Tectonic influences on the morphometry of the Sudbury impact structure: Implications for terrestrial cratering and modeling
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Bibliographic record
Abstract
Abstract— Impact structures developed on active terrestrial planets (Earth and Venus) are susceptible to pre‐impact tectonic influences on their formation. This means that we cannot expect them to conform to ideal cratering models, which are commonly based on the response of a homogeneous target devoid of pre‐existing flaws. In the case of the 1.85 Ga Sudbury impact structure of Ontario, Canada, considerable influence has been exerted on modification stage processes by late Archean to early Proterozoic basement faults. Two trends are dominant: 1) the NNW‐striking Onaping Fault System, which is parallel to the 2.47 Ga Matachewan dyke swarm, and 2) the ENE‐striking Murray Fault System, which acted as a major Paleoproterozoic suture zone that contributed to the development of the Huronian sedimentary basin between 2.45–2.2 Ga. Sudbury has also been affected by syn‐ to post‐impact regional deformation and metamorphism: the 1.9–1.8 Ga Penokean orogeny, which involved NNW‐directed reverse faulting, uplift, and transpression at mainly greenschist facies grade, and the 1.16–0.99 Ga Grenville orogeny, which overprinted the SE sector of the impact structure to yield a polydeformed upper amphibolite facies terrain. The pre‐, syn‐, and post‐impact tectonics of the region have rendered the Sudbury structure a complicated feature. Careful reconstruction is required before its original morphometry can be established. This is likely to be true for many impact structures developed on active terrestrial planets. Based on extensive field work, combined with remote sensing and geophysical data, four ring systems have been identified at Sudbury. The inner three rings broadly correlate with pseudotachylyte (friction melt) ‐rich fault systems. The first ring has a diameter of ˜90 km and defines what is interpreted to be the remains of the central uplift. The second ring delimits the collapsed transient cavity diameter at ˜130 km and broadly corresponds to the original melt sheet diameter. The third ring has a diameter of ˜180 km. The fourth ring defines the suggested apparent crater diameter at ˜260 km. This approximates the final rim diameter, given that erosion in the North Range is <6 km and the ring faults are steeply dipping. Impact damage beyond Ring 4 may occur, but has not yet been identified in the field. One or more rings within the central uplift (Ring 1) may also exist. This form and concentric structure indicates that Sudbury is a peak ring or, more probably, a multi‐ring basin. These parameters provide the foundation for modeling the formation of this relatively large terrestrial impact structure.
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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 | 0.000 |
| 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)
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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 it