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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.)

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.)

While the Cardium Formation (Turonian–Coniacian, Upper Cretaceous) is one of the major hydrocarbon sources, and consequently one of the most intensely studied siliciclastic formations in the Western Canada Sedimentary Basin, it remains one of the more controversial units in terms of understanding the depositional environments and processes it represents, and correlations between subsurface and outcrop. Proposed subsurface subdivisions based on sequence stratigraphic concepts, and relation of these allomembers to long-established members of the outcrop belt, have provoked further disagreements. The general lack of biostratigraphic data within the Cardium Formation makes it difficult to test different models and to resolve conflicting proposals. This paper provides stratigraphic and taxonomic information on all known scaphitid ammonoids from the Cardium Formation and correlation of these faunas with the Turonian and Coniacian zonal scheme established in the United States Western Interior; future publications will provide similar treatments of the collignoniceratid ammonites and inoceramid bivalves.Bien que la Formation de Cardium (Turonien–Coniacien; Crétacé supérieur) soit l'une des sources majeures d'hydrocarbures et, par conséquent, l'une des formations siliciclastiques les plus intensément étudiées du bassin sédimentaire de l'Ouest canadien, elle demeure l'une des unités les plus controversées en termes de compréhension des environnements et des processus de déposition qu'elle représente et des corrélations entre le roc souterrain et les affleurements. Les subdivisions proposées pour la subsurface, basées sur des concepts de séquences stratigraphiques, et les relations de ces allomembres à des membres de la ceinture d'affleurements établis depuis longtemps ont causé de nouvelles divergences d'opinion. Le manque de données biostratigraphiques à l'intérieur de la formation complique l'essai de différents modèles et la résolution de propositions contradictoires. Cet article fournit des informations stratigraphiques et taxonomiques sur tous les Ammonoïdés scaphitidae de la Formation de Cardium ainsi qu'une corrélation de ces faunes avec le schéma zonal du Turonien et du Coniacien établi dans l'Ouest américain intérieur; des publications à venir traiteront de façon similaire des Ammonites collignoniceratidae et des bivalves Inoceramidae.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Western North America preserves a rich record of Eocene life and environments under globally warm climates, and represents an interval where significant coal and other minerals were deposited. The Eocene is of interest to biologists and paleontologists for its record of the appearance and rise to dominance of many plant, insect, and mammal groups now typical of the temperate forests of North America, admixed with groups now well represented in tropical areas or restricted to eastern Asia. This record is also of interest for its potential contribution to our understanding of interactions between climate, the biota, and the ecosystems they occupied, under atmospheric carbon dioxide levels much higher than today. Documentation of the Eocene in western North America offers insights into the effects of future greenhouse climates. A special symposium held at the 2014 Annual Meeting of the Geological Society of America in Vancouver, British Columbia, brought together geologists, paleontologists, and biologists with an interest in these questions. This paper introduces the special issue that includes a selection of papers drawn from that symposium as well as on related topics, spanning the Early to Late Eocene, and geographically from British Columbia to Colorado. [ABSTRACT FROM AUTHOR]

Presents a reply to the comment given by I. Brookes to the article "Late Wisconsinan stratigraphy and chronology of southern St. George's Bay, Newfoundland: a re-appraisal," by Trevor Bell, David G.E. Liverman, Martin J. Batterson and Kevin Sheppard, which appeared in the 2001 issue of the 'Canadian Journal of Earth Sciences." Disagreements in field observations and interpretations; Discussion of a complex sedimentary sequences of interbedded diamicton, gravel and mud above the basal till; Discounting the significance of a date given to a diamicton at Highlands.

