Acadian transpression and the exhumation of the sillimanite-bearing Passagassawakeag terrane along the Liberty-Orrington Fault, coastal Maine
Bibliographic record
Abstract
New detailed mapping in central coastal Maine shows the existence of a dextral strike-slip myIonitic shear zone, 250-500m thick, separating the sillimanite-grade Passagassawakeag terrane and the chlorite-grade Bucksport Formation of the Fredericton Trough. Foliation within the shear zone is near-vertical, with near-horizontal stretching lineations and pervasive dextral sense-of-shear indicators. Followed eastward, this northeast-striking terrane boundary turns north. A thin unit of alternating layers of quartz and gamet + biotite + magnetite, previously interpreted as the stratigraphic Rider Bluff unit, lies along this north-south striking (eastern) part of the Passagassawakeag-Bucksport boundary. Petrographic analysis demonstrates that the layering in this unit is a tectonic fabric, and the entire unit is interpreted as consisting of mytonites formed along a transpressional thrust, now overturned, along which the Passagassawakeag terrane was exhumed. If this is the case, the Liberty-Orrington shear zone may represent part of an orogen-scale dextral shear zone, continuous with the Penobscot Bay and Norumbega fault zones, through the Acadian orogeny.
 
 RÉSUMÉ
 De nouveaux travaux de cartographie déaillés du centre du littoral du Maine révèlént l'existence d'une zone cisaillée mylonitique à décrochement dextre de 250 à 500 metres d'épaisseur séparant le terrane à sillimanite de Passagassawakeag et la Formation à chlorite de Bucksport de la dépression de Fredericton. La zone cisaillée présente une schistosité presque verticale avec des lineations quasi-horizontales qui s'etirent ct des indicaieurs d'une orientation dextre pénétrante du cisaillement. Vers l’est, la limite de ce terrane orienté vers Ie nord-est toume vers le nord. Une unité mince de strates altemantes de quartz et de grenai + biotite + magnetite, auparavant interprétée comme l’uniteé stratigraphique de Rider Bluff, longe cette partie (orientale) à orientation nord-sud de la ligne de démarcation entrc Passagassawakeag et Bucksport. Une analyse pétrogrmphique révèle que la stratification à I'tntérieur de cette unité est de fabrique tectontque; on interprète I'ensemble de I'unité comme une unité constituée de mylonites s'étani formée Ie long d'un chevauchement transprcssionnel. maintenant renversé, le long duqucl Ic terrane de Passagassawakeag a été exhumé. Si c'est bien le cas la zone de cisaillement de Liberty-Orrington pourrait représenter une partic d'une zone de cisaillement dextre orogénique maintenant une continuité avec les zones faillées de la baie de Penobscot et de Norumbega pendant I'orogenese acadienne.
 
 Traduit par la rédaction
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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) | 0.008 | 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".