Search

The first (and second) baroclinic deformation (or Rossby) radii are presented and discussed north of ~60° N, focusing on deep basins and shelf seas in the high Arctic Ocean, the Nordic Seas, Baffin Bay, Hudson Bay and the Canadian Arctic Archipelago, derived from high-resolution ice-ocean general circulation model output. Comparison of the model output with measured results shows that low values of the Rossby radius (in shallow water) and high values (in the Canada Basin) are accurately reproduced, while intermediate values (in the region of the Makarov and Amundsen Basins) are overestimated. In the high Arctic Ocean, the first Rossby radius increases from ~5 km in the Nansen Basin to ~15 km in the central Canadian Basin. In the shelf seas and elsewhere, values are low (1-7 km), reflecting weak density stratification, shallow water, or both. Seasonality only strongly impacts the Rossby radii in shallow seas where winter homogenisation of the water column can reduce it to the order of 100 m. We also offer an interpretation and explanation of the observed scales of Arctic Ocean eddies. [ABSTRACT FROM AUTHOR]

The research activity described in this report is a comprehensive regional assessment of the impacts of climate change on water resources and options for adaptation in the Okanagan Basin. The ultimate goal of the project is to develop integrated climate change and water resource scenarios to stimulate a multistakeholder discussion on the implications of climate change for water management in the region. The paper describes two main objectives: (a) providing a set of research products that will be of relevance to regional interests in the Okanagan, and (b) establishing a methodology for participatory integrated assessment of regional climate change impacts and adaptation that could be applied to climate-related concerns in Canada and other countries. This collaborative study has relied on field research, computer-based models, and dialogue exercises to generate an assessment of future implications, and to learn about regional views on the prospects for adaptation. Along the way, it has benefited from strong partnerships with governments, researchers, local water practitioners, and user groups. Building on the scenario-based study components, and a series of interviews and surveys undertaken for the water management and adaptation case study components, a set of stakeholder dialogue sessions were organized which focused on identifying preferred adaptation options and processes for their implementation. Rather than seeking consensus on the "best" option or process, regional interests were asked to consider a range of available options as part of an adaptation portfolio that could address both supply side and demand side aspects of water resources management in the Okanagan. [ABSTRACT FROM AUTHOR]

Seasonal forest pools (SFPs) are geographically- and hydrologically-isolated ponded wetlands, in that they are topographically isolated from other surface waters. SFPs occur commonly throughout the temperate forests of the eastern United States and adjacent Canada. SFPs are ephemeral in occurrence, typically drying annually. The regular drying of SFPs excludes fish from these habitats, and as a result, they are the preferred breeding habitat of some amphibians, notably ambystomid (‘mole’) salamanders and wood frogs ( Rana sylvatica Le Conte). The pools also support a rich and diverse invertebrate fauna. The duration of the wet phase, or hydroperiod of SFPs, has been repeatedly shown to be the dominant influence on the composition and fitness of the faunal community of the pools. Despite the importance of SFP hydrology, it is a poorly studied subject. This paper reviews the limited state-of-knowledge of seasonal forest pool hydrology and associated basin morphology. The review discusses findings from studies of other isolated ponded wetlands that could be applicable to our understanding of the hydrology of SFPs. [ABSTRACT FROM AUTHOR]

Petrographic work on thin sections from rock samples collected in tight gas sandstones of the western Canada sedimentary basin (WCSB) shows that the sandstones are composed of intergranular, microfracture and slot, and isolated noneffective porosities. The petrographic observations of these triple-porosity rocks have led to a petrophysical interpretation with the use of a triple-porosity model. Tight gas reservoirs are very complex heterogeneous systems that have been evaluated in the past mostly with single-porosity models. We propose that these types of reservoirs can be represented better by triple-porosity models for more rigorous quantitative petrophysical characterization. The triple-porosity model discussed in this paper fits the petrographic observations very well, leading to a more rigorous characterization of effective and noneffective porosity. The petrographic and core-calibrated triple-porosity model is then used for well-log interpretation of those wells when these data are not available. The result is a reasonable quantitative characterization of the tight gas reservoir that can be used for improving hydraulic-fracturing design, flow-units determination, reservoir engineering, and simulation studies. The data can be determined at room conditions and simulated conditions of net stress. It is concluded that honoring with a triple-porosity model the different types of porosities observed in thin sections and cores leads to more-rigorous and -useful petrophysical interpretations that can be linked to gas productivity. [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.)

