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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.)

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.)

Four different seismic methods were used extensively to evaluate the shear wave velocity of soils and rock in the city of Ottawa, Canada, from which the travel-time weighted average shear wave velocity (Vs) from surface to 30 m in depth (Vs30) and the fundamental frequency (F0) were computed. Three main geological or geotechnical units were identified with distinct shear wave velocities: these consist of very loose thick post-glacial fine-grained sands, silts, and clays (Vs <150 m/s, thickness up to 110 m), firm glacial sediments (Vs ~580 m/s, thickness ~3 m), and very firm bedrock (Vs ~1750-3550 m/s). The seismic methods applied were downhole interval Vs measurements at 15 borehole sites, seismic refraction-reflection profile measurements for 686 sites, high-resolution shear wave reflection 'landstreamer' profiling for 25 km in total, and horizontal-to-vertical spectral ratio (HVSR) of ambient seismic noise to evaluate the fundamental frequency for ~400 sites. Most of these methods are able to distinguish the very high shear wave impedance of and depth to bedrock. Sparse earthquake recordings show that the soil amplification is large for weak motion when the soil behaves linearly. Quatre méthodes sismiques différentes ont été grandement utilisées afin d'évaluer la vitesse des ondes de cisaillement des sols et roches dans la ville d'Ottawa, Canada, à partir desquelles la vitesse moyenne des ondes de cisaillement pondérée selon le temps de parcours (Vs) de la surface jusqu'à une profondeur de 30 m (Vs30) et la fréquence fondamentale (F0) ont été calculées. Trois unités géologiques ou géotechniques principales ont été identifiées selon des vitesses des ondes de cisaillement distinctes : des sables, silts et argiles post-glaciaires fins, lâches et épais (Vs <150 m/s, jusqu'à 110 m d'épaisseur), des sédiments glaciaires fermes (Vs ~580 m/s, ~3 m d'épaisseur) et du substratum rocheux très ferme (Vs ~1750-3550 m/s). Les méthodes sismiques appliquées étaient des mesures de Vs par intervalle en fond de forage pour 15 sites de forage, des mesures du profil de réfraction-réflexion sismique pour 686 sites, du profilage de la réflexion des ondes de cisaillement à haute résolution « landstreamer » pour 25 km linéaire au total, et le ratio spectral horizontal-vertical (RSHV) du bruit sismique ambiant pour l'évaluation de la fréquence fondamentale sur environ 400 sites. La majorité de ces méthodes sont capables de distinguer l'impédance très élevée aux ondes de cisaillement et la profondeur jusqu'au substratum rocheux. Quelques mesures de séismes montrent que l'amplification du sol est grande pour des mouvements faibles lorsque le sol de comporte de façon linéaire. [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.)