Infestation by the mountain pine beetle, Dendroctonus ponderosae, decimated the forests of central British Columbia from 1999 to 2012, severely impacting the forest industry of the Nechako-Chilcotin plateau. In response, all levels of government recognized the value in developing other areas of economic activity, such as hydrocarbon and mineral exploitation, to support local economies. Exploration for resources beneath the Nechako-Chilcotin plateau has historically been constrained by Tertiary volcanic sequences and Quaternary glacial deposits that obscure the underlying geology and limit geophysical imaging. Thus, a coordinated program comprising additional geological mapping, borehole data analysis, and modern geophysical surveys of the area was initiated in 2006, with the objective of better defining the subsurface geology, solving problems of imaging through the complex near-surface, and developing improved regional geological and tectonic models. An initial set of papers arising from this fieldwork, which focused on issues relevant to mineral and hydrocarbon exploration, was published in June 2011 in a Special Issue of the Canadian Journal of Earth Sciences. This Introduction to the second 'Mountain Pine Beetle' Special Issue summarizes a set of scientific papers that focus on topics more related to hydrocarbon exploration and the large-scale structure of the crust. The papers deal with the development, thickness, and present distribution of the most prospective Cretaceous sedimentary rocks, as well as characterizing the physical properties of the near-surface volcanic units. [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.)

The basal contact of the Sudbury Igneous Complex (SIC) on the North Range is interpreted as the outer edge of a meteorite impact crater. Yet, the base of the SIC, and contacts within the SIC, and the overlying Onaping are not circular. Their outline is elliptical. This and other details of the geology of the North Range which have not been fully explained include variations in the width of the metamorphic contact aureole, lateral discontinuous variations in the thickness of the norite and granophyre units, paleomagnetic evidence that the North Range contact of the SIC originally had a dip of around 20°, and differing magnetic fabrics in the norite/gabbro versus the granophyre. Several metrics are used to determine how much of the current outline of the North Range is the result of post-impact deformation and how much is a primary feature related to a meteorite impact. Uplift, rotation, and translation experienced by different segments of the North Range of the SIC are established using dyke azimuth and petrographic analysis of Matachewan diabase dykes, and paleomagnetic and magnetic fabric data analysis. These analyses show (a) the elliptical form of the North Range is a primary feature associated with a near-circular impact crater, (b) some of the original crater wall must have been preserved, and (c) deformation of the North Range is limited to regional scale block rotation producing a southwest dip modified by minor block rotation tilting and vertical displacement associated with north–northwest-trending faults. [ABSTRACT FROM AUTHOR]

This article presents a history of the development of U–Pb geochronology with emphasis on the role of Canadian researchers and some of its applications to Canadian geology. Modern U–Pb dating is the result of work by many individuals over the past 60 years, but the most important was Tom Krogh, who established methods that allowed determination of precise ages (<0.1% errors) on zircon using isotope dilution thermal ionization mass spectrometry. This was followed by the introduction of new analytical approaches by others, notably secondary ion mass spectrometry and laser ablation inductively coupled plasma mass spectrometry that allow intracrystal domains to be dated. U–Pb geochronology is now an indispensable tool for understanding the Earth. In collaboration with field mapping, it has vastly improved our understanding of the geological history of Canada as well as important geological events such as mass extinctions, secular changes in geological processes, and the birth of the solar system. [ABSTRACT FROM AUTHOR]

