Silurian extension in the Upper Connecticut Valley, United States and the origin of middle Paleozoic basins in the Québec embayment
Why this work is in the frame
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Bibliographic record
Abstract
Pre-Silurian strata of the Bronson Hill arch (BHA) in the Upper Connecticut Valley, NH-VT are host to the latest Ludlow Comerford Intrusive Suite consisting, east to west, of a mafic dike swarm with sheeted dikes, and an intrusive complex. The rocks are mostly mafic but with compositions ranging from gabbro to leucocratic tonalite. The suite is truncated on the west by the Monroe fault, a late Acadian thrust that carries rocks of the BHA westward over Silurian-Devonian strata of the Connecticut Valley-Gaspé trough (CVGT). Dikes intrude folded strata with a pre-intrusion metamorphic fabric (Taconian?) but they experienced Acadian deformation. Twenty fractions of zircon and baddeleyite from three sample sites of gabbro-diorite spanning nearly 40 km yield a weighted ^207^Pb/^206^Pb age of 419 ± 1 Ma. Greenschist-facies dikes, sampled over a strike distance of 35 km, were tholeiitic basalts formed by partial melting of asthenospheric mantle, with little or no influence from mantle or crustal lithosphere. The dike chemistry is similar to mid-ocean ridge, within-plate, and back-arc basin basalts. Parent magmas originated in the asthenosphere and were erupted through severely thinned lithosphere adjacent to the CVGT. Extensive middle Paleozoic basins in the internides of the Appalachian orogen are restricted to the Québec embayment of the Laurentian rifted margin, and include the CVGT and the Central Maine trough (CMT), separated from the BHA by a Silurian tectonic hinge. The NE-trending Comerford intrusions parallel the CVGT, CMT, and the tectonic hinge, and indicate NW-SE extension. During post-Taconian convergence, the irregular margins of composite Laurentia and Avalon permitted continued collision in Newfoundland (St. Lawrence promontory) and coeval extension in the Québec embayment. Extension may be related to hinge retreat of the northwest directed Brunswick subduction complex and rise of the asthenosphere following slab break-off. An alternative hypothesis is that the basins originated as pull-apart basins between northwest-trending, left-stepping, sinistral strike-slip faults along the southern flanks of the New York and St. Lawrence promontories.
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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 | 0.005 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.003 |
| 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 it