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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.)

A 40.32 m piston core recovered from Effingham Inlet, on the west coast of Vancouver Island, provides the basis for a high-resolution geochemical study of the last deglaciation and the Holocene. Glacial retreat, basin isolation, sea-level rise, and productivity variations are determined using proxies for sediment composition (K/Al, Fe/Al, Mg/Al), grain size (Ti/Al, Zr/Al), sedimentary redox conditions (Mo/Al, U/Al), and productivity (wt.% organic carbon, wt.% opal). As local ice retreated and marine waters inundated the basin, coarse-grained glacimarine sediments were replaced by finer grained, laminated, opal-rich sediments. During meltwater pulse-1a, the dominance of local crustal rise over eustatic sea-level rise resulted in the progressive restriction of ocean circulation in Effingham Inlet and the formation of a temporary freshwater lake. The transition into stable Holocene conditions was initiated at ~12 700 BP, which corresponds to the onset of the Younger Dryas, as identified by the Greenland Ice core Project (GRIP) ice core δ18O record and was completed by 10 700 BP, ~800 years after the GRIP ice core record stabilized. Holocene Mo/Al and U/Al ratios range between 12–35 (×104) and 1–3.4 (×104), respectively, indicating that although large-amplitude, high-frequency fluctuations occur, the sediments of Effingham Inlet inner basin have remained organic rich and oxygen depleted for the entire Holocene period. The combination of anoxic bottom waters and a Holocene sedimentation rate of 217 cm/ka have preserved a high-resolution record of environmental change in the northeast Pacific over the last 11 000 years. Une carotte de 40,32 m, prélevée au moyen d’un carottier à piston au passage Effingham, sur la Côte Ouest de Vancouver, fournit la base pour une étude géochimique très détaillée de la dernière déglaciation et de l’Holocène. Le retrait glaciaire, l’isolement du bassin, l’élévation du niveau de la mer et les variations de productivité sont déterminés en utilisant des substituts pour la composition des sédiments (K/Al, Fe/Al, Mg/Al), la granulométrie (Ti/Al, Zr/Al), les conditions d’oxydoréduction sédimentaires (Mo/Al, U/Al) et la productivité (% poids carbone organique, % poids opale). À mesure que la glace locale se retirait et que les eaux marines inondaient le bassin, des sédiments glaciomarins à grain grossier étaient remplacés par des sédiments laminés, à grain plus fin et riches en opale. Durant un épisode important de montée du niveau marin global (meltwater pulse 1A), la dominance de la montée locale de la croûte par rapport à la hausse eustatique du niveau de la mer a progressivement restreint la circulation de l’océan dans le passage Effingham et a conduit à la formation d’un lac temporaire d’eau douce. La transition vers les conditions stables à l’Holocène a débuté vers 12 700 BP, ce qui correspond au début du Dryas récent, tel qu’identifié par les enregistrements de δ18O dans les carottes de glace du projet GRIP (« Greenland Ice Core Project ), et qui était terminé à 10 700 BP, soit environ 800 ans après la stabilization des enregistrements dans les carottes de glace du GRIP. À l’Holocène, les rapports Mo/Al et U/Al varient respectivement entre 12–35 (×104) et 1–3,4 (×104), indiquant que, malgré l’occurrence de fluctuations de grande amplitude et de fréquence élevée, les sédiments du bassin interne du passage Effingham sont demeurés riches en matières organiques et pauvres en oxygène pour toute la période de l’Holocène. La combinaison d’eaux de fond anoxiques et d’un taux de sédimentation de 217 cm/ka à l’Holocène a préservé l’enregistrement très détaillé du changement environnemental dans le Nord-Est du Pacifique au cours des derniers 11 000 ans. [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.)