Summary: The ability to quantify and predict discharge and nutrient export patterns from agricultural catchments is confounded by the effects of antecedent hydrologic conditions (AHC) in upland areas. This paper examines the impacts of AHC on storm hydrologic response and nutrient export for 59 events measured over a 2-year period (year-round). Event-related discharge and nutrient (nitrate, phosphate) export were highly temporally variable. Runoff ratios ranged from 0 to 0.99 over the study period, with the lowest median runoff ratios being observed during the summer and early autumn period and the highest median runoff ratios being observed in March following snowmelt. Runoff ratios were positively correlated with AHC indices such as pre-event stream discharge (1-day) and antecedent (14-day) stream discharge although strong predictive relationships could not be generated (p >0.01). In general, runoff ratios increased throughout successive events as AHC became wetter; however trends observed among suites of events with having similar AHC did not produce similar patterns of hydrologic or nutrient export response, which clearly demonstrates the non-linear responses to variable AHC in the watershed. Basin nitrate (), total phosphorus (TP) and soluble reactive phosphorus (SRP) export varied with AHC in the basin, and flow-weighted mean nutrient concentrations (FWMC) ranged considerably (mean, range: 8, 1–18mgL−1 NO3–N; 18, 3–161μgL−1 SRP; 75, 15–274μgL−1 TP). Nutrient export increased with successive events when the basin was on a wetting trend, but decreased with successive events when the basin was on an overall drying trend. These patterns were linked to peak water table position during events and timing of fertilizer application. Overall, this work demonstrates that watershed hydrologic and nutrient export responses to precipitation and AHC are complex and cannot be predicted using simple linear relationships. This study also demonstrates the need to collect larger data sets when examining relationships between watershed hydrologic and nutrient export response. [Copyright &y& Elsevier]

Abstract: The geometry of a foreland basin is mainly a product of a complex dynamic balance between the orogenic loading, erosion and sedimentation, and lithospheric flexural response. To improve our understanding of the relationships between these processes and the foreland basin stratigraphy, a detailed stratigraphic and sedimentologic study of the Middle–Late Cenomanian Belle Fourche Formation in the subsurface of southern Alberta is presented in this paper. The Middle Cenomanian lower Belle Fourche Formation and the Late Cenomanian upper Belle Fourche Formation were deposited in underfilled conditions, showing prominent forebulge zones. It is demonstrated that during the Late Cenomanian with the cratonward migration of the uplifting forebulge zones, the axes of backbulge zones also migrated cratonwards and a wide uplifted forebulge zone was formed. During the last stage of the underfilled condition, the foreland basin had a relatively flat topography and fine sands were deposited along the flank of the uplifting forebulge. A qualitative model for the migration and stratigraphic fill of an underfilled foreland basin is proposed. This model provides a qualitative pattern of the cratonward migration of the forebulge zone and backbulge zone within a several-million-year tectonically-driven cycle. It is suggested that during the early underfilled period, the basin geometry is mainly controlled by the orogenic loading, and a prominent forebulge zone with an approximately fixed location is formed. During the late underfilled period, the basin geometry is mainly controlled by the sediment loading, and the forebulge zone move very fast along with the rapid cratonward shift of the sediment loading center. Over a longer time period and between different tectonically-driven cycles, along with the cratonward propagation of the thrusting wedge, the orogenic loading plays a more important role than the sediment loading for the migration of the forebulge zone. [Copyright &y& Elsevier]

