, southern Labrador Sea (latitude 54°N; Cores 13 to 5). The studied cores penetrate a deep-sea pelagic succession representing an interval of ~40 to 26.5 Ma. Our study reveals major depositional changes in the region of Site 112 across the EOT, including a decrease in the relative abundance of oceanic dinocysts (Impagidinium spp.), a decrease in carbonate content, higher siliciclastic delivery and grain coarsening. Furthermore, in the early Chattian we observe a high abundance of the potentially cold-water dinocyst S. clausii (up to 16% of the total dinocyst assemblage), possibly related to the Oi-2b cooling event. The preliminary results of micro-Fourier transform infrared (FTIR) spectroscopy (a method for identifying macromolecular cell compositions in algal cells, and thus nutritional ecologies) in three morphologically similar Eocene and Oligocene dinocyst taxa (S. clausii, S. cooksoniae and Palaeocystodinium golzowense) suggest that they had similar feeding strategies. However, subtle differences in the resulting FTIR spectra indicate some geochemical distinctions between them. The affinity of S. clausii to colder surface waters is tested by comparison of its distribution to the TEX86-derived sea surface temperature record.
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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 | 0.002 |
| 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) | 0.001 | 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".