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Copyright of Canadian Journal of Civil Engineering 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 Civil Engineering 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 hydraulic conductivity of six compacted tills from northern Quebec with different grain-size distributions has been studied in saturated conditions in the laboratory. The results show that compaction conditions play an important role in hydraulic conductivity. When considering the hydraulic conductivities of specimens compacted at degrees of saturation greater than the optimum, there is a good correlation with the content of clay-size particles. This paper provides a good practical tool for evaluating preliminary hydraulic conductivity values of compacted tills from northern Quebec on the basis of their grain-size distribution and compaction conditions.Key words: till, hydraulic conductivity, grain-size distribution, compaction conditions.La conductivité hydraulique de six tills du nord québécois présentant des granulométries différentes a été étudiée en conditions saturées, en laboratoire. Les résultats montrent que les conditions de compactage jouent un rôle important dans la conductivité hydraulique qui en résulte. Lorsque l'on considère les conductivités hydrauliques mesurées sur des échantillons compactés à des degrés de saturation plus élevés que celui à l'optimum, on obtient une bonne corrélation avec le pourcentage de particules de dimensions argileuses. Cet article fournit donc un bon outil pratique pour une évaluation préliminaire de la conductivité hydraulique des tills du nord québécois sur la base de leur granulométrie et des conditions de compactage.Mots clés : till, conductivité hydraulique, granulométrie, conditions de compactage. [ABSTRACT FROM AUTHOR]

This paper concerns the petrogenesis of the 504 ± 3 Ma Mont Chagnon massif, the southern extension of the Orford ophiolite in the Quebec Appalachians. The evolution of this massif is summarized in three stages marked by different magmatic series. In the Late Cambrian, the onset of southeastern subduction of the Iapetus basin generated an immature oceanic island arc made up of light rare-earth-element-depleted tholeiites, now preserved in the massif as a portion of the intrusive crustal unit, the dyke complex, and part of the lower volcanic unit. A phase of arc splitting, and concomitant partial erosion of the crustal section, was shortly followed by the eruption of rhyolite genetically related to felsic and low-Ti dykes, and trondhjemite. The geochemistry of these magmas bear some similarities with boninitic series. We believe these liquids derived from the partial melting of the Iapetus amphibolitized oceanic crust, with that of its Laurentian-derived sediments and nearby peridotite, either found as a trapped sliver above the subducting slab or as the slab itself. The final stage, preserved in the massif as a part of the intrusive section, the upper volcanic rocks, and the late-stage dykes, represents the back-arc opening. An ocean-island component is involved in the back-arc related petrogenetic processes, producing magmas with compositions intermediate between arc tholeiites and enriched back-arc basin basalts. This is the first report that the Iapetus basin was locally closing as early as Late Cambrian in the southern Quebec area.Cet article traite de la pétrogenèse du massif du mont Chagnon, daté à 504 ± 3 Ma, qui est l'extension méridionale de l'ophiolite d'Orford dans les Appalaches du Québec. L'évolution de ce massif est résumée en trois étapes déterminées par des suites magmatiques différentes. Au Cambrien tardif, le début de la subduction vers le sud-est d'Iapetus a crée un arc insulaire océanique immature composé de tholéiites appauvries en terres rares légères, maintenant préservées dans le massif en tant qu'une portion de l'unité crustale intrusive, le complexe de dykes et une partie de l'unité volcanique inférieure. Une phase de division de l'arc, et l'érosion partielle concomitante de la section de la croûte, a été suivie de près par l'éruption de rhyolite, génétiquement reliée aux dykes felsiques et à ceux faibles en Ti, de même qu'à la trondhjémite. La géochimie de ces magmas comporte des similitudes avec les séries boninitiques. Nous croyons que ces liquides proviennent de la fusion partielle de la croûte amphibolitisée d'Iapetus, de ses sédiments dérivés du craton Laurentia et de la péridotite avoisinante, qui se trouvent soit coincés en tant qu'écaille au-dessus de la lithosphère en subduction ou soit en tant que lithosphère subductée elle-même. L'étape finale, préservée dans le massif en tant qu'une partie de la section intrusive, les roches volcaniques supérieures et les dykes tardifs, représente l'ouverture de l'arrière-arc. Une composante d'île océanique est impliquée dans les processus pétrogénétiques reliés à l'arrière-arc, produisant des magmas dont les compositions sont intermédiaires entre les tholéiites d'arc et les basaltes enrichis de bassins d'arrière-arc. Ceci est le premier rapport qu'Iapetus se refermait localement aussi tôt que le Cambrien tardif dans le sud du Québec.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The preconsolidation pressure and overconsolidation ratio profiles are the most important factors related to the mechanical behaviour of clay deposits. They are interpreted on the basis of a limited number of laboratory tests, but the near-continuous information provided by the piezocone can allow local data to be extrapolated to an entire site. Numerous methods have been proposed for relating piezocone data to preconsolidation pressure and the overconsolidation ratio, but their validity is still uncertain. In this paper, nine methods are compared on the basis of data collected on 31 sensitive clay sites in Quebec whose preconsolidation pressure profiles are well known. Each method is briefly presented and the most promising are identified. The simplest method, which directly relates preconsolidation pressure to net tip resistance, also appears to be the most effective.Key words: clay, preconsolidation pressure, overconsolidation ratio, piezocone, correlations.Les profils de pression de préconsolidation et du rapport de surconsolidation constituent les éléments les plus importants en ce qui concerne le comportement mécanique des dépôts argileux. Leur évaluation se fait par un nombre limité d'essais de laboratoire, mais les données fournies par le piézocône de manière presque continue peuvent permettre une extrapolation à l'ensemble du site de ces données locales. De nombreuses méthodes ont été proposées pour corréler les données du piézocône et la pression de préconsolidation ou le rapport de surconsolidation mais leur validité est encore incertaine. Dans le présent article, neuf méthodes sont examinées à partir de données provenant de 31 sites d'argile sensible de la province du Québec pour lesquels les profils de pression de préconsolidation sont bien connus. Chaque méthode est brièvement présentée et les méthodes les plus intéressantes sont identifiées. Il semble que la relation entre la pression de préconsolidation et la résistance en pointe nette, qui est la plus simple, est aussi la plus efficace.Mots clés : argile, pression de préconsolidation, rapport de surconsolidation, piézocône, corrélations. [ABSTRACT FROM AUTHOR]