This study presents Last Interglacial and Holocene vegetation and climate changes at Fog Lake (67°11′N, 63°15′W) on eastern Baffin Island, Arctic Canada. The vegetation cover is reported as vegetation structural types (or biomes). July air temperature and sunshine during the growing season (June–July–August–September) were reconstructed from pollen assemblages using the modern analogue technique. The vegetation of the Last Interglacial period evolved from a prostrate dwarf-shrub tundra to a low- and high-shrub tundra vegetation. The succession of four Arctic biomes was distinguished from the Last Interglacial sediments, whereas only one Arctic biome was recorded in the Holocene sediments. From ca. 8300 cal. years BP to present, hemiprostrate dwarf-shrub tundra occupied the soils around Fog Lake. During the Last Interglacial, growing season sunshine was higher than during the Holocene and July air temperature was 4 to 5 °C warmer than present. A principal component analysis helped in assessing relationship between floristic gradients and climate. The major vegetation changes through the Last Interglacial and Holocene were driven by July air temperature variations, whereas the minor, or subtle, vegetation changes seem rather correlated to September sunshine. This study demonstrates that growing season sunshine conditions can be reconstructed from Arctic pollen assemblages, thus providing information on feedbacks associated with cloud cover and summer temperatures, and therefore growing season length. Cette étude présente les changements climatiques et de végétation survenus au cours du dernier interglaciaire et de l’Holocène au lac Fog (67°11′N, 63°15′O), sur la côte est de la Terre de Baffin, dans l’Arctique canadien. La couverture végétale est décrite sous forme de biomes, c.-à-d. de structures de végétation. La température de l’air en juillet et l’ensoleillement lors de la saison de croissance (juin, juillet, août, septembre) ont été reconstitués à partir d’assemblages polliniques selon la méthode des analogues modernes. La végétation de la dernière période interglaciaire a évolué d’une toundra arbustive naine, prostrée à une toundra arbustive basse et haute. Une succession de quatre biomes est visible dans les sédiments du dernier interglaciaire, alors qu’un seul biome est observé dans les sédiments de l’Holocène. Une toundra arbustive hémiprostrée colonize les sols des environs du lac Fog depuis environ 8300 années. Au cours du dernier interglaciaire, l’ensoleillement durant de la saison de croissance était plus élevé que lors de l’Holocène et la température de juillet était de 4 à 5 °C plus chaude qu’actuellement. Une analyse en composantes principales a permis d’évaluer la relation entre les gradients floristiques et le climat. Les changements majeurs de végétation lors du dernier interglaciaire et de l’Holocène découlent principalement des variations de la température de juillet, alors que les changements de végétation plus subtils sont plutôt liés à l’ensoleillement en septembre. Cette étude démontre que les conditions d’ensoleillement lors de la saison de croissance peuvent être déduites à partir des assemblages polliniques des sédiments de l’Arctique, fournissant ainsi de l’information pertinente sur les rétroactions associées au couvert nuageux et aux températures estivales et donc sur la durée de la saison de croissance. [ABSTRACT FROM AUTHOR]

This study examines the physical and geochemical properties of near-surface sediments, as well as the geochemical and stable O–H–C isotope composition of (ground)surface waters in and around the Haughton impact structure region (Devon Island, Nunavut) to determine the types of weathering (mechanical, (bio)chemical) and their relative contribution in this polar desert environment. The surface sediments collected from the Allen Bay and Thumb Mountain formations surrounding the impact crater are dominated by sand-sized particles; whereas the impact melt breccias inside the crater have a greater abundance of silt-sized particles. The subsurface sediments in the Allen Bay formation show a near equal amount of sand- and silt-sized particles. However, the micromorphologies of the sand-sized particles collected at the surface revealed that these grains, irrespective of the local geology, were heavily fractured. By contrast, fractures and rounded pits are observed on the surface of the sand grains located within the active layer; whereas those located just above the permafrost table have only rounded cavities on their surface. The (ground)waters also show variations in their solute concentration with depth; the highest concentrations being found in the groundwaters near the top of permafrost. Taken together, these observations suggest that there is a progressive evolution from a mechanically dominated weathering regime near the surface, to increasing chemical weathering with depth. The transition from mechanical weathering near the surface to increasing chemical weathering with depth can be attributed to the decreasing frequency and intensity of mechanical weathering processes (i.e., frost action, wetting–drying, thermal dilation) with depth, and to the presence of permafrost, which allows a greater availability of water for chemical aqueous reactions at the base of the active layer. Cette étude examine les propriétés physiques et géochimiques de sédiments près de la surface ainsi que la composition géochimique et la composition des isotopes stables O–H–C des eaux souterraines et de surface dans la région de la structure d’impact Haughton et autour de celle-ci (île Devon, Nunavut) afin de déterminer le type de météorisation (mécanique, (bio)chimique) et leur contribution relative dans cet environnement de désert polaire. Les sédiments de surface recueillis des formations d’Allen Bay et de Thumb Mountain entourant le cratère d’impact comprennent surtout des particules de la taille du sable, alors que les brèches de fusion d’impact à l’intérieur du cratère présentent plus de particules de la taille du silt. Les sédiments sous la surface dans la Formation d’Allen Bay montrent des quantités presque égales de particules de la taille du sable et du silt. Toutefois, la micromorphologie des particules de la taille du sable recueillies à la surface révèle que ces grains étaient grandement fracturés, peu importe la géologie locale. Cependant, des fractures et de petites dépressions arrondies sont observées à la surface des grains de sable situés dans la couche active, alors que les particules situées tout juste au-dessus de la nappe du pergélisol ne présentent que des cavités arrondies à leur surface. Les eaux souterraines présentent aussi des variations de concentration de soluté avec la profondeur; les plus hautes concentrations se retrouvent dans les eaux de surface près du sommet du pergélisol. Prises ensemble, ces observations suggèrent qu’il existe une évolution progressive d’un régime d’altération principalement mécanique près de la surface à une altération de plus en plus chimique avec la profondeur. La transition d’une altération mécanique à proximité de la surface à une altération chimique plus poussée avec la profondeur peut être attribuée à la fréquence et l’intensité décroissantes des processus d’altération mécanique (c.-à-d. l’action du gel, les cycles de mouillage et séchage, la dilatation thermique) avec la profondeur et à la présence du pergélisol qui permet une plus grande disponibilité d’eau pour des réactions chimiques aqueuses à la base de la couche active. [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 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 Journal of Environmental Engineering & Science 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.)