Coalbed-methane (CBM) reservoirs commonly exhibit two-phase-flow (gas plus water) characteristics; however, commercial CBM production is possible from single-phase (gas) coal reservoirs, as demonstrated by the recent development of the Horseshoe Canyon coals of western Canada. Commercial single-phase CBM production also occurs in some areas of the low-productivity Fruitland Coal, south-southwest of the high-productivity Fruitland Coal Fairway in the San Juan basin, and in other CBM-producing basins of the continental United States. Production data of single-phase coal reservoirs may be analyzed with techniques commonly applied to conventional reservoirs. Complicating application, however, is the unique nature of CBM reservoirs; coal gas-storage and -transport mechanisms differ substantially from conventional reservoirs. Single-phase CBM reservoirs may also display complex reservoir behavior such as multilayer characteristics, dual-porosity effects, and permeability anisotropy. The current work illustrates how single-well production-data-analysis (PDA) techniques, such as type curve, flowing material balance (FMB), and pressure-transient (PT) analysis, may be altered to analyze single-phase CBM wells. Examples of how reservoir inputs to the PDA techniques and subsequent calculations are modified to account for CBM-reservoir behavior are given. This paper demonstrates, by simulated and field examples, that reasonable reservoir and stimulation estimates can be obtained from PDA of CBM reservoirs only if appropriate reservoir inputs (i.e., desorption compressibility, fracture porosity) are used in the analysis. As the field examples demonstrate, type-curve, FMB, and PT analysis methods for PDA are not used in isolation for reservoir-property estimation, but rather as a starting point for single-well and multiwell reservoir simulation, which is then used to history match and forecast CBM-well production (e.g., for reserves assignment). CBM reservoirs have the potential for permeability anisotropy because of their naturally fractured nature, which may complicate PDA. To study the effects of permeability anisotropy upon production, a 2D, single-phase, numerical CBM-reservoir simulator was constructed to simulate single-well production assuming various permeability-anisotropy ratios. Only large permeability ratios (> 16:1) appear to have a significant effect upon single-well production characteristics. Multilayer reservoir characteristics may also be observed with CBM reservoirs because of vertical heterogeneity, or in cases where the coals are commingled with conventional (sandstone) reservoirs. In these cases, the type-curve, FMB, and PT analysis techniques are difficult to apply with confidence. Methods and tools for analyzing multilayer CBM (plus sand) reservoirs are presented. Using simulated and field examples, it is demonstrated that unique reservoir properties may be assigned to individual layers from commingled (multilayer) production in the simple two-layer case. [ABSTRACT FROM AUTHOR]

The Fire Lake formation of the Yukon-Tanana terrane in the Finlayson Lake region, Yukon, Canada, consists primarily of Late Devonian (ca. 365–360 Ma) mafic metavolcanic rocks and smaller volumes of mafic and ultramafic subvolcanic metamorphosed intrusions. In this paper, field, geochemical, and Nd isotope attributes of these rocks are presented in an attempt to understand their tectonic setting, the magmatic processes involved in their formation, and their roles in Cordilleran crustal growth. The mafic rocks of the Fire Lake formation exhibit a wide diversity of geochemical signatures and are classified into seven chemically defined suites: (1) backarc-basin basalt, (2) enriched mid-oceanic-ridge basalt (E-MORB), (3) oceanic-island basalt (OIB), (4) Th-rich OIB, (5) boninite, (6) island-arc tholeiite, and (7) fight rare earth element (LREE)—enriched island-arc tholeiite. The diversity of geochemical signatures is interpreted to represent variable mixtures of asthenospheric (MORB-type) mantle, subarc mantle wedge, and lithospheric (OIB-type) mantle with or without elemental contributions from the subducted slab and/or continental crust. These suites of rocks are also associated with fine-grained basinal sedimentary facies, variations in metavolcanic and metasedimentary unit thickness, extensional synvolcanic faults, and apparent extensional-fault—controlled emplacement of mafic intrusive rocks and hydrothermal volcanic-hosted massive sulfide mineralization. The suites also exhibit a broad spatial distribution; those with “arc” signatures (Nb/Thmn. < 1; mn—normalized to primitive mantle values) are located primarily in the western parts of the formation, and suites with “nonarc” signatures (Sb/Thmn ≥ 1) are located primarily within the eastern parts of the formation. Collectively, these geologic and geochemical attributes are interpreted to stem from the transition from arc magmatism to the initiation of an extensional backarc basinal environment associated with an east-dipping subduction zone. The initiation of backarc-basin magmatism recorded in the Fire Lake formation was part of a much larger Late Devonian backarc basinal system forming along the western edge of the margin of North America. The Fire Lake formation is interpreted to represent (1) the commencement of Yukon-Tanana arc rifting and separation from the North American cratonic margin, and (2) the initiation of a marginal (backarc) basin (now the Slide Mountain terrane) inboard of the Yukon-Tanana arc system. This tectonic evolution likely occurred either as a result of slab rollback toward the west within the convergent margin responsible for Yukon-Tanana arc activity or as a result of the propagation of the Slide Mountain backarc-basin spreading ridges into the Yukon-Tanana arc system. This Yukon-Tanana arc rifting episode was also broadly coincident with rifting and hydrothermal activity within rocks of the North American craton. The geochemical and isotopic signatures of magmatic rocks in the Fire Lake formation have some features similar to intraoceanie arc rocks (e.g., boninites, island-arc tholeiites), and many have juvenile Nd isotope signatures (i.e., εNd(t) > 0; most have εNd(t) > +5), suggesting that the pericratonic terranes of the northern Cordillera have a significant juvenile component. If this is the case throughout the Yukon-Tanana terrane, then the pericratonic terranes may have contributed much more juvenile material to Cordilleran crustal growth in the Phanerozoic than has previously been considered. [ABSTRACT FROM AUTHOR]

