Intracrater Evaporite Deposits of the Lake St. Martin Impact Structure: Implications for Mars
Bibliographic record
Abstract
Introduction: The Lake St. Martin impact structure is the result of a hypervelocity meteorite impact during the Early Triassic into what is now the northwest Interlake region of Manitoba. It is circular in shape and ~40km in diameter and has an abundance of shocked carbonates and intracrater evaporite deposits dominated largely by gypsum (CaSO4·2H2O) that have been open pit mined throughout the last 100 years [1]. It is these gypsum-rich intracrater evaporites, the presence of endolithic microbial communities within the gypsum deposits, and the presence of intracrater gypsum deposits on Mars [2], which make the Lake St. Martin impact structure a relevant analogue site for understanding the origin of what appear to be similar deposits on Mars. Gypsum deposits on Mars have previously been detected from orbit in the northern circumpolar dunes, but evidence for intracrater evaporite deposits has recently been found. Hydrated sulfate minerals have been detected in the Columbus, Gale and Gusev craters [2,3,4]. Such intracrater evaporite deposits are important to the understanding of early Mars as they may be indicative of hydrothermal activity or paleolakes. Recent CRISM data from the ~119km diameter Columbus crater (29oS, 166oW) has indicated the presence of polyhydrated sulfates and a kaolin group phyllosilicate [2]. One of the polyhydrated sulfates detected was gypsum which occurs as a deposit ringing the lower crater walls. Interbedding of the gypsum and clays was also detected [2,5]. Similar gypsum deposits are what make the Lake St. Martin impact structure a unique intracrater evaporite deposit on earth (Figure 1).
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".