The area northeast of Sudbury, Ontario, is well known for hosting one of the largest unexplained geophysical anomalies in the Canadian Shield, the Temagami Anomaly. In search of a geological explanation for this anomaly, low-grade metamorphic ultrabasic dykes have been discovered in the overlying Huronian Supergroup sedimentary rocks, both in outcrop and in a deep drill core. Here, we report on the first geochemical and geochronological data obtained on these dykes and compare these data with known magmatic units in and around the 1850 Ma impact-generated Sudbury Igneous Complex (SIC). The NW-striking dykes, which cut across sedimentary rocks of the ca. 2.3 Ga Cobalt Group, and which are, in turn, crosscut by pseudotachylitic breccia, are characterized by distinctively high concentrations of Ti, P, Nb, and Zr, highly fractionated rare earth element patterns (La/YbN 7.6–15.5), and a lack of crustal contamination (Nb/Th > 10). Such features are typical of modern ocean island basalts but very different from Palaeoproterozoic rocks previously documented in the wider region. Multigrain U–Pb laser ablation inductively coupled plasma mass spectrometry analyses performed on magmatic titanite and apatite with high Th/U ratios yielded 1876.0 ± 8.7 and 1880.9 ± 8.3 Ma, respectively, which we interpret as the intrusion age of the dykes. This interpretation is supported by similar whole-rock Sm-Nd model ages of 1890–2000 Ma (initial εNd +2.5). This magmatic event in the footwall of the SIC shortly before the impact was coeval with, and likely genetically related to, the 1.88–1.87 Ga Circum-Superior Large Igneous Province. [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 Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Mackenzie Trough provides a high resolution signal for paleoceanography as a result of high sedimentation rates at the mouth of the Mackenzie River. Three cores were collected along a transect covering a depth range of 58–671 m and the time period of the last 11 500 cal BP. Prior to the last ~10 000 cal BP, the distal core is characterized by laminated sediment and a foraminiferal fauna of Arctic Bottom Water calcareous species and abundant planktic foraminifera suggesting little freshwater runoff and (or) perennial sea-ice cover. This occurs at a similar time as laminated sediments from the west of this site, which have been suggested to be part of the Lake Agassiz flood outburst and (or) cold period. If this outburst occurred, the very positive oxygen isotope values from our core (PC3; >+3.0 ppm) indicate that it did not flow through the Mackenzie Trough. After 9000 cal BP, the faunas in the three cores differ because of timing and different water depths. However, it is possible to see a progression of cold saline water prior to 10 000 cal BP, with a freshening of surface water after 10 000 cal BP where tintinnids (brackish water ciliates) occur with incursions of deep water Arctic calcareous species to ~3000 years BP. A sequence of mixed faunas appears as sea ice returns, at least periodically in the last 3000 cal BP; but (in core PC2 only) a return to more sea ice is recorded by both foraminifera and dinocysts in the last few hundred years. La fosse du Mackenzie fournit un signal à haute résolution pour la paléocéanographie en raison des taux élevés de sédimentation à l’embouchure de la rivière Mackenzie. Trois carottes ont été prélevées le long d’un transect couvrant une plage de profondeurs de 58 à 671 m; la période de temps couvre les derniers 11 500 années calendaires avant le présent (années cal. BP). Avant les derniers ~10 000 années cal. BP, la carotte distale est caractérisée par des sédiments laminés et une faune de foraminifères d’espèce calcaire des eaux du fond de la mer Arctique et les nombreux planctons foraminifères suggèrent peu d’écoulement d’eau douce et (ou) un couvert permanent de glace de mer. Cela se produit en même temps qu’une déposition de sédiments laminés à l’ouest de ce site; ces sédiments feraient partie du débordement de l’inondation et (ou) de la période froide du lac Agassiz. Si ce débordement a eu lieu, les valeurs très positives de l’isotope de l’oxygène de notre carotte (PC3; >+3,0 ppm) indiquent qu’il ne s’est pas écoulé à travers la fosse du Mackenzie. Après 9000 années cal. BP, les faunes dans les trois carottes diffèrent en raison des moments de déposition et des profondeurs d’eau différentes. Il est toutefois possible de voir une progression de l’eau froide saline avant 10 000 années cal BP. Après 10 000 années cal. BP, on note un adoucissement de l’eau de surface; en effet, des tintinnides (un cilié planctonique d’eau saumâtre) se retrouvent mélangés à des espèces calcaires d’eau profonde de l’Arctique jusqu’à ~3000 années BP. Une séquence mixte de faunes apparaît au retour de la glace de mer, du moins périodiquement, au cours des dernières 3000 années cal. BP. Cependant, un retour à plus de glace de mer est enregistré dans les foraminifères et les dinokystes au cours des quelques dernières centaines d’années (seulement dans la carotte PC2). [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.)

Presents a reply to the discussion made by R. Stea on the article "Late glacial stratigraphy and history of the Gulf of St. Lawrence," by H. Josenhans and S. Lehman, which appeared in the 1999 issue of the "Canadian Journal of Earth Sciences." Goals of the study; Interpretations of the IKU4 samples; Views on the high-water content and low consolidation of the upper glacial till-ice contact deposit.

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.)