This paper presents the results of an extensive field investigation of several instrumented road sections in the Province of Quebec, Canada. Falling-weight deflectometer tests, static load tests on embedded plates at different depths, large dynamic cone penetration (DCP) tests, and piezocone tests (CPTU) were performed to study the mechanical response of the pavement. A correlation between elastic deformation modulus inferred from the plate load tests and DCP penetration index was obtained for nine different sites. A correlation between the equivalent elastic modulus of uniform subgrade soils and piezocone tip resistance was also established using data from the falling-weight deflectometer. A procedure for calculating the deflection basin for any pavement system placed over a more complex subgrade stratigraphy was proposed using these correlations. The proposed procedure was validated on two sites and its performance was adequate, since the calculated deflection basins agreed well with the measured deflection basins.Key words: penetration test, piezocone, deflection, pavement, in situ.Cet article présente les résultats d'une étude élaborée sur le terrain de plusieurs sections de route instrumentées dans la Province de Québec, Canada. Des essais au déflectomètre à masse tombante, de chargement statique sur des plaques enfouies à différentes profondeurs, de pénétration dynamique d'un gros cône (DCP), et de piézocône (CPTU) ont été réalisés pour étudier la réponse mécanique de la chaussée. Une corrélation entre le module de déformation élastique déduit des essais de chargement de plaques et l'indice de pénétration DCP a été obtenue pour neuf sites différents. Une corrélation entre le module élastique équivalent des sols de fondations uniformes et la résistance en pointe du piézocône a aussi été établie au moyen des données du déflectomètre à masse tombante. En partant de ces corrélations, on a proposé une procédure pour calculer le bassin de déflexion pour n'importe quel système de chaussée reposant sur une stratigraphie d'infrastructure complexe. La procédure proposée a été validée sur deux sites et sa performance a été adéquate puisque les bassins de déflexion calculés concordaient bien avec les valeurs mesurées.Mots clés : essai de pénétration, piézocône, déflexion, chaussée, in situ.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

To analyze the effects of strain rate and viscoplastic strain on consolidation of natural clay, this paper presents a nonlinear viscoplastic model in which viscoplastic behaviour is modeled by a unique effective stress (σ'[sub v] ) – viscous strain (ℇ[sub v] ) – viscous strain rate (ℇ[sup ·] [sub v] ) relationship. The proposed model can consider the effects of strain rate and viscoplastic strain on consolidation, to take into account the difference in strain rate between laboratory and field conditions, and the combined processes of generation and dissipation of pore pressure during consolidation. This model can also predict the behaviour of clay during stepwise loading, constant rate of strain, and relaxation of effective stress. The predicted values using numerical analysis are compared with measured values in laboratory tests and in situ, under an embankment built on soft clay at Berthierville, Quebec. It is possible to estimate the consolidation behaviour of natural clay with reasonable accuracy using the proposed nonlinear viscoplastic model.Key words: consolidation, soft clay, strain rate, viscoplastic, relaxation.Dans le but d'analyser les effets de la vitesse de déformation et de la déformation viscoplastique sur la consolidation de l'argile naturelle, cet article présente un modèle viscoplastique non linéaire dans lequel le comportement est modélisé par une relation unique contrainte effective-déformation visqueuse-vitesse de déformation visqueuse σ'[sub v] – ℇ[sub v] – ℇ[sup ·] [sub v] . Le modèle proposé peut prendre en considération les effets de la vitesse de déformation et de la déformation viscoplastique sur la consolidation pour tenir compte de la différence dans les vitesses de déformation entre les conditions en laboratoire et sur le chantier, de même que les processus combinés de génération et de dissipation de la pression interstitielle durant la consolidation. Ce modèle peut aussi prédire le comportement de l'argile en incluant le chargement par étape, la vitesse de déformation constante, et la relaxation de la contrainte effective. Les valeurs prédites au moyen de l'analyse numérique sont comparées avec celles mesurées dans les essais en laboratoire et in situ sous un remblai construit sur de l'argile molle à Berthierville, Québec. Il est possible d'estimer le comportement en consolidation de l'argile naturelle avec une précision raisonnable au moyen du modèle viscoplastique non linéaire proposé. Mots clés : consolidation, argile molle, vitesse de déformation, viscoplastique, relaxation.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The seismic attenuation in concrete has seldom been studied, although it is an important parameter for survey design. In this paper, the seismic Q factor is estimated from data measured at the Carillon dam. Three methods were used for this study: amplitude decay yielding a value of 5.1 ± 1.6, spectral ratio giving a value of 8.3 ± 3.5, and a value of 7.5 ± 14.9 was obtained from the rise-time technique. These values are weak compared with what is generally observed in rocks, and slightly lower than values obtained on laboratory concrete samples. However, the average P wave velocity measured on the investigated area is 4081 ± 95 m·s[sup –1] , an indication of the good quality of the material. Consequently, this strong attenuation could be attributed on one hand to energy loss, and on the other hand to scattering caused by the intrinsic cement–aggregate composition of concrete. It is also possible that an inadequate sensor coupling had the effect of reducing the observed Q value. Key words: seismic attenuation, concrete dams, microseismic monitoring, coupling.Paramètre important pour la planification de levés sismiques, l'atténuation sismique a été peu étudiée dans les bétons. Dans cet article, le facteur de qualité sismique Q est évalué au barrage de Carillon selon les méthodes du rapport des amplitudes, du rapport des spectres d'amplitude et du temps de montée. Les mesures obtenues sont respectivement de 5,1 ± 1,6, de 8,3 ± 3,5 et de 7,5 ± 14,9. Ces valeurs sont faibles en regard de ce qui est généralement observé dans les roches, et légèrement plus faibles que des valeurs mesurées sur des bétons en laboratoire. Par ailleurs, le béton de la partie du barrage auscultée présente une vitesse d'onde P moyenne de 4081 ± 95 m·s[sup –1] , indiquant une bonne qualité du matériau. En conséquence, la forte atténuation pourrait être attribuable d'une part à la perte de l'énergie sismique sous forme de friction, et d'autre part à une atténuation de diffusion occasionnée par la composition ciment-granulat intrinsèque du béton. Il est également possible qu'un couplage inadéquat des capteurs ait pour effet de réduire la valeur observée de Q. Mots clés : atténuation sismique, barrages en béton, auscultation microsismique, couplage. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Reviews 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.)

Analyzes field test results obtained by means of the Cambridge self-boring pressuremeter (SBMP) in a sensitive Champlain clay in Louiseville, Quebec. Parameters obtained from the interpretation of SBMP; Details of the use of stress paths; Properties of the soil encountered at the site.

