Late Silurian-Early Devonian tectono-sedimentary history of the Gaspe Belt in the Gaspe Peninsula: from a transtensional Salinic basin to an Acadian foreland basin
Bibliographic record
Abstract
ABSTRACT The Gaspe Belt is the largest middle Paleozoic belt in the Canadian Appalachians. The most complete stratigraphic record of Upper Ordovician to Middle Devonian rocks of this belt occurs in the Gaspe Peninsula, in the northeastern part of the Quebec re-entrant. Rocks of the Gaspe Belt rest unconformably on Cambrian to Ordovician rocks of the Humber and Dunnage zones, and are unconformably overlain by Carboniferous rocks. The regional metamorphic grade of the Gaspe Belt rocks is very low, and some units are still in the oil window. The deformation history of the Gaspe Belt rocks comprises multi-stage deformation events represented by two phases. A Late Silurian to Early Devonian phase, the Salinic disturbance, manifested by an unconformity, NW-trending folding, synsedimentary faulting, and intra-plate volcanism. The late Early to Middle Devonian Acadian phase is recorded by NE-trending folding, cleavage development and both reverse and strike-slip faulting within a transpressive setting during the oblique continental collision between Laurentia and Avalon (a peri-Gondwanan terrane), which took place farther southeast. The tectonic setting during the Salinic disturbance is consistent with continuous plate convergence (without subduction) after the Taconian Orogeny and before the Acadian continental collision. The paleogeographic maps of the Gaspe Belt during Pridolian, Pragian and Emsian times reflect the tectonic activity south of the Gaspe Peninsula. The switch from sinistral to dextral relative motion between Laurentia and Avalon terranes on the St. Lawrence promontory (Newfoundland) created a transtensional rift in the Quebec re-entrant (Gaspe Peninsula). During the Pridolian, normal block-faulting occurred particularly along the NW-trending eastern margin of the basin where reefs developed on the footwall of the faults. Intra-plate volcanism also occurred from Wenlockian to Emsian along the crustal weakness developed parallel to the NW-trending eastern margin of the basin. Pragian paleogeography shows a deep shelf, carbonate-rich, distal foreland basin in the north, and a siliciclastic turbidite proximal foreland basin developed in front of, and adjacent to, a southern land area. This paleogeographic distribution is compatible with the development of a peripheral foreland basin in front of the Acadian orogenic wedge caused by loading of the Laurentian margin during the convergence of the Avalon terrane within the Quebec re-entrant. During the Emsian, the northern deep-shelf carbonates were replaced by littoral and continental sands and gravels reflecting the growing Acadian orogenic wedge to the south and its deep erosion. RESUME La ceinture de Gaspe est la plus etendue des ceintures de roches du Paleozoique moyen des Appalaches canadiennes. La sequence stratigraphique la plus complete des roches de l'Ordovicien superieur au Devonien moyen de cette ceinture se trouve en Gaspesie dans la partie nord-est du reentrant de Quebec. Les roches de la ceinture de Gaspe y reposent en discordance sur celles du Cambrien-Ordovicien des zones de Humber et de Dunnage; elles sont recouvertes en discordance par les roches du Carbonifere. Le metamorphisme des roches de la ceinture de Gaspe est tres bas et certaines unites sont encore dans la fenetre a l'huile. L'histoire de la deformation des roches de la ceinture de Gaspe comprend plusieurs evenements que l'on peut regrouper en deux phases. Une phase d'age Silurien tardif-Devonien precoce, la phase salinique, qui se manifeste par une discordance, des plis d'orientation NO, des failles syn-sedimentaires et un volcanisme intraplaque. La phase acadienne de la fin du Devonien precoce au Devonien moyen comprend des plis d'orientation NE, un clivage regional, et des failles inverses et de coulissage. Cette phase acadienne est associee a une collision continentale oblique entre End_Page 202------------------------ Laurentia et Avalon (un terrane peri-gondwaneen) qui a eu lieu plus au sud. Le cadre tectonique de la phase salinique est coherent avec une tectonique continue de plaques convergents (sans subduction) apres l'orogenie taconienne et avant l'orogenie acadienne. Les cartes paleogeographiques du bassin de la ceinture de Gaspe pendant le Pridolien, le Praguien et l'Emsien refletent l'activite tectonique au sud de la Gaspesie. Le changement du mouvement relatif de senestre a dextre entre Laurentia et le terrane d'Avalon sur le promontoire du Saint-Laurent (Terre-Neuve) a cree un rift en transtension dans le reentrant de Quebec (Gaspesie). Pendant le Pridolien, des failles normales d'orientation NO ont ete actives plus particulierement le long de la marge orientale du bassin ou des recifs se sont developpes sur les hauts structuraux et le mur des failles. L'orientation NO de la marge orientale du bassin a aussi ete une zone de faiblesse favorisant l'eruption du volcanisme du Wenlockien a l'Emsien. La paleogeographie du Praguien montre, au nord, un bassin d'avant-pays distal, constitue de carbonates de plate-forme profonde et, au sud, un bassin d'avant-pays proximal constitue de roches silicoclastiques de facies a boues et turbidites adjacent a une zone emergee. Cet agencement est compatible avec la creation d'un bassin d'avant-pays peripherique au front du biseau orogenique acadien du a la surcharge sur la marge de Laurentia pendant la convergence du terrane d'Avalon dans le reentrant de Quebec. Pendant l'Emsien, le bassin d'avant-pays distal de plate-forme profonde s'est transforme en bassin littoral et continental a sables et graviers refletant la croissance du biseau orogenique et son erosion plus profonde. Traduit par l'auteur.
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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 | 0.001 | 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.051 | 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".