Utilizing a combination of conodont-based biostratigraphy and geochemistry, the Frasnian–Famennian (F/F, mid-Late Devonian) boundary was located in the Long Rapids Formation, northern Ontario. It is present in a black shale sequence, 21.46 m above the base of the Long Rapids Formation, just above a carbonate bed that has similarities to the Upper Kellwasser Limestone, recognized as a lithological marker for the F/F boundary in Germany, Belgium, and France. There is no evidence of an impact event, and sedimentation across the boundary is continuous, although there is a discontinuity layer just below the boundary and the early part of the linguiformis Zone (of the standard Late Devonian conodont zonation) is missing. Strong positive δ [sup 13] C (organic and carbonate) values were identified and are interpreted as evidence of mass mortality in anoxic waters at the F/F extinction; positive δ[sup 18] O values suggest the extinction was also accompanied by a temperature drop. Negative δ[sup 34] S values also indicate anoxia, and negative δ[sup 15] N values provide evidence of reduced surface-water productivity. No iridium anomaly was found at the boundary, although higher than usual values were found about 85 cm below the F/F boundary. Sedimentological and biological evidence in the Long Rapids Formation indicates that the F/F extinction was coincident with major sea-level fluctuations in the late Frasnian, including a transgression beginning at the end of the linguiformis Zone and continuing through the Early triangularis Zone and beyond. Marine oscillations were accompanied by anoxia, which appears to be the killing mechanism for the conodont and other end Frasnian extinctions.La limite Frasnien–Famennien (F/F, Dévonien tardif moyen) a été localisée dans la Formation de Long Rapids, au nord de l'Ontario, en utilisant une combinaison de géochimie et de biostratigraphie basée sur les conodontes. Elle se trouve dans une séquence de shale noir, environ 21,46 m au-dessus de la base de la Formation de Long Rapids, juste au-dessus d'un lit de calcaire qui ressemble en bien des points au calcaire Kellwasser supérieur, lequel est reconnu comme un horizon repère lithologique pour la limite F/F en Allemagne, en Belgique et en France. Il n'y a pas d'évidence d'un événement d'impact et la sédimentation est continue à travers la limite, bien qu'il y ait une couche de discontinuité tout juste en dessous de la limite et que la partie précoce de la Zone à linguiformis (de la zonation standard pour les conodontes au Dévonien tardif) soit absente. Des valeurs fortement positives δ[sup 13] C (matières organiques et carbonates) ont été identifiées et elles sont interprétées comme évidence d'une mortalité de masse dans des eaux anoxiques à l'extinction F/F; des valeurs δ[sup 18] O positives portent à croire que l'extinction était accompagnée d'une chute de température. Des valeurs δ[sup 34] S négatives indiquent aussi l'anoxie et des valeurs δ[sup 15] N négatives fournissent des évidences de productivité réduite à la surface de l'eau. Aucune anomalie d'iridium n'a été trouvée à la limite, bien que des valeurs plus élevées que d'habitude aient été trouvées à environ 85 cm sous la limite F/F. Des évidences sédimentologiques et biologiques dans la Formation de Long Rapids indiquent que l'extinction F/F a coïncidé avec de grandes fluctuations du niveau de la mer au Frasnien tardif, incluant une transgression qui a débuté à la fin de la Zone à linguiformis et qui s'est poursuivie à travers et au-delà de la Zone à triangularis précoce. Les oscillations marines étaient accompagnées d'anoxie ce qui semble être le mécanisme qui ait tué les conodontes et celui responsable d'autres extinctions à la fin du Frasnien. [Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Four U–Pb dating sites straddling the Grenville front on the Labrador coast were investigated. Sites 1 and 2 exhibit complex intrusive, deformational, and