The Paleoproterozoic southeastern Churchill Province (SECP) is located in the northeastern Canadian Shield of Labrador and Quebec. The SECP formed through the oblique collisions of the Archean Nain and Superior cratons with a third intervening Archean block, the core zone. The belt has a tripartite structure, comprising the Torngat Orogen (TO) formed by Nain craton – core zone collision in the east, the core zone in the centre, and the New Quebec Orogen (NQO) formed by Superior craton – core zone collision in the west. The SECP thus records transpressional development on the flanks of the Superior and Nain cratons as they indented northwards to form the larger Trans-Hudson – Nagssugtoqidian orogenic belt to the north. Principal stages of tectonic development were (1) 2.2–2.1 Ga crustal rifting of Nain and Superior cratons; (2) ca. 1.9 Ga subduction under eastern Nain craton; (3) ca. 1.87–1.85 Ga collision of Nain craton and core zone to form the TO; (4) 1.845–1.820 Ga sinistral transpression in the TO, and subduction under the western core zone; and (5) 1.82–1.77 Ga collision of Superior craton and core zone to form the NQO, in association with dextral transpression. Crustal-scale cross sections of the SECP have been developed from reflection and refraction seismic data. The western part of the NQO is dominantly west-vergent and associated with an imbricate thick-skinned thrust stack that ramps from the base of the crust. The core zone is characterized by a 35–40 km thick crust and pervasive east-dipping fabrics related to westerly thrusting. The TO is a narrow, doubly vergent belt, associated with a 48 km thick crust that forms a crustal root with a Moho relief of 12 km. The root is interpreted to result from attempted subduction of the core zone under the Nain craton, possibly as a result of mid-crustal wedging by the Nain craton. The TO was the site of intense convergence that resulted in excision of juvenile crust, possibly including tectonic removal of the axial magmatic arc. As a result, the middle to lower levels of the SECP consist largely of refractory Archean lithosphere. This may account for the lack of widespread post-collisional plutonism in the SECP and the preservation of the TO root.Le sud-est de la Province de Churchill (SECP, Southeastern Churchill Province; Paléoprotérozoïque) est situé dans le nord-est du Bouclier canadien, au Labrador et au Québec. Le SECP a été formé par des collisions obliques entre les cratons archéens de Nain et du Supérieur et un troisième bloc archéen intermédiaire, la zone noyau. La ceinture a une structure tripartite, comprenant l'orogène Torngat (TO), formé par la collision entre la zone noyau et le craton de Nain, à l'est, la zone noyau au centre et l'orogène du Nouveau-Québec (NQO), formé par la collision entre la zone noyau et le craton du Supérieur, à l'ouest. Le SECP enregistre donc le développement de transpressions sur les flancs des cratons de Nain et du Supérieur alors que ces derniers se déplaçaient vers le nord pour former la grande ceinture orogénique trans-hudsonienne – nagssugtoqidienne au nord. Les principaux stages de développement tectonique ont été : (1) la dérive crustale des cratons de Nain et du Supérieur, 2,2–2,1 Ga; (2) la subduction sous le craton de Nain oriental, vers 1,9 Ga; (3) la collision entre le craton de Nain et la zone noyau pour former l'orogène Torngat, vers 1,87–1,85 Ga; (4) la transpression senestre dans TO, 1,845–1,82 Ga; la subduction sous la zone noyau occidentale; (5) la collision entre le craton du Supérieur et la zone noyau pour former l'orogène du Nouveau-Québec, associée à de la transpression dextre, 1,82–1,77 Ga. Des coupes à l'échelle crustale du SECP ont été produites à partir de données de sismique réflexion et réfraction. La partie ouest de l'orogène du Nouveau-Québec est déversée surtout vers l'ouest et associée à une épaisse structure imbriquée de chevauchement qui remonte à partir de la base de la croûte. La zone noyau est caractérisée par une croûte dont l'épaisseur est de 35–40 km et des textures pénétrantes à pendage vers l'est qui sont reliées à du chevauchement vers l'ouest. L'orogène Torngat est une ceinture étroite à double vergence, associée à une croûte épaisse de 48 km qui forme une racine crustale avec un relief du Moho de 12 km. On interprète la racine comme une tentative de subduction de la zone noyau sous le craton de Nain, possiblement à la suite d'un coincement mi-crustal par le craton de Nain. L'orogène Torngat a été le site d'une intense convergence qui a eu comme résultat d'exciser la croûte juvénile, possiblement avec le retrait tectonique de l'arc magmatique axial. Il en a résulté que les niveaux mi-inférieurs du SECP consistent surtout de lithosphère archéenne réfractaire. Cela pourrait expliquer le manque de plutonisme post-collisionnel étendu dans le SECP et la préservation de la racine de l'orogène Torngat.[Traduit par la Rédaction] [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.)

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 Geotechnical Journal 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.)

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.)

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.)

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.)

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.)

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.)

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.)

Copyright of Canadian Journal of Civil Engineering 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.)

Investigates the mechanism of erosion and the factors influencing erosion rates of clay banks of the Saint Lawrence River along the Montréal to Lac Saint Pierre n Quebec. Literature review; Details on the experiments; Results of the study; Conclusions.

Analyzes the cave infill and associated biotic remains as indicators of Holocene environment in Gatineau Park in Quebec, Canada. Information on the study site; Methodology; Details on the paleoenvironmental conditions of the infill; Conclusions.

An improved paleogeography of the Quebec reentrant has been achieved by examining the nature and distribution of major sediment buildups within this reentrant. The Quebec reentrant has one side produced by rift faults and one side by a major transform fault. The Oak Hill Group was deposited near a triple-rift zone. Clastic sediments of this group formed a large delta that was fed by a major river flowing in the rift valley of the Ottawa graben. The delta must have prograded on a gentle slope platform. No other thick deltaic deposits ark known towards the northeast. Instead, facies analyses favor the existence of a promontory near Québec. Still farther to the northeast, the Saguenay graben was not the product of a triple-rift junction. However, it served to funnel sediments to a deep-sea fan, and the adjacent platform was narrow with a steep slope. The lateral distribution of sediments from the Ordovician Taconic orogeny can be explained by this improved paleogeographic reconstruction. The configuration of the Quebec reentrant required the arc to move into the reentrant. The Taconian tectonic wedge progressively accreted the thick sediment buildups that were the Oak Hill delta and the Bas-du-Fleuve deep-sea fan. This allowed them to act as new barriers to orogenic sediment dispersal as the orogeny proceeded. [ABSTRACT FROM AUTHOR]

