Last Interglacial sea level derived from U-series dated fossil corals of the Turks and Caicos Islands
Bibliographic record
Abstract
The timing, magnitude, and evolution of sea-level change during the Last Interglacial period (Marine Isotope Stage (MIS) 5e) are subjects of ongoing debate. Previous estimates of global mean sea level (GMSL) generally converged on values of 5 to 10 meters above present levels, with one or more oscillations of up to several meters. However, more recent studies suggest considerably lower GMSL that peaked below 5 meters. Ancient coral reefs play a pivotal role in providing reliable constraints on MIS 5e sea level because they are often well preserved in the fossil record and can yield precise ages through U-series dating. Here we present a new series of high-precision U-series ages combined with detailed stratigraphic analysis and accurateelevation measurements of emergent in-situ fossil corals from Turks and Caicos Islands. We sampled well-preserved MIS 5e corals outcropping along the coastlines of North Caicos, Middle Caicos, West Caicos, and Providenciales islands. We identified corals from several paleo-habitats, including platform edge reefs and both isolated corals and patch reefs from the paleo-lagoon. The dominant coral species include Orbicella annularis, Pseudodiploria, Acropora palmata, Acropora cervicornis, and Porites porites. Many fossil corals show evidence of post-depositional alteration of their primary geochemistry. Their utility is therefore limited by their preservation. To identify unaltered corals and maximize the likelihood of closed to near-closed system behavior of our samples, we apply rigorous threshold criteria that screen samples by their mineralogy, U concentration, δ234Uinitial, and amount of detrital component. We further correct the ages for diagenetic disturbance of the U-Th isotope ratios. These results allow us to provide new sea-level constraints during MIS-5e and to assess the amount of ice melt during this period of pronounced warming.
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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 | 0.002 | 0.002 |
| 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".