Constraints on emplacement and timing of the Steen River impact structure, Alberta, Canada
Bibliographic record
Abstract
The Steen River impact structure (SRIS) is a buried, complex crater located in NW Alberta, Canada. It was discovered in the mid 1900’s and was initially thought to be an endogenic igneous intrusion. With the growth of impact studies on Earth and other planets, the SRIS was recognized as such in the 1960’s. Since then, numerous exploratory wells have been drilled in and around the structure to assess its economic potential. While many of these wells are proprietary, three cores collected in 2000 are available for research and have been the focus of the most recent SRIS studies. A ubiquitous product of impact events is impact breccia, which may contain clasts of target material and melt. At the well-studied Ries impact structure in Germany, this breccia is classified as suevite. The impact breccia observed at the SRIS is similar to the Ries suevite; however, the term “suevite” has been applied to many impact structures and its formation mechanism is still debated. In previous studies, three cores from the SRIS (ST001, ST002, and ST003) were logged by hand and characterized in detail using thin sections; however, a representative, yet detailed, mineralogical overview of the core was lacking. In this thesis, hyperspectral imaging was used to quickly scan the three cores and make detailed mineralogical maps of each. Results highlight hydrothermal and ammoniated minerals in the SRIS impact breccia, and aid in refining the emplacement model for the suevite-like breccia. The only published age of the crater is poorly constrained and conflicts with the stratigraphy overlying the crater. To better constrain the SRIS age, zircons were extracted from the core samples and characterized using secondary ion mass spectrometry. Zircons are commonly used for U-Pb geochronology because they can withstand most geological disturbances and may incorporate radiogenic isotopes into their crystal structure. By analyzing both granite- and melt-derived zircons, this study aimed to constrain the age of the SRIS impact event and compare it to the known age of the Proterozoic basement rocks.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.003 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".