The estuary of the St. Lawrence River between Baie-Comeau and Sept-Îies is an area where 50 to 100 earthquakes are detected yearly. This study defines the major lineaments of the Precambrian basement and compares them with mapped faults where possible, and examines their possible correlation with the local earthquakes. Onshore, aerial photographs, remote sensing images, and field mapping are used to identify the geological structures of the Precambrian basement, while offshore, they are interpreted from potential field (magnetic, gravity) and a published synthesis of seismic reflection profiles. The Precambrian basement dips towards the southeast under the Appalachian nappes with normal faults with kilometre-scale throw and east-west or ENE-WSW strikes. Onshore, a system of normal brittle faults with a complex history of movements crosscuts both the Precambrian basement and the overlying Ordovician sedimentary cover. Most earthquakes occur beneath the St. Lawrence River at focal depths between about 7 and 25 km that place them well within the Precambrian Shield. In the Lower St. Lawrence Seismic Zone, the trend of the normal faults that changes from SW-NE to mostly cast west, and lateral density anomalies possibly enhance the local stress level. It is also suggested that local faults could be weak because of crustal fluids at depth, possibly under hydrostatic pressure, or to fault gouge, which leads to a lower coefficient of friction. It is possible that the region was intensely fractured by the emplacement of the Sept-lies layered igneous complex. [ABSTRACT FROM AUTHOR]

In the southern Quebec Appalachians, the early tectonic history of the Laurentian margin (Humber zone) comprises foreland-propagating, northwest-directed thrust faulting, nappe emplacement, and regional prograde metamorphism in response to the obduction of large ophiolitic nappes during the Taconian orogeny. In the internal Humber zone, this event is dated at 462 ± 3 Ma (late Middle Ordovician), which is interpreted to represent the timing of near-peak Taconian metamorphism. Superimposed hinterland-directed structures are accompanied by retrograde metamorphism and consist of back thrusts and normal faults, which respectively delimit the northwestern and southeastern limbs of the Sutton and Notre-Dame mountains anticlinoria, both salient structures of the internal Humber zone of southern Quebec. Geochronologic data on the timing of hinterland-directed deformation vary from 431 to 411 Ma. Two tectonic models are presented and discussed, which may account for the Silurian Early Devonian evolution of the Laurentian margin: (1) back thrusting and syn- to post-compressional crystal extension in response to the tectonic wedging of basement-cored duplexes inducing delamination of supracrustal rocks; (2) tectonic exhumation of the internal Humber zone by extensional collapse. Evidence for Silurian - Early Devonian extensional tectonism in the Humber zone provides the basement infrastructures necessary for the creation and the onset of sedimentation in the Gaspé Belt basins (e.g., Connecticut Valley - Gaspé synclinorium). Several structural, metamorphic features in the internal Humber zone of the northwestern New England Appalachians yield analogous characteristics with those of southern Quebec and may have shared a similar Silurian Early... [ABSTRACT FROM AUTHOR]

The Taconian Humber Zone stretches from western Newfoundland to southern Quebec. The Early Cambrian slope succession in Newfoundland is found in the Curling Group, whereas in Quebec, various units were deposited during that first time slice. Biostratigraphic data allow correlation of the Curling Group with the Labrador Group in Newfoundland and with the newly time-constrained slope succession in Quebec. The end of the rift drift transition is marked by a sea-level lowstand at the end of the Early Cambrian. The Middle Cambrian to latest Early Ordovician passive margin history recorded five cyclic sea-level fluctuations. Three of these cycles are recorded in the shallow-marine Middle to Late Cambrian platform (Port au Port Group) and slope sediments preserved in the Cow Head and Northern Head groups in Newfoundland. The biostratigraphic information assists correlation with Cambrian passive margin units in Quebec. Major sea-level lowstands are recognized along the continental margin in early-middle Late Cambrian (Steptoan) and in late Late Cambrian (Sunwaptan). Even if the Quebec succession can be tied with its Newfoundland correlative, some significant differences in the nature of Upper Cambrian slope conglomerates argue for a tectonic control on the depth of erosion of the Cambrian continental margin. The Lower Ordovician record of the passive margin consists of two depositional cycles (Tremadocian-Arenigian) separated by a sea-level lowstand. This last event is well expressed in platform succession and is also recognized in conglomerate units found in the slope succession. [ABSTRACT FROM AUTHOR]

Detailed lithostratigraphic mapping of the Beekmantown Group of southwestern Quebec has refined the field application of the previously proposed tripartite division of the group (i.e., Theresa, Beauharnois, and Carillon formations). The group is a peritidal-dominated succession that accumulated on the epicontinental Laurentian passive margin. Biostratigraphic data based on conodonts from this group indicate an Early to early Middle Ordovician age and arc partially time-correlative with the Wallace Creek to Naylor Ledge strata of the Philipsburg Group, southern Quebec. This conodont biostratigraphy sheds new light on the temporal evolution and depositional framework of the Beekmantown platform. The platform evolved as a distally steepened ramp during deposition of the Theresa Formation and the Ogdensburg Member of the Beauharnois Formation (early to middle Ibexian). Correlative strata of the Philipsburg Group include the Wallace Creek and Morgan Corner formations, which represent outer platform sediments. The coarse-grained sandstone of the Theresa Formation accumulated in the innermost platform, whereas coarse-grained carbonates of the Ogdensburg Member indicate open-marine, subtidal to intertidal carbonate sand shoals. By late Ibexian, the platform developed a pronounced margin where thrombolites flourished under high-energy conditions. These arc represented by the thrombolite-rich Hasting Creek and Naylor Ledge formations of the Philipsburg Group. Consequently, a broad lagoon formed on the lee side of the platform margin, where low-energy conditions prevailed and accumulation of burrow-mottled dolostones of the Huntingdon Member of the upper Beauharnois Formation took... [ABSTRACT FROM AUTHOR]

The Charlevoix area, which is host to an impact structure of Devonian age, straddles the boundaries among crystalline rocks of the Grenville Province, the Cambrian-Ordovician sedimentary succession of the St. Lawrence Platform, and accreted units of the Appalachian orogen. The area features well-developed supracrustal fault systems attributed to impact cratering. A major fault system oriented from northeast to northwest consists of normal faults marked by cataclastic and gouge breccias and, less frequently, by pseudotachylyte. Detailed mapping of faults both within and outside the Charlevoix impact crater suggests that brittle faulting occurred both before and after impact cratering. Polymictic fault breccias occurring along some supracrustal faults are the clearest evidence of impact-related fault rocks in the Charlevoix area. The St-Laurent fault, trending to the northeast, represents a major structure interpreted as being related to Late Proterozoic - early Paleozoic rifting of the lapetus Ocean. However, the St-Laurent fault crosses the Charlevoix impact crater without major deflection, suggesting post-impact reactivation. The fault systems in the Charlevoix area are interpreted to be pre-impact structures related to the opening of the Iapetus Ocean, most of which have also been reactivated during the Devonian cratering event and in post-impact time, the latter most likely coeval with the Atlantic Ocean rifting in Mesozoic time. [ABSTRACT FROM AUTHOR]

Presents a study of spatial and temporal variation of distributed water quality in municipal drinking water utilities in Quebec. Key parameters responsible for the differences between the groups of utilities; Capacity of studied utilities to handle the acute disease risk associated with microorganisms; Parameters upon which it may be possible to act to achieve better water quality in each of the utility groups; Comparisons of the characteristics of water quality at the source; Chlorination conditions in the plant; Water quality from the entrance to the extremity of the distribution system.

