Deformation in carbonates and its contribution to fold & thrust belt architecture
Bibliographic record
Abstract
Fold and thrust belts are frequent structures that form under a compressive regime. They record a variety of deformation that guides earthquake ruptures and controls seismic hazard. The Naukluft mountains of Namibia with their extraordinary exposure, present a unique opportunity to study carbonate fault rocks. Through linked field investigations and microstructural analysis, we aim to map how changes in fault strength contributed to larger scale architectural evolution of a fold and thrust belt. Mineralogical assemblage of the stacked nappes show units of carbonate and shale in the lower to upper greenschist facies, correlating to the seismological depth for carbonate rocks. Cross cutting relations prove that the Naukluft Nappe Complex (NNC), previously thought to form through gravity sliding, is a foreword-propagating fold and thrust belt, stacking Neo Proterozoic sedimentary nappes on top of each other, and on top of the cambrian Nama fore-rift group. Most thrusts separating the stacked nappes are made of 20-150 meters of calc mylonites, except for the youngest two brittle thrust faults, including the basal thrust. Brittle deformation is recorded by localized brecciation and the development of discrete faults. The brittle faults follow the same orientation as the overall transport direction of the nappe complex. Ductile shearing is facilitated by crystal plastic deformation, leading to grain size reduction, and grain boundary sliding. Both ductile mylonite units and the younger brittle faults are also overprinted by later brittle faults, and between the ductile and brittle behavior, we map a unit of a block-in-matrix. We found no clear correlation between the temporal evolution of the nappe complex and the thickness of ductile shear zones. We show evidence for embrittlement through exhumation of a carbonate terrane, and suggest that it may be important to consider the effects of deeper ductile behavior in “Coulomb wedge” descriptions of thin-skinned thrust belts.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".