metamorphic histories and were studied in detail, whereas two simpler outcrops (sites 3 and 4) were examined only at a reconnaissance level. At site 1, south of the Grenville front, a 1799[sup +3] [sub –2] Ma granodioritic gneiss is intruded by two phases of mafic dykes, then by a 1647[sup +7] [sub –5] Ma aplite and a ca. 1647–1500 Ma pegmatite, and lastly by the Michael gabbro. The pegmatite was metamorphosed at 1030 ± 10 Ma. Site 2 is on the Cut Throat Island thrust, which defines the Grenville front in the area. Early mylonitization occurred at 1790 ± 2 Ma, followed by 1730 ± 2 Ma pegmatite emplacement and then cooling at 1703 ± 15 Ma. A post-deformational melt pod gave a titanite age of 1662 ± 10 Ma. In the mylonitic host, based on positive correlation between Pb loss and degree of granularization in monazite, Grenvillian deformation was very short-lived. Sites 3 and 4 (north of the Cut Throat Island thrust), yielded 1709 ± 10 and 1726 ± 34 Ma ages, respectively. Lack of marked younger Pb loss demonstrates that these sites escaped both Labradorian and Grenvillian metamorphism. Emplacement, deformation, and (or) metamorphism occurred at 1800–1790 Ma, 1730–1700 Ma, 1660–1650 Ma, possibly at 1500 Ma, and at 1040–1030 Ma. The Cut Throat Island thrust was active during all events, but none was confined to it. The thrust marks the northern limit of Labradorian and Grenvillian orogenesis, but because similar pre-Labradorian history is preserved on both sides of the thrust, it is not a fundamental tectonic boundary after 1800 Ma. Nevertheless, because reactivation occurred during every geological orogenic event known in the region, it clearly represents a zone of persistent crustal weakness.Quatre sites de datations U-Pb chevauchant le front du Grenville sur la côte du Labrador ont été étudiés. Les sites 1 et 2 montrent des historiques complexes d'intrusion, de déformation et de métamorphisme et ils ont été étudiés en détail, alors que deux affleurements plus simples (sites 3 et 4) n'ont fait l'objet que d'une reconnaissance. Au site 1, au sud du front du Grenville, un gneiss à granodiorite, 1799[sup +3] [sub –2] Ma, est pénétré par deux phases de dykes mafiques, puis par une aplite, 1647[sup +7] [sub –5] , par une pegmatite vers 1647–1500 Ma et finalement par le gabbro Michael. La pegmatite a été métamorphosée vers 1030 ± 10 Ma. Le site 2 est situé sur le chevauchement Cut Throat Island, qui définit le front du Grenville dans la région. Une mylonitisation a eu lieu vers 1790 ± 2 Ma, suivie de la mise en place d'une pegmatite vers 1730 ± 2 Ma, puis il y a eu un refroidissement vers 1703 ± 15 Ma. Une lentille de fusion post-déformation a donné à de la titanite un âge de 1662 ± 10 Ma. Selon des corrélations positives entre la perte de Pb et le degré de granularité dans la monazite, la déformation du Grenville dans la roche mylonitique hôte a été de très courte durée. Les sites 3 et 4 (au nord du chevauchement de Cut Throat Island) ont donné des âges respectifs de 1709 ± 10 Ma et 1726 ± 34 Ma. Le fait qu'il n'y ait pas de perte de Pb nettement plus jeune démontre que ces sites ont échappé aux métamorphismes du Labrador et du Grenville. La mise en place et la déformation et/ou le métamorphisme ont eu lieu à 1800–1790 Ma, 1730–1700 Ma, 1660–1650 Ma, possiblement à 1500 Ma et à 1040–1030 Ma. Le chevauchement de Cut Throat Island était actif durant tous ces événements mais aucun ne lui était confiné. Le chevauchement marque la limite nord de l'orogène du Labrador et du Grenville mais, puisqu'un historique similaire pré-Labrador est préservé des deux côtés du chevauchement, il ne constitue pas une frontière tectonique fondamentale après 1800 Ma. Néanmoins, étant donné que de la réactivation a eu lieu durant chaque événement orogénique géologique connu dans la région, ce chevauchement représente clairement une zone de faiblesse crustale persistante.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

