Detailed crustal thickness variations beneath the Illinois Basin area: Implications for crustal evolution of the midcontinent
Bibliographic record
Abstract
Abstract We present high‐resolution imaging results of crustal and upper mantle velocity discontinuities across the Illinois Basin area using both common conversion point stacking and plane wave migration methods applied to P wave receiver functions from the EarthScope Ozark, Illinois, Indiana, and Kentucky experiment. The images reveal unusually thick crust (up to 62 km) throughout the central and southeastern Illinois Basin area. A significant Moho gradient underlies the NW trending Ste. Genevieve Fault Zone, which delineates the boundary between the Illinois Basin and Ozark Dome. Relatively thinner crust (<45 km) underlies most of the Precambrian highlands surrounding the Illinois Basin and beneath the rift‐related structures of the Reelfoot Rift and the Rough Creek Graben. We consider four hypotheses to explain the presence of thick crust under the central and southeastern Illinois Basin. Crustal thickening may have been produced (1) prior to its accretion to North America around 1.55 Ga and is an inherited characteristic of this crustal province; (2) by underthrusting or shortening during Proterozoic convergent margin tectonics around 1.55–1.35 Ga; (3) by Late Precambrian magmatic underplating at the base of older crust, associated with the creation of the Eastern Granite‐Rhyolite Province around 1.3 Ga; and (4) through crustal “relamination” during an episode of Proterozoic flat‐slab subduction beneath the Illinois Basin, possibly associated with the Grenville Orogeny.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".