Orbital and eustatic control of basin hydrology during the first stage of the Messinian Salinity Crisis
Bibliographic record
Abstract
Abstract Gypsum and marls from the 15 cycles of the Messinian Yesares Member in the Sorbas Basin, SE Spain, were analysed using a multi‐isotope approach to reconstruct palaeo‐hydrological conditions of the basin and the wider Mediterranean region during the deposition of the Primary Lower Gypsum (PLG) of the Messinian Salinity Crisis (MSC) (~5.97–5.60 Ma). By analysing structurally‐bound water in sedimentary gypsum (CaSO 4 ·2H 2 O), the past oxygen and hydrogen isotopic composition of waters during evaporite formation is determined. These measurements are combined with water salinity inferred from gypsum fluid inclusions and isotopic analysis of strontium ( 87 Sr/ 86 Sr), calcium (δ 44 / 40 Ca), sulphur (δ 34 S) and oxygen of sulphate () in the same samples, as well as isotopic analysis (δ 44 / 40 Ca, 87 Sr/ 86 Sr, δ 18 O carb , δ 13 C) of the interbedded carbonate marls. The PLG in the Sorbas Basin did not form solely from the evaporation of seawater but rather precipitated from a hybrid brine consisting of seawater and a significant input of freshwater. The seawater/freshwater ratio changed through time and was influenced by (1) tectonic uplift and basin restriction, (2) obliquity‐driven glacial–interglacial sea level changes and (3) precession‐driven freshwater influx. A progressive freshwater increase up‐section reflects tectonic restriction of the basin, supported by 87 Sr/ 86 Sr trends, which start at seawater values in Cycle 2 and deviate upward. Two minor reversals in 87 Sr/ 86 Sr at ~5.84 and ~5.72 Ma reflect the role of obliquity‐controlled sea level and eccentricity‐modulated precession. Maximum divergence of 87 Sr/ 86 Sr from the seawater curve, as well as precipitation of authigenic dolomite with high δ 18 O carb , represent a temporary regime change to a freshwater‐dominated system coincident with the strongest glacial stages (Marine Isotope Stage TG20) and an eccentricity minimum at ~5.75 Ma. A gradual tectonic restriction of the Atlantic connection, superimposed on orbitally controlled glacio‐eustatic (obliquity‐dominated) and freshwater input (precession‐dominated) changes, led to gypsum‐marl deposition in Mediterranean marginal basins during the early MSC.
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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 | 0.000 | 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 | 0.001 |
| 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 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".