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Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Kamouraska Formation is a quartz-arenitic unit of latest Cambrian - earliest Ordovician age in the Quebec Appalachians that was deposited by hyperconcentrated to concentrated density flows in a meandering submarine canyon on the continental slope bordering the Iapetus Ocean, as outlined in a companion paper. Detailed petrographic study of the quartz arenites of the Kamouraska Formation combined with scanning electron microscopy of grain surface textures suggests that the quartz sands are of eolian origin having been derived from an inland desert or, less likely, a barrier beach dune system. Transport of the mature quartz-arenitic sand onto the shelf and deposition into the deep sea was not accompanied by substantial mixing with material from other sources thus preserving the inherited eolian characteristics. A modern analogue for the eolian interpretation of the deep-sea quartz-arenite beds is as follows: thick, Late Pleistocene eolian sand beds on a modern abyssal plain in the East Atlantic referred to as eolian-sand turbidites that were deposited in the deep sea during glacial sea level lowstands when eolian sand transport to canyon heads was enabled by an exposed and shortened shelf. Similarly, an established sea level lowstand at the Cambro-Ordovician boundary would have facilitated the introduction of eolian sand of the Kamouraska Foundation into canyon heads on the upper slope from where turbidity currents and related density flows were triggered. Correlation of the Kamouraska Formation with the quartz arenites of the Cairnside Formation of Quebec (Keeseville Formation in northern New York State, Nepean Formation in southern Ontario) links the deep-sea deposits with remnants of an inland dune system. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present new Sm–Nd isotope data for sediments from a core located on the continental slope of the St. Pierre Bank of Canada’s east coast. The Nd analyses indicate that the sediments were derived from two principal sources: the North American Shield that yields an average early Proterozoic isotopic signature and a younger Proterozoic signature attributed to Appalachian crustal sources. The Appalachian-sourced sediments predominated during the last glacial maximum (LGM) and were associated with low sedimentation rates (<30 cm/ka), with the exception of a strong North American Shield signature present in a detrital carbonate layer that corresponds to Heinrich Layer 1 (H1). The dominance of the Appalachian signature decreased subsequent to H1. The Appalachian signatures closely follow the distribution of sediments interpreted as locally derived glacial tills, while the North American Shield signatures follow the distribution of hemipelagic mud that was likely deposited by the Labrador Current. The Nd data are consistent with the persistence of the Wisconsinan Ice Sheet coverage of Newfoundland and the Grand Banks after the LGM, although the coverage began to wane prior to 12.5 ka as evidenced by the increasing influence of the Labrador Current. However, an increase in the Appalachian isotope signature at the close of the Younger Dryas event likely indicates the final melting of the ice sheet covering the Grand Banks and the Avalon Peninsula, and the initiation of the Labrador Current’s modern circulation pathway. Nous présentons de nouvelles données isotopiques Sm–Nd pour les sédiments provenant d’une carotte prélevée sur la pente continentale du Banc de Saint-Pierre de la Côte Est du Canada. Les analyses de Nd indiquent que les sédiments proviennent surtout de deux sources : le Bouclier nord-américain, lequel fournit une signature isotopique moyenne du Protérozoïque précoce et une signature Protérozoïque plus jeune attribuée aux sources de la croûte appalachienne. Les sédiments provenant de la source appalachienne prédominaient lors du dernier maximum glaciaire et ils sont associés à des taux de sédimentation faibles (< 30 cm/ka), à l’exception d’une forte signature du Bouclier nord-américain présente dans une couche de carbonate détritique qui correspond à l’événement Heinrich 1 (H1). La dominance de la signature appalachienne décroît après le H1. Les signatures appalachiennes suivent de près la distribution des sédiments, lesquels proviendraient de tills glaciaires, alors que les signatures du Bouclier nord-américain suivent la distribution d’une boue hémipélagique qui a fort probablement été déposée par le courant du Labrador. Les données Nd concordent avec la persistance de la couverture de la calotte glaciaire wisconsinienne de Terre-Neuve et des Grands Bancs après le dernier maximum glaciaire, bien que la couverture ait commencé à diminuer il y a plus de 12,5 ka, tel que mis en évidence par l’influence croissante du courant du Labrador. Toutefois, une augmentation de la signature isotopique appalachienne vers la fin de l’événement du Dryas Récent indique probablement la fonte finale de la calotte glaciaire qui recouvrait les Grands Bancs et la presqu'île Avalon et le début du tracé moderne de circulation du courant du Labrador. [ABSTRACT FROM AUTHOR]

Eastern Hudson Bay is characterized by falling relative sea level as a result of post-glacial isostatic rebound, which makes the region a natural laboratory for rapid forced regression, where the evolution of deltaic systems and offshore sedimentation patterns can be studied. A multidisciplinary approach involving airphoto analysis, offshore geophysical surveys, sediment coring, and facies and diatom analyses was used in this study of the Nastapoka River delta. The delta has formed as a result of the fluvial erosion of emerged Quaternary sediments but is mainly subaqueous. Offshore, in the prodelta zone, the oldest deposits are glaciomarine, laid down when the ice front of the receding Laurentide ice sheet stood on the Nastapoka hills some 7700–6800 years BP. Lateral equivalents of this glaciomarine unit are presently exposed on land. The shallow-water platform of the delta shows a thin surficial unit of wave-worked sand that overlies fine-grained, deeper water deposits derived from erosion of clay soils in the river catchment a few centuries ago, probably during periods of intense thermokarst activity. As the isostatic uplift continues, the deltaic platform will gradually emerge and be incised by the river channel.En conséquence du relèvement isostatique postglaciaire, la côte est de la baie d'Hudson est affectée par un abaissement rapide du niveau marin relatif. Cette région représente un véritable laboratoire naturel, dans un contexte de régression forcée, où l'évolution des systèmes deltaïques et la structure sédimentaire en eau profonde peuvent être étudiées. Une approche multidisciplinaire caractérisée par l'analyse de photographies aériennes, l'interprétation de relevés de géophysique marine, l'échantillonnage de sédiments, et l'analyse de facies et de diatomées a été appliquée dans la présente recherche sur le delta de la rivière Nastapoka. Le delta subaquatique actuel s'est formé suite à l'érosion fluviale de sédiments quaternaires émergés. Au large du delta, les dépôts anciens sont glacio-marins et se sont déposés lors de l'immobilisation de l'inlandsis Laurentidien sur les collines Nastapoka, entre 7700 et 6800 B.P. L'équivalent latéral de cette unité glacio-marine est actuellement exposé sur le continent. La plate-forme deltaïque peu profonde est caractérisée par un mince placage de sable, redistribué par l'action des vagues. Au-dessous, on trouve un faciès de matériel fin d'eau plus profonde. Ces sédiments fins proviennent de l'érosion d'argiles marines dans le bassin de la rivière, probablement érodés lors d'intenses périodes d'activité thermokarstique. Le relèvement isostatique se poursuivant, il est à prévoir que la plate-forme deltaïque va émerger et qu'elle sera incisée par un chenal fluvial. [ABSTRACT FROM AUTHOR]