The origin and occurrence of subaqueous sedimentary cracks
Bibliographic record
Abstract
Abstract The rock record attests that sediments have cracked at or below the sediment–water interface in strictly subaqueous settings throughout Earth history. In recent decades, a number of hypotheses have been advanced to explain this phenomenon, but these are widely regarded as being mutually exclusive and there is little consensus about which model is correct. In this paper, we first review the geometries, lithologies and range of facies in which subaqueous sedimentary cracks occur in the geological record, with particular attention to cracks in carbonates. We then evaluate current models for subaqueous cracking, emphasizing that different models may be correct with respect to different sets of cracks, but that cracking is generally a two-step process involving sediment stabilization prior to disruption. We also present the results of some simple new experiments designed to test the dominant models of crack formation. These results demonstrate for the first time that microbial mats can produce thin, shallow cracks at the sediment–water interface. We conclude that the presence of cracks in marine, brackish and lacustrine rocks should not be used uncritically to infer fluctuations in salinity in the depositional environment. Supplementary material: A video showing a micro-CT scan of a hand-sample from the Monteville Formation, South Africa is available at https://doi.org/10.6084/m9.figshare.c.3580673
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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 | 0.002 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".