Evidence from IODP Site U1537 in the Dove Basin, Scotia Sea for a warmer Antarctica during the early Pleistocene (2.4-2.1 Ma) 
Bibliographic record
Abstract
IODP Site U1537 is located in a contourite deposit in the Dove Basin of the southeastern Scotia Sea, in 3,713 meters of water. It consists of alternating diatom oozes and silty clays, with variable amounts of sand to gravel-sized clasts delivered as IRD. Shipboard track measurements, weight percent ice-rafted detritus (IRD), 40Ar/39Ar hornblende and biotite age (provenance), and split core XRF elemental measurements were collected and examined to study Antarctic ice-sheet dynamics between 1.75 and 3.35 Ma, the Plio-Pleistocene transition. The highest and most variable amounts of IRD (from 0 to >0.4 g/cm2/ky) are in the earliest part of the study before 3.24 Ma. Between 3.24 and 2.4 Ma, with the exception of one sample, IRD comprises < 0.2 g/cm2/ky of the sediment. Between 2.4 and 2.1 Ma, IRD form < 0.05 g/cm2/ky, and from 2.1 Ma to the end of the study, they return to values of < 0.1, g/cm2/ky. With the exception of the lowest IRD interval (2.4 and 2.1 Ma), 40Ar/39Ar ages of biotite and hornblende grains are sourced from both East and West Antarctica, with the majority being between about 400 and 600 Ma old, broadly corresponding to the Pan-African event, and the assemblage of Gondwana. The 300,000-year, diatom-rich, low IRD interval between 2.4 and 2.1 Ma is unique in that all of the grains, except one, came from West Antarctica. Other Antarctic sites such as IODP Site U1361 (Wilkes Land), and ODP Site 1011 (northwest tip of the Antarctic Peninsula), also have their lowest IRD values during this time interval. We propose that this was a warmer time interval and that icebergs from East Antarctica either melted before reaching the Dove Basin or there were no ice-terminating glaciers.
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".