Presents a study that investigated the implications of a stillstand of the Quebec-Labrador ice margin in the Tyrell Sea at 8 ka BP in the Nastapoka drift belt. Methodology; Significance of the Nastapoka drift belt; Conclusion.

Discriminant analysis of 80 samples from the Western Carbonate Platform Facies and the Eastern Transitional Carbonate–Siliciclastic Platform Facies of the Gun River Formation (Lower Silurian) on Anticosti Island, Quebec, indicates the degree to which different conodont communities were related to particular lithofacies. The statistical analysis reveals that during most of the Gun River Formation deposition, the conodont distributional pattern of the Western Carbonate Platform Facies and the Eastern Transitional Carbonate–Siliciclastic Platform Facies of the formation remained stable, and that the boundary of the two facies oscillated eastward and westward. The analysis indicates quantitatively that Icriodella deflecta had a nearshore environmental preference, whereas Rexroadus kentuckyensis tended to reside in offshore environments. These two species play the most important role in differentiating conodont communities and determining the relationship between conodont communities and lithofacies among all of the 22 species known from the Gun River Formation.Une analyse discriminante de 80 échantillons du faciès occidental de la plate-forme carbonatée et du faciès oriental de la plate-forme de transition carbonate–siliclastique de la Formation de Gun River (Silurien inférieur) sur l'île d'Anticosti, au Québec, indique le degré de relation entre les diverses communautés de conodontes et des lithofaciès particuliers. L'analyse statistique révèle que, lors de la déposition de la plus grande part de la Formation de Gun River, le patron de distribution des conodontes du faciès occidental de la plate-forme carbonatée et celui du faciès oriental de la plate-forme de transition carbonate–siliclastique de la formation sont demeurés stables et que la limite entre les deux faciès oscillait vers l'est et vers l'ouest. Les résultats quantitatifs de l'analyse indiquent que Icriodella deflecta préférait les environnements littoraux alors que Rexroadus kentuckyensis avait plus tendance à rester dans des environnements au large. Ces deux espèces sont les plus significatives pour différencier les communautés de conodontes et déterminer la relation entre les communautés de conodontes et les lithofaciès parmi toutes les 22 espèces connues dans la Formation de Gun River.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The Lac-Saint-Jean anorthosite suite (LSJAS) is the largest ensemble of plutons in the Grenville Province. Zircons from a pluton in the central part of the LSJAS yield an age of 1140[sup +10] [sub –5] Ma, which accords with existing 1157–1142 Ma ages determined from the southern part of the LSJAS. The Du Bras granite is a linear pluton emplaced into the dominantly dextral Pipmuacan shear zone (PSZ). The U–Pb zircon age of 1148 ± 2 Ma for the Du Bras granite confirms earlier proposals that it is a granophyre, formed at greater depths by partial melting of paragneiss by the heat of the crystallizing anorthosite. Parts of the pluton are strongly deformed by the shear zone, and other parts cut the shear zone. This suggests that the pluton dates one phase of movement of the PSZ. The Canton-St-Onge wollastonite deposit was developed in paragneisses preserved within the PSZ. Titanite from this deposit gives an age of 1163 ± 18 Ma, identical within error to that of the Du Bras granite, indicating that this pluton may have provided the skarn fluids. A second plutonic cycle comprises the post-tectonic Astra granite, which stitches the PSZ, and an amazonite-bearing pegmatite dyke. Zircons gave an age of 1028 ± 2 Ma for the Astra granite. The amazonite-bearing dyke only yielded monazite, one fraction of which gave an age similar to that of the Astra granite. Other fractions record the effects of a thermal event at 1020–1017 Ma that may be related to a widespread magmatic event. The undeformed Venus de Milot syenitic intrusion yields a U–Pb age of 988 ± 2 Ma. It was emplaced along the northwest-trending Lac Rioux fault, indicating that one phase of movement occurred before 988 Ma. Another strand of the same fault system also cuts the intrusion, showing later reactivation that may have been associated with the formation of the Saguenay Graben.La suite anorthositique du lac Saint-Jean (LSJAS) est le plus gros ensemble de plutons de la Province de Grenville. Des zircons provenant d'un pluton dans la partie centrale de la suite a donné un âge de 1140[sup +10] [sub –5] Ma, ce qui concorde avec des âges existants de 1157–1142 Ma déterminés dans la partie sud de la suite anorthositique. Le granite de Du Bras est un pluton de forme linéaire mis en place dans la zone de cisaillement, surtout dextre, de Pipmuacan (PSZ). Un âge U–Pb de 1148 ± 2 Ma, sur zircon, pour le granite de Du Bras confirme les propositions antérieures qu'il s'agit d'un granophyre, formé à grande profondeur d'une fusion partielle du paragneiss par la chaleur de la cristallisation de l'anorthosite. Certaines parties du pluton sont assez fortement déformées par la zone de cisaillement alors que d'autres parties recoupent la zone de cisaillement. Cela suggère que le pluton peut servir à dater une phase de mouvement de la PSZ. Le gisement de wollastonite du canton Saint-Onge s'est développé dans des paragneiss préservés à l'intérieur de la PSZ. De la titanite provenant de ce gisement donne un âge de 1163 ± 18 Ma, identique, à l'intérieur de la marge d'erreur, à celui du granite de Du Bras, indiquant que ce pluton peut avoir fourni les fluides du skarn. Un second cycle plutonique comprend le granite post-tectonique Astra, qui suture la PSZ, et un dyke de pegmatite à amazonite. Les zircons ont donné un âge de 1028 ± 2 Ma pour le granite Astra. Le dyke à amazonite n'a donné que de la monazite, dont une portion a donné un âge semblable à celui du granite Astra. D'autres portions enregistrent les effets d'un événement thermal vers 1020–1017 Ma, lequel peut être relié à un événement magmatique de grande envergure. La syénite non déformée de Vénus de Milot a donné un âge U–Pb de 988 ± 2 Ma. Elle a été mise en place le long de la faille à tendance N–O du lac Rioux, indiquant qu'une phase de mouvement a eu lieu avant 988 Ma. Une autre branche de ce même système de failles recoupe aussi l'intrusion, montrant une réactivation tardive qui pourrait avoir été associée à la formation du graben du Saguenay.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Mesoproterozoic lamprophyre dikes occur at four localities within the ~1010 Ma Labrieville anorthosite in the Grenville Province of southern Quebec. All dikes are thin (<20 cm wide), oriented ~N57W, and steeply dipping. Three are biotite lamprophyres, but the fourth is dominated by amphibole. Laser total-fusion [sup 40] Ar/[sup 39] Ar analyses on amphibole or biotite yield minimum ages for the dikes of 945.5 ± 8 Ma, 907.0 ± 5.9 Ma, 892.0 ± 6.2 Ma, and 889.2 ± 9.8 Ma. A crystallization age of ~1 Ga for all dikes is consistent with these data and Rb–Sr isotopic systematics. All lamprophyres contain high levels of Cr (284–393 ppm), Ni (101–180 ppm), Ba (1380–5580 ppm), Sr (2359–3109 ppm), and rare-earth elements (REE; La[sub N] = 191–288), with average La[sub N] /Lu[sub N] = 26 and no Eu-anomalies. At 1 Ga, all lamprophyres have a similar initial Sr isotopic ratio of ~0.7034, similar to Bulk Earth. In contrast, ℇ[sub Nd ] values vary considerably from –4 to –10.2, indicating sources with variable long-term light-REE enrichment. Negative correlations between [sup 143] Nd/[sup 144] Nd and La/Nb and K suggest involvement of at least two source components, probably asthenosphere and metasomatized subcontinental lithosphere. The lamprophyres are only slightly younger than ~1010 Ma Labrieville massif, which is also alkalic and enriched in Sr and Ba relative to most other anorthosites. The lamprophyres provide unequivocal evidence for a Sr- and Ba-rich component in the lithospheric mantle that may have contributed to the parental magmas of Labrieville and other andesine anorthosites in this part of Quebec.Des dykes de lamprophyre datant du Mésoprotérozoïque se retrouvent à quatre endroits à l'intérieur de l'anorthosite de Labrieville, ~1010 Ma, dans la Province de Grenville au sud du Québec. Tous les dykes sont minces (largeur < 20 cm), ils sont orientés ~N57W et ils ont un pendage abrupt. Trois sont composés de lamprophyres à biotite, mais le quatrième est dominé par de l'amphibole. Des analyses de fusion totale [sup 40] Ar/[sup 39] Ar au laser sur l'amphibole ou la biotite ont donné des âges minimums pour les dykes de 945,5 ± 8 Ma, 907,0 ± 5,9 Ma, 892,0 ± 6,2 Ma et 889,2 ± 9,8 Ma. Un âge de cristallisation de ~1 Ga pour tous les dykes concorde avec ces données et les données isotopiques systématiques Rb–Sr. Tous les lamprophyres contiennent des niveaux élevés de Cr (284–393 ppm), de Ni (101–180 ppm), de Ba (1380–5580 ppm), de Sr (2359–3109 ppm) et d'éléments des terres rares (La[sub N] = 191–288) avec une moyenne La[sub N] /Lu[sub N] = 26 et aucune anomalie Eu. À 1 Ga, tous les lamprophyres ont un rapport isotopique initial Sr semblable de ~0,7034, comparable à l'ensemble de la Terre. Par contre, les valeurs ℇ[sub Nd] varient considérablement de –4 à –10,2, indiquant des sources dont l'enrichissement en éléments de terres rares légers varie à long terme. Des corrélations négatives entre [sup 143] Nd/[sup 144] Nd et La/Nb et K suggèrent l'implication de composantes d'au moins deux sources, probablement l'asthénosphère et la lithosphère sous-continentale métasomatisée. Les lamprophyres sont seulement un peu plus jeunes que le massif de Labrieville, ~1010 Ma, lequel est également alcalin et enrichi de Sr et de Ba par rapport à la plupart des autres anorthosites. Les lamprophyres fournissent des évidences sans équivoque pour une composante riche en Sr et Ba dans le manteau lithosphérique, laquelle aurait pu contribuer aux magmas parents de Labrieville à d'autres anorthosites à andésine de cette région du Québec.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

