The formation of orthogonal joint systems and cuboidal blocks: New insights gained from flat-lying limestone beds in the region of Havre-Saint-Pierre (Quebec, Canada)
Bibliographic record
Abstract
Vertical orthogonal joints are a common feature in shallow crustal rocks. There are several competing theories for their formation despite the ubiquity. We examined the exceptional exposures of orthogonal joints in flat-lying Ordovician limestone beds from the Havre-Saint-Pierre Region in Quebec, Canada (north shore of Saint-Lawrence River) to test conceptual models of joint formation in a natural setting. In the region, the spacing of cross-joints is consistently larger than the spacing of systematic joints by a factor of 1.5 approximately. The joint-spacing-to-bed-thickness ratios (s/t) are much larger in these beds (s/t = 4.3 for systematic joints, and 6.4 for cross-joints) than those in higher strained strata along the south shore of the Saint-Lawrence River (s/t = 1), highlighting the effect of tectonic strain in decreasing fracture spacing and block size. The high values of s/t indicate that cross-joint formation was unlikely caused by a switch from compression to tension once a critical s/t ratio for systematic joints was reached (as hypothesized in previous studies). We proposed a new model for the formation of orthogonal joint systems where the principal stress axes locally switch during the formation of systematic fractures. The presence of ladder-shaped orthogonal joints suggests a state of effective stress with σ1∗»0 > σ2∗>σ3∗ and where σ2∗-σ3∗ is within the range of fracture strength variability at the time of fracture. This research provides a new mechanical model for the formation of orthogonal joint systems and cuboidal blocks.
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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 | 0.001 | 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 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".