Exposures in the Prophet River valley in northeast British Columbia provide a unique glimpse into the Quaternary history of the northwest Canadian Boreal Plains. The region shows evidence of Late Wisconsinan Laurentide glaciation in the form of widespread till, containing abundant erratic clasts derived from the Canadian Shield. Vertical sections along the Prophet River expose non-glacial and advance glacial sediments below this till. Pre-Late Wisconsinan non-glacial or interglacial floodplain sediments are interbedded with fluvial gravels at many sites. Macrofossils within horizontally laminated organic-rich black clay and silt indicate deposition on the floodplain of the paleo-Prophet River within an oxbow lake. The climate during deposition is interpreted to be similar to present, supporting a dominantly spruce forest. Wood obtained from eight sites provided non-finite radiocarbon ages, and one sample provided an age of 49 300 ±2000 BP, which is also considered non-finite. Glaciolacustrine clays and silts, deposited during impoundment of eastward-flowing drainage by the advance of the Laurentide Ice Sheet (LIS) in the Late Wisconsinan, overlie the non-glacial sediments throughout the valley. A blanket of clast-poor, clay-rich till up to 20 m thick, and deposited by the LIS, drapes the glaciolacustrine sediments. Since deglaciation, the Prophet River has incised the valley and formed fluvial terraces at different levels above the modern river. Des affleurements dans la vallée de la rivière Prophet dans le nord-est de la Colombie-Britannique offrent un coup d’œil unique sur l’historique du Quaternaire dans les plaines boréales du Nord-Ouest canadien. La région porte des preuves de la glaciation laurentidienne au Wisconsin tardif sous forme de till répandu contenant de nombreux clastes erratiques provenant du Bouclier canadien. Des coupes verticales le long de la rivière Prophet exposent des sédiments non glaciaires et des sédiments d’avancée glaciaire sous ce till. À de nombreux sites, des sédiments non glaciaires ou des sédiments de plaine d’inondation interglaciaire datant du pré-Wisconsin tardif sont interstratifiés avec les graviers fluviatiles. Des macrofossiles dans des laminations horizontales de silt et d’argile noire, riches en matière organique, indiquent une déposition sur la plaine d’inondation de la paléorivière Prophet dans un méandre mort. Lors de la déposition, le climat aurait été semblable au climat actuel, supportant une forêt où dominaient les épinettes. Du bois obtenu de huit sites fournissent des âges radiocarbone non finis et un échantillon a donné un âge de 49 300 ±2000 ans avant le présent, ce qui est aussi considéré non fini. Des argiles et des silts glacio-lacustres, déposés durant une retenue du drainage qui s’écoulait vers l’est par l’avancée de l’Inlandsis laurentidien au Wisconsinien tardif, reposent sur des sédiments non glaciaires à travers toute la vallée. Une couverture de till, pauvre en clastes et riche en argile, atteignant une épaisseur de 20 mètres et déposée par l’Inlandsis laurentidien, recouvre les sédiments glacio-lacustres. Depuis la déglaciation, la rivière Prophet a découpé la vallée et formé des terrasses fluviatiles à différents niveaux au-dessus de la rivière actuelle. [ABSTRACT FROM AUTHOR]

Two Cordilleran and three Laurentide glacial advances are recorded in Quaternary sediments and landforms in the Peace River valley, northeast British Columbia. The advances are inferred from fluvial gravels, glaciolacustrine sediments, and tills within nested paleovalleys excavated during three interglaciations and from the distribution of granitoid clasts derived from the Canadian Shield. Till of the last (Late Wisconsinan) Laurentide glaciation occurs at the surface, except where it is overlain by postglacial sediments. The advance that deposited this till was the most extensive in the study area, and the only advance definitively recognized in western Alberta south of the study area. Late Wisconsinan Cordilleran till has not been found in the study area, but Cordilleran and Laurentide ice may have coalesced briefly during the last glaciation. Support for this supposition is provided by the inferred deflection of Laurentide flutings to the southeast by Cordilleran ice. The earliest Laurentide advance may have been the least extensive of the three Laurentide events recognized in the study area. Erratics attributed to this advance occur only east of the Halfway River – Beatton River drainage divide. Deux avancées glaciaires de la Cordillère et trois de l’Inlandsis laurentidien sont évidentes dans les sédiments et la topographie du Quaternaire de la vallée de la rivière de la Paix, dans le nord-est de la Colombie-Britannique. Les avancées sont déduites à partir des graviers fluviatiles, des sédiments glacio-lacustres et des tills dans des paléovallées emboîtées excavées durant trois périodes interglaciaires et à partir de la distribution des clastes granitoïdes provenant du Bouclier canadien. Un till de la dernière glaciation laurentidienne (Wisconsinien tardif) se retrouve à la surface, sauf là où il est recouvert de sédiments post-glaciaires. L’avancée qui a déposé ce till a été la plus extensive dans le secteur à l’étude et c’est la seule avancée définitivement reconnue dans l’ouest de l’Alberta, au sud du secteur à l’étude. Aucun till de la Cordillère datant du Wisconsinien n’a été trouvé dans le secteur à l’étude. Cependant, la glace de la Cordillère et celle de l’Inlandsis laurentidien pourraient s’être unis durant une brève période au cours de la dernière glaciation. Cette hypothèse est soutenue par la déflexion inférée de rainures glaciaires laurentidiennes vers le sud-est par la glace de la Cordillère. L’avancée glaciaire laurentidienne la plus précoce pourrait être la moins étendue des trois événements laurentidiens reconnus dans le secteur à l’étude. Les blocs erratiques attribués à cette avancée ne se retrouvent qu’à l’est de la ligne de partage des eaux entre les rivières Halfway et Beatton. [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.)