We used gravity and magnetic data to extend geological features across Ungava Bay and Hudson Strait, from northern Quebec and Labrador to Baffin Island. Tectonic domains identified on land were extended offshore by visual inspection of the potential fields. The boundaries identified on colour shaded relief maps were drawn on the original marine magnetic profiles to verify the robustness of the conclusions. Our interpretation in Ungava Bay remains speculative but gives some insight into the architecture of the northeastern Canadian Shield. Onshore, where trends are well marked, the magnetic fabric of the Superior Province reappears east of the New Quebec Orogen in the western core zone. Geochronology and geochemical data also suggest the affinity of the western core zone with the Superior Province. On the gravity map, the New Quebec Orogen appears to vanish offshore. A major trend in magnetic and gravity gradients can be followed offshore possibly as far north as Hudson Strait. It has been identified as the extension of the George River and Moonbase shear zones. The De Pas Batholith is associated with a linear trend west of this shear zone. To the east, several features appear distinctly in the magnetic map. A narrow northwest-trending anomaly can be followed from Quebec all the way to Baffin Island. On land, this feature marks the western limit of the Lake Harbour Group. Two wide north-trending bands that can be followed from the Torngat Orogen all the way to Baffin Island are interpreted as the extensions of the Lac Lomier Complex and Tasiuyak Domain.Nous avons utilisé des données gravimétriques et magnétiques pour prolonger les caractéristiques géologiques à travers la baie d'Ungava et le détroit d'Hudson du nord du Québec et du Labrador jusqu'à l'île de Baffin. Les domaines tectoniques identifiés sur terre ont été prolongés au large par une inspection visuelle des champs de potentiels. Les limites indiquées sur des cartes topographiques en couleurs ont été tracées sur les profils magnétiques marins originaux afin de vérifier la solidité des conclusions. Dans la baie d'Ungava, notre interprétation demeure spéculative, mais elle donne un aperçu de l'architecture du nord-est du Bouclier canadien. Sur terre, où les tendances sont bien marquées, la texture magnétique de la Province du Supérieur réapparaît à l'est de l'orogène du Nouveau-Québec dans la zone noyau occidentale. La géochronologie et les données géochimiques suggèrent aussi une affinité entre la zone noyau occidentale et la Province du Supérieur. Sur la carte gravimétrique, l'orogène du Nouveau-Québec semble disparaître vers le large. Une tendance majeure dans les gradients magnétiques et gravimétriques peut être suivie au large, possiblement aussi loin que le détroit d'Hudson. Cette tendance a été identifiée comme la prolongation des zones de cisaillement de la rivière George et de Moonbase. Le batholite de dePas est associé à une tendance linéaire à l'ouest de cette zone de cisaillement. Vers l'est, plusieurs caractéristiques sont distinctes sur la carte magnétique. Une étroite anomalie à tendance nord-ouest peut être suivie de Québec jusqu'à la terre de Baffin. Sur terre, cette caractéristique marque la limite ouest du Groupe de Lake Harbour. Deux larges bandes à tendance nord, qui peuvent être suivies de l'orogène Torngat jusqu'à l'île de Baffin, sont interprétées comme étant des extensions du complexe du lac Lomier et du domaine de Tasiuyak.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT) of the Lithoprobe program included 1200 km of normal-incidence seismic profiles and seven wide-angle seismic profiles across Archean and Proterozoic rocks of Labrador, northern Quebec, and the surrounding marine areas. Archean crust is 33–44 km thick. P-wave velocity increases downwards from 6.0 to 6.9 km/s. There is moderate crustal reflectivity, but the reflection Moho is unclear. Archean crust that stabilized in the Proterozoic is similar except for greater reflectivity and a well-defined Moho. Proterozoic crust has similar or greater thickness, variable lower crustal velocities, and strong crustal reflectivity. Geodynamic processes of Paleoproterozoic growth of the Canadian Shield are similar to those observed in modern collisional orogens. The suturing of the Archean Core Zone and Superior provinces involved whole-crustal shearing (top to west) in the Core Zone, linked to thin-skinned deformation in the New Quebec Orogen. The Torngat Orogen sutures the Nain Province to the Core Zone and reveals a crustal root, in which Moho descends to 55 km. It formed by transpression and survived because of the lack of postorogenic heating. Accretion of the Makkovik Province to the Nain Province involves delamination at the Moho and distributed strain in the juvenile arcs. Delamination within the lower crust characterizes the accretion of Labradorian crust in the southeastern Grenville Province. Thinning of the crust northwards across the Grenville Front is accentuated by Mesozoic extension that reactivates Proterozoic shear zones. The intrusion of the Mesoproterozoic Nain Plutonic Suite is attributed to a mantle plume ponding at the base of the crust.Le transect du programme Lithoprobe des zones continentales et extracôtières de la partie est du Bouclier canadien (ECSOOT) comprend 1200 km de profils sismiques à incidence normale et sept profils sismiques à grand-angle à travers les roches archéennes et protérozoïques du Labrador, du nord du Québec et des régions marines avoisinantes. La croûte archéenne a une épaisseur de 33 à 44 km. La vitesse de l'onde P augmente vers le bas de 6,0 km s[sup -1] à 6,9 km s[sup -1] . La réflectivité crustale est modérée, mais la réflexion du Moho n'est pas claire. La croûte archéenne qui s'est stabilisée au Protérozoïque est semblable, à l'exception d'une plus grande réflectivité et une discontinuité Moho bien définie. La croûte protérozoïque présente une épaisseur similaire ou plus grande, des vitesses variables pour la croûte inférieure et une forte réflectivité de la croûte. Les processus géodynamiques de croissance du Bouclier canadien au Paléoprotérozoïque sont semblables à ceux observés dans des orogènes de collision modernes. La suture de la zone noyau archéenne et de la Province du Supérieur implique du cisaillement de la croûte entière (du haut vers l'ouest) dans la zone noyau, relié à de la déformation en couches minces dans l'orogène du Nouveau-Québec. L'orogène Torngat suture la Province de Nain à la zone noyau et révèle une racine crustale dans laquelle le Moho descend à 55 km. Cet orogène s'est formé par transpression et a survécu en raison du manque d'élévation de température post-orogénique. L'accrétion de la Province de Makkovik à la Province de Nain implique une délamination au Moho et une distribution des contraintes dans les arcs juvéniles. La délamination à l'intérieur de la croûte inférieure caractérise l'accrétion de la croûte labradorienne dans le sud-est de la Province de Grenville. Un amincissement de la croûte vers le nord à travers le front du Grenville est accentué par une extension, au Mésoprotérozoïque, qui a réactivé les zones de cisaillement protérozoïques. L'intrusion de la Suite plutonique de Nain (Mésoprotérozoïque) est attribuée à un panache du manteau stagnant à la base de la croûte.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Within the Trans-Hudson Orogen in northern Quebec and southern Baffin Island, parautochthonous Archean basement and Paleoproterozoic cover, as well as allochthonous (accreted) Paleoproterozoic units, are exposed in a series of antiformal culminations and complementary synclinoria. The parautochthonous rocks of the Superior Province margin and two assemblages of accreted Paleoproterozoic units (Ungava and Meta Incognita crustal terranes) define a basic tripartite crustal architecture which is characterized by polyphase deformation and metamorphic histories. Early structures and mineral assemblages are recognized in all three crustal components and shown to be temporally distinct. The earlier structures and assemblages are overprinted by younger elements and mineral assemblages that are related to at least three regional contraction episodes and one thermal event that are common to all crustal components of the orogen. Close correlation of regional aeromagnetic data in northern Quebec and southern Baffin Island with the three crustal components offers a first-order approximation of the distribution of basement lithological units across Hudson Strait. Continuation of the aeromagnetic domains beneath Ungava Bay to northeastern Quebec and northern Labrador allows for the southward extrapolation of the tripartite Trans-Hudson Orogen crustal architecture into the Lithoprobe Eastern Canadian Shield Onshore–Offshore Transect area.À l'intérieur de l'orogène trans-hudsonien au nord du Québec et au sud de l'île de Baffin, le socle parautochtone archéen et le couvert paléoprotérozoïque, de même que les unités paléoprotérozoïques allochtones (accrétées) affleurent dans une série de culminations antiformes et de synclinoriums complémentaires. Les roches parautochtones de la bordure de la Province du Supérieur et deux assemblages d'unités accrétées paléoprotérozoïques (les terranes crustaux Ungava et Meta Incognita) définissent une architecture crustale tripartite qui est caractérisée par de la déformation polyphasée et des historiques métamorphiques. Des structures précoces et des assemblages de minéraux sont reconnus dans les trois composantes crustales et on démontre qu'elles sont distinctes dans le temps. Les structures et les assemblages les plus précoces sont surimprimés par des éléments plus jeunes et des assemblages de minéraux qui sont reliés à au moins trois épisodes régionaux de contraction et un événement thermique qui sont communs à toutes les composantes crustales de l'orogène. Une bonne corrélation entre les données aéromagnétiques du nord du Québec et du sud de l'île de Baffin et les trois composantes crustales donne une approximation de premier ordre de la distribution des unités lithologiques du socle à travers le détroit d'Hudson. La continuation des domaines aéromagnétiques sous la baie d'Ungava jusqu'au nord-est du Québec et au nord du Labrador permet d'extrapoler l'architecture crustal tripartite de l'orogène trans-hudsonien vers le sud, à l'intérieur de la région du transect Lithoprobe des zones continentales et extracôtières de la partie est du Bouclier canadien (ECSOOT).[Traduit par la Rédaction] [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]