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]

The character of the Paleozoic basement of Quesnel Terrane and the position of the terrane accretion surface that separates Quesnel and Kootenay terranes from rocks of the ancient North American margin are subjects of debate. To address these problems, detailed mapping and U–Pb geochronologic studies were carried out in the Christina Lake area to define the relationship of the Mollie Creek assemblage, Josh Creek diorite, and Fife diorite to similar lithologies in the Greenwood – Grand Forks and Rossland regions, and to place limits on the ages of regional deformation and local position of the terrane accretion surface. Deformed metasedimentary rocks of the Mollie Creek assemblage may correlate with sedimentary rocks of the Pennsylvanian to Early Triassic Mount Roberts Formation in the Rossland area. The Mollie Creek assemblage is intruded by the foliated Late Triassic Josh Creek diorite. The Josh Creek diorite and Mollie Creek assemblage have been deformed together as a result of phase two deformation, following the intrusion of the Josh Creek diorite in the Late Triassic and prior to the intrusion of the Fife diorite and deposition of the overlying Rossland Group in the Early Jurassic. Based on relative age, structural position, and lithological similarities to other units within Quesnel Terrane, the Mollie Creek assemblage, Josh Creek diorite, and Fife diorite are a part of Quesnel Terrane and lie above the terrane accretion surface in the Christina Lake area. Therefore, Quesnel Terrane does not unconformably overlie basement rocks of known North American affinity in this region.Le caractère du socle paléozoïque du terrane de Quesnel et la position de la surface d'accrétion du terrane qui sépare les terranes de Quesnel et de Kootenay des roches de l'ancienne marge nord-américaine sont sujets à discussion. Afin d'aborder ces problèmes, de la cartographie de détail et des études géochronologiques U–Pb ont été entreprises dans la région du lac Christina afin de définir la relation entre l'assemblage de Mollie Creek, la diorite de Josh Creek, la diorite de Fife et des lithologies similaires dans les régions de Greenwood–Grand Forks et de Rossland et de circonscrire les âges de la déformation régionale ainsi que la position locale de la surface d'accrétion du terrane. Des roches métasédimentaires déformées de l'assemblage de Mollie Creek correspondent peut-être à des roches sédimentaires de la Formation de Mount Roberts (Pennsylvanien à Trias précoce) dans la région de Rossland. La diorite foliée de Josh Creek (Trias tardif) pénètre dans l'assemblage de Mollie Creek. La diorite de Josh Creek et l'assemblage de Mollie Creek ont été déformés ensemble à la suite d'une déformation de phase deux, après l'intrusion de la diorite de Josh Creek au Trias tardif et avant l'intrusion de la diorite de Fife et la déposition du Groupe de Rossland sus-jacent, au Jurassique précoce. Selon les âges relatifs, la position structurale et les similitudes lithologiques aux autres unités à l'intérieur du terrane de Quesnel, l'assemblage de Mollie Creek, la diorite de Josh Creek et la diorite de Fife font partie du terrane de Quesnel et reposent au-dessus de la surface d'accrétion du terrane dans la région du lac Christina. Le terrane de Quesnel ne repose donc pas en discordance sur les roches du socle d'affinité nord-américaine connue dans cette région.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The Quaternary stratigraphy of the Babine Lake region is characterized by a Late Wisconsinan succession of advance-phase glaciolacustrine sediments, glaciofluvial deposits, and till. Pollen data from a rare new interglacial site suggest a colder than present Middle Wisconsinan climate. Ice flow during the last glaciation was dominantly southeasterly, but in the Babine Range a regional, westerly ice-flow event occurred. Evidence for westerly flow diminishes eastward of Babine Lake, suggesting that the valley was near the eastward limit of an interior ice divide. Deglacial sediments include ice-marginal debris-flow, glaciofluvial, and glaciolacustrine sediments. Raised-delta elevations indicate that Glacial Lake Babine extended nearly 150 m above present lake level to 850 m asl, and higher, earlier phases may have existed locally. A variety of Holocene deposits cap the Quaternary succession. Glaciation has important implications for exploration in this copper-producing area. Southeasterly glacial dispersal patterns dominate, despite a regionally complex ice-flow history. Highly anomalous concentrations of copper occur in tills down-ice of most known bedrock copper occurrences, and a number of similarly anomalous till sites with no known copper sources have been identified in drift-covered areas. Exploration problems due to the thick and complex surficial cover can be overcome by selective sampling of basal tills, the composition of which