Contrasting Seismic Velocity and Compaction of Marine Calcareous Oozes and Volcaniclastic Deposits on the South Aegean Volcanic Arc
Bibliographic record
Abstract
Abstract International Ocean Discovery Program Expedition 398 recovered more than 2,200 m of volcaniclastic deposits from 12 sites and 28 holes from Santorini Caldera, Greece, and the surrounding rift basins in the South Aegean Volcanic Arc. We compare and contrast discrete shipboard measurements of physical properties (density, P‐wave velocity) of these volcaniclastic sediments with other uncemented marine sediments in the cores. The grain density (mass of solids divided by their volume, including any isolated vesicles) of volcaniclastic deposits is typically lower than that of volcanic glass and crystals and is sometimes less than 2 g/, indicating the preservation of isolated gas‐filled vesicles in erupted materials. Volcaniclastic deposits typically have higher P‐wave velocities but lower bulk densities than oozes and other marine sediments. In volcaniclastic deposits, lapilli have higher P‐wave velocities and lower bulk density than ash, the opposite trend of most sediment in which higher density is correlated with higher seismic velocity. We use granular physics models to show that the higher volcaniclastic P‐wave velocity originates from two effects: (a) lower pore volume outside clasts that increases elastic moduli and (b) isolated gas vesicles in volcanic clasts that lower bulk density. In volcaniclastic sediments there is relatively little change in physical properties to depths of several hundred meters below the seafloor, which we attribute to rough grain surfaces and lower intergranular (external) porosities that hinder compaction and the decrease of intergranular pore space. These trends lead to distinctive signatures of volcaniclastic sediments in reflection seismic images.
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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 | 0.001 | 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 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".