Paleomagnetism of ∼1.09 Ga Lake Shore Traps (Keweenaw Peninsula, Michigan): new results and implications
Bibliographic record
Abstract
We report paleomagnetic data from a new section of the ∼1.09 Ga Lake Shore Traps exposed on Silver Island (10 flows) and on the adjacent mainland (two flows) along the northwestern coastline of the Keweenaw Peninsula in Michigan. We also present new data from nine additional lava flows, sampled from the tip of the peninsula previously studied by Diehl and Haig in 1994. Samples from all these lava flows yield well-defined characteristic magnetization directions upon thermal demagnetization. After structural tilt correction, the directions from Silver Island (site-mean declination, D = 276.9°; site-mean inclination, I = 44.4°; 95% radius of confidence for site mean, α 95 = 2.6°; number of samples, N = 10) and mainland (D = 298.7°, I = 36.0°, α 95 = 10.1°, N = 2) flows are close to the directions from equivalent lava flows from the upper (D = 277.8°, I = 41.0°, α 95 = 2.3°, N = 17) and lower (D = 300.0°, I = 34.9°, α 95 = 2.3°, N = 10) sections of the middle Lake Shore Traps exposed at the eastern tip of the Peninsula, respectively. Testing the paleomagnetic directions for serial correlation shows that some of the sequential lava flows on Silver Island and from the middle Lake Shore Traps at the tip of the Peninsula record the same vector of the geomagnetic field. Combining these correlated directions yielded new mean directions for Silver Island (D = 277.2°, I = 44.1°, α 95 = 3.1°, N = 8), and the upper (D = 277.0°, I = 40.4°, α 95 = 3.7°, N = 10) and lower (D = 298.6°, I = 33.3°, α 95 = 4.3°, N = 5) middle Lake Shore Traps at the tip of the Peninsula. The statistical similarity of paleomagnetic directions obtained from these two locations with significantly different structural trends supports the conclusions of prior studies that the curvature of the Midcontinent Rift is primary. The new paleomagnetic pole for the Lake Shore Traps is located at 23.1°N, 186.4°E (95% confidence for the paleomagnetic pole, Α 95 = 4.0°; N = 31) and merits a nearly perfect six-point classification on the paleomagnetic reliability scale.
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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 | 0.000 | 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 | 0.001 |
| 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".