clearly reflects the presence of buried mineral deposits. The effectiveness of till geochemistry as a method for locating buried mineralization in the region will be enhanced by careful selection of sample media and by a clear understanding of the glacial history.La stratigraphie du Quaternaire de la région du lac Babine est caractérisée par une séquence de sédiments glacio-lacustres de phase avancée, de dépôts fluvio-glaciaires et de till datant du Wisconsinien tardif. Des données de pollen d'un rare nouveau site interglaciaire suggèrent qu'au Wisconsinien moyen le climat était plus froid que présentement. Au cours de la dernière glaciation, l'écoulement de la glace était à prédominance sud-est mais, dans la chaîne Babine, il y eut un écoulement régional vers l'ouest. L'évidence pour un écoulement vers l'ouest diminue à l'est du lac Babine, suggérant que la vallée était près de la limite est d'une ligne intérieure de partage glaciaire. Des sédiments de déglaciation comprennent un écoulement de débris en marge du glacier, des sédiments fluvio-glaciaires et glacio-lacustres. Des élévations de deltas soulevés indiquent que le lac glaciaire Babine s'étendait près de 150 m au-dessus du niveau actuel du lac, à 850 m au-dessus du niveau de la mer, et que des phases plus précoces se sont retrouvées localement encore plus haut. Divers dépôts datant de l'Holocène reposent sur la séquence quaternaire. La glaciation a des implications importantes pour l'exploration dans cette région productrice de cuivre. Les patrons de dispersion glaciaire vers le sud-est dominent malgré un historique régional complexe d'écoulement glaciaire. Des concentrations hautement anomales de cuivre se retrouvent dans les tills en aval glaciaire de la plupart des occurrences connues du cuivre dans le roc et une nombre de sites également anomaux de tills ont été identifiées dans des régions recouvertes de dépôts morainiques sans qu'on puisse les relier à des dépôts connus de cuivre. Les problèmes d'exploration causés par le couvert épais et complexe peuvent être surmontés par un échantillonnage sélectif du till de fond dont la composition reflète clairement la présence de gisements minéraux enfouis. L'efficacité de la géochimie des tills comme méthode pour localiser de la minéralisation enfouie dans la région sera rehaussée par le choix judicieux des outils d'échantillonnage et par une bonne compréhension de l'historique glaciaire.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The Quaternary stratigraphy of the Nechako River – Cheslatta Lake area of central British Columbia is described and interpreted to reconstruct the late Quaternary history of the region. Exposures of glacial and nonglacial sediments deposited prior to the last glaciation (Fraser) are limited to three sites. Pollen assemblages from pre-Fraser nonglacial sediments at two of these sites reveal forested conditions around 39 000 BP. During the advance phase of the Fraser Glaciation, glacial lakes were ponded when trunk glaciers blocked some tributary valleys. Early in the glaciation, the drainage was free in easterly draining valleys. Subsequently, the easterly drainage was blocked either locally by sediments and ice or as a result of impoundment of the Fraser River and its tributaries east of the study area. Ice generally moved east and northeast from accumulation zones in the Coast Mountains. Ice flow was influenced by topography. Major late-glacial lakes developed in the Nechako River valley and the Knewstubb Lake region because potential drainage routes were blocked by ice.La stratigraphie du Quaternaire de la région de la rivière Nechako et du lac Cheslatta sise au centre de la Colombie Britannique est décrite et interprétée dans le but de reconstruire l'histoire du Quaternaire tardif de cette région. Seul trois coupes stratigraphiques mettent en évidence des sédiments glaciaires et non-glaciaires mis en place avant la dernière glaciation (Fraser). À deux sites, l'assemblage pollinique des sédiments non-glaciaires prédatant la Glaciation de Fraser reflète un environnement forestier aux environs de 39 000 BP. Lors de l'avancée des glaciers au début de la Glaciation de Fraser, des lacs glaciaires furent retenus dans les vallées secondaires par les glaciers qui occupaient les vallées primaires. Au début de cette glaciation, le drainage vers l'est fut tout d'abord ouvert mais subséquemment, il fut bloqué soit localement par des sédiments et de la glace ou en raison du blocage du fleuve Fraser et ses tributaires à l'est de la région d'étude. Les glaciers se sont écoulés vers l'est et le nord-est à partir de zones d'accumulation centrées sur la Chaîne Côtière. Les écoulements glaciaires furent influencés par la topographie. Des lacs post-glaciaires se sont formés dans la vallée de la rivière Nechako et dans la région du lac Knewstubb suite au blocage du drainage potentiel par la glace.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