The highly condensed Lower to Middle Ordovician deep-water succession from the Cap-des-Rosiers Group at Matane bears three conspicuous graptolite faunas of late Tremadoc to mid-Darriwilian age. The Tremadoc fauna belongs to the Aorograptus victoriae Zone. In the Castlemainian Isograptus victoriae maximodivergens Zone fauna the earliest Pseudisograptus species, Pseudisograptus initialis n. sp., appears together with the ancestral Arienigraptus gracilis. A Darriwilian fauna with Holmograptus spinosus and Bergstroemograptus crawfordi represents the youngest pre-Nemagraptus gracilis Zone fauna described from the Quebec Appalachians.La séquence d'eau profonde hautement concentrée du Groupe de Cap-des-Rosiers à Matane (Ordovicien inférieur à moyen) comporte trois faunes proéminentes de graptolites datant du Trémadocien tardif au Darriwilien moyen. La faune du Trémadocien appartient à la zone Aorograptus victoriae. Dans la faune de la zone Isograptus victoriae maximodivergens (Castlemainien), l'espèce la plus précoce de Pseudisograptus, le Pseudisograptus initialis n. sp., apparaît ensemble avec l'espèce ancestrale Arienigraptus grascilis. Une faune du Darriwilien, comportant Holmograptus spinosus et Bergstroemograptus crawfordi, représente la faune de la zone pré-Nemagraptus gracilis la plus jeune décrite en provenance des Appalaches du Québec.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

