Chloride and chlorine isotopes (<sup>36</sup>Cl and δ<sup>37</sup>Cl) as tracers of solute migration in a thick, clay‐rich aquitard system
Bibliographic record
Abstract
Detailed vertical profiles of dissolved Cl − and its isotopes ( 36 Cl and δ 37 Cl) provided new information on the origin and systematics of this conservative tracer in pore waters of a thick aquitard system. The aquitard system consists of surficial Quaternary clay‐rich till (80 m thick) deposited 30–20 kyr B.P., overlying Cretaceous marine clay (76 m thick) deposited ∼71 Ma. The distribution of Cl − , δ 37 Cl, and Br − showed the presence of five distinct end‐members for Cl − : the top of the unoxidized till, a regional aquifer underlying the Cretaceous clay, two localized geological heterogeneities (sand streaks) in the till, and glacial meltwater emplaced with the till and still present at depths of between 36 and 60 m. Numerical simulations of the transport of Cl − from the sand streaks indicated that this geochemical profile has been developing throughout most of the Holocene. The 36 Cl measurements showed that the age of the dissolved Cl − in the upper Cretaceous clay is likely between 0.75 and 1.9 Myr. The 36 Cl measurements further suggested that the dissolved Cl − in the till was not directly derived from the underlying Cretaceous clay. Finally, it was not possible to quantify the effects of isotopic fractionation of 37 Cl relative to 35 Cl because of diffusion in this aquitard system.
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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".