New U–Pb ages and K–Ar dates, primarily for rocks proximal to mineral occurrences in the Fawnie Range of central British Columbia, document latest Cretaceous (ca. 74–66 Ma) continental-arc igneous activity and date associated base and precious metal mineralization. U–Pb ages of ca. 73–69 Ma for the Capoose pluton and hypabyssal to extrusive garnet rhyolites at the Capoose prospect demonstrate a latest Cretaceous age for mineralization and a likely plutonic source for mineralizing fluids. A U–Pb age of ca. 67 Ma for a late mineralized felsic dyke and two K–Ar dates (ca. 70 and 68 Ma) for hornfelsed Jurassic volcanic rocks at the Blackwater–Davidson prospect constrain a latest Cretaceous age for mineralization. A U–Pb age of ca. 74 Ma for a fine grained diorite sill that cuts a significant epithermal gold vein at the Tsacha prospect places a minimum age on mineralization at this probable Jura-Cretaceous deposit and documents latest Cretaceous magmatism. Latest Cretaceous K–Ar dates are reported for an andesite flow adjacent to the Eocene Holy Cross deposit (ca. 66 Ma), about 35 km north of the Fawnie Range, and a Kasalka Group rhyolite (ca. 68 Ma) exposed near the western margin of the Nechako Plateau. Latest Cretaceous magmatism and mineralization in the Fawnie Range represent the waning stages of Bulkley suite magmatism and porphyry-style mineralization, which was concentrated along the western margin of the Nechako Plateau at circa 88–70 Ma. The distribution of latest Cretaceous arc igneous rocks along the North American Cordilleran is reviewed and tectonic implications discussed.De nouveaux âges U–Pb et de nouvelles datations K–Ar, surtout pour des roches à proximité d'occurrences minérales dans la chaîne Fawnie du centre de la Colombie-Britannique documentent la plus récente activité ignée d'arc continental au Crétacé (ca. 74–66 Ma) et datent la minéralisation associée de métaux précieux et de métaux de base. Des âges U–Pb d'environ 73–69 Ma pour le pluton de Capoose et les rhyolites grenatifères hypabyssales à extrusives dans la zone d'intérêt Capoose démontrent un âge Crétacé terminal pour la minéralisation et une source plutonique probable pour les fluides minéralisateurs. Un âge U–Pb d'environ 67 Ma pour un dyke felsique à minéralisation tardive et deux datations K–Ar (ca. 70 et 68 Ma) pour des roches volcaniques au faciès des cornéennes, datant du Jurassique, à la zone d'intérêt Blackwater–Davidson limitent l'âge de la minéralisation au Crétacé terminal. Un âge U–Pb d'environ 74 Ma pour un filon-couche de diorite à grains fins qui recoupe une importante veine d'or épithermale à la zone d'intérêt Tsacha donne un âge minimum pour la minéralisation de ce dépôt, probablement au Jurassique–Crétacé, et documente le magmatisme au Crétacé terminal. Des datations K–Ar de Crétacé terminal sont rapportées pour un écoulement d'andésite adjacent au gisement de Holy Cross, datant de l'Éocène (ca. 66 MA), situé à environ 35 km au nord de la chaîne Fawnie et pour une rhyolite du Groupe de Kasalka (ca. 68 Ma) affleurant près de la bordure ouest du plateau Nechako. Du magmatisme et de la minéralisation dans la chaîne Fawnie, au Crétacé terminal, représentent les dernières phases du magmatisme de la suite Bulkley et de la minéralisation de type porphyrique, qui a été concentrée le long de la bordure ouest du plateau Nechako il y a environ 88–70 Ma. On passe en revue la distribution des roches ignées d'arc au Crétacé terminal le long de la Cordillère nord-américaine et on discute des implications tectoniques.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Presents a reply to the comment made by J.M. McLelland, J.W. Valley and E.J. Essene on the article "Very high temperature, moderate pressure metamorphism in the New Russia gneiss complex, northeastern Adirondack Highlands, metamorphic aureole to the Marcy anorthosite," by J. Alcock and P. Muller. Disagreements regarding the age of emplacements of the massif anorthosite relative to regional deformation; Discussion of zircon geochronology; Tests conducted on the model presented in the study.

Comments on the article "Late-glacial stratigraphy and history of the Gulf of Saint Lawrence," by H. Josenhans and S. Lehman, which appeared in the 1999 issue of the "Canadian Journal of Earth Sciences." Lithological data from IKU samples and glacial flow lines; Ice-extent reconstructions; Information on the relative sea-level history of the Gulf of Saint Lawrence.

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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.)