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]

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]

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]

Near Woodbridge, northwest of Toronto, Ontario, a 15 metre-high railroad cut and associated borrow pit, first excavated in 1962, exposed a multiple till sequence and intervening fossiliferous sediments. Work over the next 35 years revealed that Illinoian York Till, early Wisconsinan Sunnybrook Till, and late Wisconsinan Humber till, Halton Till, and Wildfield Till are interbedded with fossiliferous sediments equivalent to the Sangamonian Don Formation, early Wisconsinan Scarborough Formation (>50 ka BP), and middle Wisconsinan Thorncliffe Formation (45 ka BP). A complex periglacial record displays multistage fossil frost wedges, indicating intervals of severe climate in late Illinoian and early Wisconsinan time. Cored boreholes indicate deep gravel below and a till on Ordovician shale bedrock (Georgian Bay Formation). Vertebrates, molluscs, ostracodes, insects, and plants (diatoms, wood, seeds, pollen) indicate mostly cool conditions (boreal to tundra) for interstadial sediments. Interglacial conditions are represented by vertebrates, molluscs, and plants above York Till. Many taxa are new to the Quaternary of the Toronto area.À proximité de Woodbridge, au nord-ouest de Toronto, Ontario, une tranchée de chemin de fer de 15 mètres de haut et un banc d'emprunt dans le même dépôt, exploité pour la première fois en 1962, montre une séquence de tills multiples intercalée de sédiments fossilifères. Au cours des 35 années suivantes, les travaux révèlent que le till York (Illinoien), le till Sunnybrook (Wisconsinien précoce) et les tills Humber, Halton et Wildfield (Wisconsinien tardif) sont interlités avec des sédiments fossilifères équivalents à la Formation de Don (Sangamonien), la Formation de Scarborough (Wisconsinien précoce; >50 ka BP) et la Formation de Thorncliffe (Wisconsinien moyen; 45 ka BP). Des données périglaciaires complexes montrent de la gélifraction fossilifère à étages multiples, indiquant des intervalles de climat rigoureux à l'époque de l'Illinoien tardif et du Wisconsinien précoce. Des carottes de forage indiquent du gravier en profondeur et un till sur la roche-mère de schiste argileux de l'Ordovicien (Formation de Georgian Bay). Des vertébrés, des mollusques, des ostracodes, des insectes et des plantes (des diatomées, du bois, des graines et du pollen) indiquent des conditions climatiques surtout fraîches (boréales à toundra) pour les sédiments interstadiaires. Les conditions interglaciaires sont représentées par des vertébrés, des mollusques et des plantes au-dessus du till York. Plusieurs taxons sont nouveaux pour le Quaternaire de la région de Toronto.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The Lac Nominingue – Mont-Laurier region of the Central Metasedimentary Belt, Grenville Province of Quebec, comprises the granulite-facies Bondy gneiss complex (core of the Bondy gneiss dome) and overlying Sourd group metasedimentary rocks. A metamorphic foliation – transposed compositional layering (S[sub 1] ; host to peak-pressure parageneses) has been folded by isoclinal folds (F[sub 2] and F[sub 3] ) crosscut by leucosomes that host peak-temperature assemblages. The orthopyroxene isograd cuts obliquely across F[sub 3] folds, indicating that 1.20–1.18 Ga granulite-facies metamorphism post-dated D[sub 3] . D[sub 3] structures are cut by ductile shear zones and boudinaged in D[sub 4] and are folded by regional-scale, open, upright north–south folds (F[sub 5] ). Folds with shallowly dipping axial surfaces (F[sub 6] ) are subsequently developed in the Sourd group. F[sub 5] (and probably F[sub 6] ) developed prior to intrusion of the ca. 1165 