Origin of Sr-Rich Magnesian Calcite Mud in a Holocene Pond Basin (Lee Stocking Island, Bahamas)
Bibliographic record
Abstract
Abstract Magnesian calcite represents about 90% of carbonate mud that has accumulated in a Holocene (< 1.5 ka) pond basin on Lee Stocking Island, Bahamas. Additional minerals include aragonite (< 10%), as well as trace amounts of dolomite, celestine, and silt- to sand-size reworked authigenic gypsum. The mud fraction constitutes 40-75 % of the sediment, and has a bimodal grain size. More than 80% of the particles are < 2 μm in size, made up of mostly stubby, elongate euhedral to ragged, anhedral crystals, as well as spheroidal and platy calcite bodies, 0.15-0.2 μm in diameter. Silt-size particles are mostly 20-40 μm in diameter, and consist of fragmented bioclasts (mostly mollusks) as well as angular to subrounded clasts of microporous magnesian calcite (2-4 wt % Mg). Intraparticle porosity arises from likely microborings (≪ 1 μm), whereas larger circular pores, 1-2 μm, could be sites of once-present bacterial filaments around which calcite precipitated. The mud fraction of the pond sediment is variably Sr-rich: in the clay size fraction, bulk Sr concentrations are 4000-7000 ppm; microprobe analysis of microporous silt-size particles reveals Sr contents of up to 1.2 wt %. δ18OPDB (-1 to -3‰) and δ 13CPDB (-3 to -6‰) values of clay-size sediment are distinct from surrounding Quaternary sediment and limestone, and suggest that the clay fraction is not mechanically weathered detritus. I interpret the mud-size particles to have precipitated from warm (> 30°C) hypersaline pond waters, at times exceeding gypsum saturation. Elevated Sr content is likely a product of changing Sr/Cafluid ratios in pond water related to gypsum formation. By incorporating carbon and oxygen isotope stratigraphies of indigenous biota (the foraminifer Ammonia beccarii, and gastropod Cerithidea sp.) with that of pond mud, this sedimentary basin preserves a record of high-order environmental changes over the last 1500 years that likely influenced mud precipitation and its accumulation; these changes reflect variation in water residence time, temperature, likely bacterial productivity, and bicarbonate sources.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 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 teacher head, 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".