Middle Ordovician to Middle Devonian carbonates in the Manitoba lowlands form an extensive aquifer system along the eastern edge of the Williston Basin. The aquifer is divided into fresh and saline portions by a series of topographic lows defined by major river systems and lakes that create a north–south-trending hydraulic divide. East of this divide Ca–Mg–HCO[sub 3] fresh waters are derived by active modern-day recharge focused in the Sandilands and Interlake regions. Stable isotope and geochemical data indicate that Na–Cl saline waters west of the divide are a mixture of original basin brines and glacial melt water pushed into the basin during Pleistocene glaciation. High Na/Cl and Cl/Br ratios are consistent with significant salt dissolution by glacial melt water.Des carbonates datant de l'Ordovicien moyen au Dévonien moyen dans les basses terres du Manitoba forment un vaste système aquifère le long de la bordure est du bassin de Williston. L'aquifère est divisé en portions d'eau douce et d'eau salée par une série de creux topographiques définis par les grands systèmes de rivières et de lacs qui créent une ligne de partage des eaux à tendance nord–sud. À l'est de cette ligne de partage, les eaux douces Ca–Mg–HCO[sub 3] proviennent de recharges actives contemporaines concentrées dans les régions de Sandilands et d'Interlake. Des données géochimiques et d'isotopes stables indiquent que les eaux salées Na–Cl à l'ouest de la ligne de partage sont un mélange des saumures du bassin original et de l'eau de fonte glaciaire qui a été poussée dans le bassin au cours de la glaciation au Pléistocène. Des rapports Na/Cl et Cl/Br élevés concordent avec une grande dissolution de sel par les eaux de fonte glaciaire.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Early Cretaceous unconsolidated quartz sand and kaolinitic clay deposits in the lowlands of Nova Scotia are preserved in narrow half-grabens obscured by glacial drift. The Chaswood Formation sediments can be subdivided into three members; upper and lower members dominated by cyclical sand–mud facies of fluvial origin and the middle member with lignitic clay of lacustrine origin. Ferruginous oxisols are common in the fine-grained facies of the upper and lower members. Seismic data indicate that Chaswood Formation strata in the Elmsvale Basin are deformed into steeply dipping faults and fault-related folds (Rutherford Road fault zone). An Aptian–Albian age for this tectonic event is inferred from synsedimentary deformation and from the angular unconformity spanning the Late Cretaceous and Tertiary that truncates the Chaswood Formation. Exhumation of a thick cover of Mesozoic sediment (1–2 km) is needed to account for the preservation of Chaswood Formation outliers after ~80 Ma of erosion. The half-grabens that host the Chaswood Formation were formed in the Mesozoic and were antecedent to the present-day structurally controlled lowlands.Des dépôts non consolidés de sable quartzeux et d'argile à kaolin (Crétacé précoce) dans les basses-terres de la Nouvelle-Écosse sont préservés dans d'étroits demi-grabens sous des dépôts glaciaires. Les sédiments de la Formation de Chaswood peuvent être subdivisés en trois membres : des faciès cycliques sable-boue d'origine fluviale dominent les membres inférieur et supérieur et de l'argile ligneuse d'origine lacustre domine le membre intermédiaire. Les faciès à grain fin des membres inférieur et supérieur comprennent fréquemment des oxisols ferrugineux. Des données sismiques indiquent que les strates de la Formation de Chaswook dans le bassin d'Elmsvale ont été déformées en failles à pendage abrupte et en plis reliés aux failles (zone de failles Rutherford Road). L'âge de cet événement tectonique (Aptien-Albien) est déduit de la déformation synsédimentaire et de la discordance angulaire couvrant le Crétacé tardif et le Tertiaire qui recoupe la Formation de Chaswood. Pour tenir compte de la préservation des lambeaux externes après ~80 Ma d'érosion, il faut l'enlèvement d'une épaisse couverture (1 à 2 km) de sédiments mésozoïques. Les demi-grabens hôtes de la Formation de Chaswood ont été formés au cours du Mésozoïque et ils précèdent les basses-terres actuelles qui sont contrôlées par la structure.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Focuses on the development and application of a regional flood frequency procedure based on canonical correlation analysis (CCA) from a northern Canadian basin in which floods are dominated by spring snowmelt. Neighborhood identification using CCA; Optimal number of stations in neighborhood; Phases of the general regionalization methodology.