Ma Chevreuil suite. In the Nominingue–Chénéville deformation zone (NCDZ) east of the Bondy gneiss dome, Chevreuil intrusions contain north-striking magmatic and tectonic foliations. These, along with host gneisses and metasedimentary rocks, are displaced by conjugate ductile shear zones (northeast dextral and south-southeast sinistral) and north-northeast-striking thrusts. Late open folds (F[sub 8] ) with east-northeast-striking axial surfaces produce dome and basin interference patterns. F[sub 2] to F[sub 5] folds may have formed during either subhorizontal, east–west contraction or east–west extension resulting from orogenic collapse or convective lithospheric thinning following crustal thickening during terrane assembly in the Elzevirian orogeny. Structures in the NCDZ imply ESE–WNW contraction and NNE–SSW (orogen-parallel) extension in D[sub 7] syn- to post-intrusion of the Chevreuil suite. F[sub 8] folds imply a late, Grenvillian SSE–NNW contraction.La région de Lac Nominingue – Mont-Laurier de la Ceinture métasédimentaire centrale, dans la Province de Grenville, au Québec, comprend le complexe gneissique de Bondy au faciès des granulites (coeur du dôme gneissique de Bondy) et les roches métasédimentaires sus-jacentes du Groupe du Sourd. Un litage de composition transposé et la foliation métamorphique (S[sub 1] ; hôte des paragenèses de pression maximale) ont été plissés isoclinalement (F[sub 2] et F[sub 3] ) et entrecoupés par des leucosomes qui comprennent les assemblages métamorphiques de température maximale. L'isograde de l'orthopyroxène coupe obliquement à travers les plis F[sub 3] , indiquant que le métamorphisme au faciès des granulites à 1,20 à 1,18 Ga, s'est produit après D[sub 3] . Les structures D[sub 3] sont recoupées par des zones de cisaillement ductiles et boudinées en D[sub 4] puis plissées par des plis nord-sud, droits, ouverts et d'échelle régionale (F[sub 5] ). Des plis de surface axiale à faible pendage (F[sub 6] ) se sont développés subséquemment dans le Groupe du Sourd. Les plis F[sub 5] (et probablement F[sub 6] ) précèdent la mise en place de la suite intrusive de Chevreuil, il y a environ 1165 Ma. Dans la zone de déformation de Nominingue–Chénéville (ZDNC), à l'est du dôme gneissique de Bondy, les intrusions de cette suite présentent des foliations magmatiques et tectoniques orientées nord-sud. Ces foliations et les roches hôtes gneissiques et métasédimentaires sont reprises par des zones conjuguées de cisaillement ductile (dextre NE et senestre SSE) et par du chevauchement à direction NNE. Des plis ouverts tardifs (F[sub 8] ) de surfaces axiales orientées ENE produisent des patrons d'interférence de type domes et bassins. Les plis F[sub 2] à F[sub 5] peuvent avoir été formés lors d'une contraction ou d'une extension est-ouest sub-horizontale résultant d'un effondrement orogénique ou encore lors d'un amincissement lithosphérique convectif après un épaississement de la croûte lors de l'assemblage de terranes durant l'orogène elzevirien. Les structures dans la ZDNC impliquent une contraction ESE–WNW et une extension NNE–SSW (parallèle à l'orogène) durant D[sub 7] qui a eu cours pendant et après la mise en place de la suite Chevreuil. Les plis F[sub 8] impliquent une contraction grenvillienne tardive SSE–NNW.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Comments on the article "Late Wisconsinan stratigraphy and chronology of southern St. George's Bay, Newfoundland: a re-appraisal," by T. Bell, D.G.E. Liverman, M.J. Batterson and K. Sheppard, which appeared in the 2001 issue of the "Canadian Journal of Earth Sciences." Details of the sedimentological model; Inventory and interpretation of glacial and associated sediments; Evidence in favor of a subaqueous origin of the sediments at Highlands.