The Grand Manan Terrane of New Brunswick: Tectonostratigraphy and Relationship to the Gondwanan Margin of the Iapetus Ocean
Bibliographic record
Abstract
Recently gathered stratigraphic and U–Pb geochronological data indicate that the pre-Triassic rocks of the Grand Manan Terrane on the eastern side of Grand Manan Island can be divided into: (1) Middle Neoproterozoic (late Cryogenian) quartzose and carbonate sedimentary sequences (The Thoroughfare and Kent Island formations); (2) a Late Neoproterozoic (early Ediacaran) volcanic-arc sequence (Ingalls Head Formation); and (3) Late Neoproterozioc (mid- Ediacaran) to earliest Cambrian (early Terreneuvian) sedimentary and volcanic-arc sequences (Great Duck Island, Flagg Cove, Ross Island, North Head, Priest Cove, and Long Pond Bay formations). A comparison to Precambrian terranes on the New Brunswick mainland (Brookville and New River terranes) and in adjacent Maine (Islesboro Terrane) suggests that the sedimentary and volcanic sequences of the Grand Manan Terrane were deposited on the continental margin of a Precambrian ocean basin that opened during the breakup of Rodinia in the Middle Neoproterozoic (Cryogenian) and closed by the Early Cambrian (Terreneuvian) with the final assembling of Gondwana. Rifting associated with the initial opening of the Paleozoic Iapetus Ocean began in the Late Neoproterozoic (late Ediacaran) and so overlapped in time with the closing of the Precambrian Gondwanan ocean. The southeastern margin of the Iapetus Ocean is defined by thick sequences of quartz-rich Cambrian sediments (within the St. Croix and Miramichi terranes of New Brunswick) that were largely derived from recycling of Precambrian passive-margin sedimentary rocks preserved in the Grand Manan and Brookville terranes of New Brunswick and in the Islesboro Terrane of Maine. These Precambrian terranes are interpreted to represent dextrally displaced basement remnants of the Gondwanan continental margin of Iapetus, consistent with the model of a two-sided Appalachian system proposed by Hank Williams in 1964 based on his work in Newfoundland.SOMMAIREDes données stratigraphiques et géochronologiques U–Pb obtenues récemment indiquent que les roches prétriasiques du terrane de Grand Manan du côté est de l’île Grand Manan peuvent être répartis en: 1) séquences sédimentaires quartzeuses et carbonatées du Néoprotérozoïque moyen (Cryogénien tardif) (formations de Thoroughfare et de Kent Island); 2) séquence d’arc volcanique du Néoprotérozoïque tardif (Édiacarien précoce) (formation d’Ingalls Head); 3) séquences sédimentaires et d’arc volcanique du Néoprotérozoïque tardif (milieu de l’Édiacarien) au tout début du Cambrien (Terreneuvien précoce) (formations de Great Duck Island, Flagg Cove, Ross Island, North Head, Priest Cove et Long Pond Bay). Une comparaison avec des terranes du Précambrien dans la partie continentale du Nouveau-Brunswick (terranes de Brookville et New River) et dans le Maine adjacent (terrane d’Islesboro) semble indiquer que les séquences sédimentaires et volcaniques du terrane de Grand Manan se sont déposées sur la marge continentale d’un bassin océanique précambrien qui s’est ouvert durant la fracturation de la Rodinia au Néoprotérozoïque moyen (Cryogénien) et s’est fermé au Cambrien précoce (Terreneuvien) avec l’assemblage final du Gondwana. La distension continentale associée à l’ouverture initiale de l’océan Iapetus au Paléozoïque a commencé au Néoprotérozoïque tardif (Édiacarien tardif) et a donc partiellement coïncidé avec la fermeture de l’océan précambrien du Gondwana. La marge sud-est de l’océan Iapetus est définie par d’épaisses séquences de sédiments cambriens riches en quartz (dans les terranes de St. Croix et de Miramichi du Nouveau-Brunswick) issus en grande partie du recyclage de roches sédimentaires de la marge continentale passive du Précambrien préservées dans les terranes de Grand Manan et de Brookville au Nouveau-Brunswick et dans le terrane d’Islesboro dans le Maine. Ces terranes précambriens sont interprétés comme la représentation de vestiges, ayant subi un déplacement dextre, du socle de la marge continentale gondwanienne de l’océan Iapetus, ce qui concorde avec le modèle d’un système appalachien à deux côtés proposé par Hank Williams en 1964 sur la base de ses travaux à Terre-Neuve.
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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 | 0.001 |
| 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) | 0.000 | 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".