A 500 m-thick lens of carbonatitic ultrabasic lapilli tuffs and lavas interbedded with platformal Povungnituk sediments in the foreland of the Cape Smith Belt is its earliest known magmatism and may relate to its initial rifting. The sequence comprises tuffs capped in part by effusives. Accretionary and cored lapilli in the tuffs and pillows in the lavas suggest emplacement in a shallow marine environment. Its current assemblage of antigorite, chlorite, talc, and (in part primary?) carbonate, magnetite, ilmenite, minor chromite, and phlogopite results from probable concurrent hydrothermal alteration and subsequent greenschist regional metamorphism. Surviving accessory minerals: apatite, monazite, zircon, rutile, and aeschenite(?) are widespread but scarce. Carbonate (mostly dolomite) is a major and integral component of the rock and interpreted as an original, albeit recrystallized, magmatic constituent. Magnetite is conspicuous in the tuffs: as lapilli and lapilli cores, locally as giant crystals, and as stringers. Except in subhedral groundmass crystals, its negligible TiO[sub 2] is evidence of its hydrothermal reconstitution. Compositions of chromite cores and rare relicts of phlogopite crystals are consistent with mantle derivation. Rock compositions are low in SiO[sub 2] (<35%) and Al[sub 2] O[sub 3] (<3%), high in MgO (>25 wt.%) and alkaline. The immobile incompatible elements (e.g., Zr, average 260 ppm; Nb, average 130 ppm) and the light rare-earth elements are enriched. The rocks are compositionally similar to type Siberian meimechites and closely resemble the "meimechite"–carbonatite eruptives of Castignon Lake, Labrador Trough. Based on experimental evidence, Lac Leclair magmas are interpreted as originating by minor partial melting of carbonated mantle at ~100 km depths and reaching the surface via conduits opened by deep rifting that initiated the Cape Smith segment of the Trans-Hudson Orogen.Une lentille de 500 m d'épaisseur de tufs volcaniques à lapilli, carbonatitiques et ultrabasiques, interstratifiés avec des sédiments de plate-forme de Povungnituk dans l'avant-pays de la ceinture de Cape Smith en représente le magnétisme connu le plus précoce et pourrait être reliée à sa dérive initiale. La séquence comprend des tufs recouverts partiellement par des roches extrusives. Dans les tufs et les coussins des laves, des lapilli accrétionnés et à noyau suggèrent une mise en place dans un environnement marin peu profond. L'assemblage présent d'antigorite, de chlorite, de talc, ainsi que de carbonate, de magnétite, d'ilménite, de chromite mineure et de phlogopite (en partie primaires ?) résulte d'une probable altération hydrothermale concurrente et d'un subséquent métamorphisme régional au faciès des schistes verts, Les minéraux accessoires restants : l'apatite, la monazite, le zircon, le rutile et l'aeschénite(?) sont répandus mais rares. Le carbonate (surtout de la dolomite) forme une partie intégrante et majeure de la roche et il est considéré comme un constituant magmatique original, quoique recristallisé. La magnétite est évidente dans les tufs : en tant que lapilli et de noyaux de lapilli, par endroits sous forme de cristaux géants et de veinules. Sauf pour les cristaux hypidiomorphes de la pâte, la présence négligeable de TiO[sub 2] est une preuve de reconstitution hydrothermale. Les compositions des noyaux de chromite et de rares reliques de cristaux de phlogopite concordent avec une provenance du manteau. Les roches contiennent peu de SiO[sub 2] (<35 %) et de Al[sub 2] O[sub 3] (<3 %), beaucoup de MgO (>25% poids) et elles sont alcalines. On y retrouve un enrichissement des éléments incompatibles immobiles (par ex. Zr, moy. 260 ppm; Nb, moy. 130 ppm) et des éléments de terres rares légers. Les roches ont une composition semblable aux méiméchites de la Sibérie et ressemblent beaucoup aux roches effusives « méiméchite »–carbonatite de la région du lac Castignon dans la Fosse du Labrador. En se basant sur des preuves expérimentales, les magmas du lac Leclair proviendraient de la fusion partielle de manteau carbonaté à des profondeurs d'environ 100 km et ils auraient atteint la surface en suivant des conduits ouverts par la dérive intensive qui a initié le segment Cape Smith de l'orogène trans-hudsonien[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]