The widespread occurrence of coupled carbonate dissolution/reprecipitation in surface sediments on the Bahamas Bank
Bibliographic record
Abstract
Using two complimentary approaches (pore water advection/diffusion/ reaction modeling and stable isotope mass balance calculations) we show that carbonate dissolution/reprecipitation occurs on early diagenetic time scales across a broad range of sediments on the Great Bahamas Bank. The input of oxygen into the sediments, which strongly controls sediment carbonate dissolution, has two major sources---belowground input by seagrasses (that is, seagrass O~2~ pumping), and permeability-driven advective pore water exchange. The relative importance of these O~2~ delivery mechanisms depends on both seagrass density, and on how bottom water flow interacts with the seagrass canopy and leads to this advective exchange. Dissolution appears to involve the preferential dissolution of high-Mg calcite, and the rates of dissolution increase linearly with increasing seagrass density. Isotopic evidence of dissolution/reprecipitation is consistent with the occurrence of Ostwald ripening as the mechanism of reprecipitation, in which smaller crystals dissolve and then reprecipitate as larger crystals, with little or no change in mineralogy. Estimates of the aerially-integrated dissolution flux on the Bahamas Bank suggest that carbonate dissolution is an important loss term in the budget of shallow water carbonate sediments, and that on-bank carbonate dissolution, rather than offshore transport, may represent an important sink for gross shallow water carbonate production. Dissolution in carbonate bank and bay sediments may also be a significant alkalinity source to the surface ocean, and should be considered in global alkalinity/carbonate budget. Finally, coupled dissolution/reprecipitation may have a major impact on the stable isotope composition of carbonate sediments that are ultimately preserved in the rock record. These processes may therefore need to be considered, for example, when using carbon isotope records to obtain information on the operation of the global carbon cycle during the Phanerozoic.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".