The addition of an accurate pressure sensor to the inverted echo sounder (IES) has allowed for the development of a new method for calibrating the IES's acoustic travel-time record without the need for coincident conductivity-temperature-depth (CTD) or expendable bathythermograph profiles. Using this method, the round-trip travel-time measurement of the IES can be calibrated into various dynamic quantities with better accuracy than was possible with previous methods. For a set of four IES records from the Newfoundland Basin, the estimate of the accuracy of the geopotential height anomaly (integrated between 100 and 4000 db) calibrated from the IES measurements was reduced from 0.65 to 0.52 m[sup2] s[sup-2], which is a substantial reduction toward the intrinsic scatter of the geopotential height anomaly versus travel-time relationship for this region (0.42 m[sup2] s[sup-2]). The addition of the pressure sensor to the IES results in reduced errors and eliminates the need for coincident CTD measurements. Moreover, the pressure sensor provides a complementary dataset recording the changes of the barotropic pressure field. [ABSTRACT FROM AUTHOR]

Emerald Basin on the Scotian Shelf off Nova Scotia, Canada, is home to a globally unique aggregation of the glass sponge Vazella pourtalesi, first documented in the region in 1889. In 2009, Fisheries and Oceans Canada (DFO) implemented two Sponge Conservation Areas to protect these sponge grounds from bottom fishing activities. Together, the two conservation areas encompass 259 km2. In order to ascertain the degree to which the sponge grounds remain unprotected, we modelled the presence probability and predicted range distribution of V. pourtalesi on the Scotian Shelf using random forest modelling on presence-absence records. With a high degree of accuracy the random forest model predicted the highest probability of occurrence of V. pourtalesi in the inner basins on the central Scotian Shelf, with lower probabilities at the shelf break and in the Fundian and Northeast Channels. Bottom temperature was the most important determinant of its distribution in the model. Although the two DFO Sponge Conservation Areas protect some of the more significant concentrations of V. pourtalesi, much of its predicted distribution remains unprotected (over 99%). Examination of the hydrographic conditions in Emerald Basin revealed that the V. pourtalesi sponge grounds are associated with a warmer and more saline water mass compared to the surrounding shelf. Reconstruction of historical bottom temperature and salinity in Emerald Basin revealed strong multi-decadal variability, with average bottom temperatures varying by 8°C. We show that this species has persisted in the face of this climatic variability, possibly indicating how it will respond to future climate change. [ABSTRACT FROM AUTHOR]

Previous studies on unconformity-related uranium deposits in the Athabasca Basin (Canada) suggest that egress flow and ingress flow can develop along single fault systems at different stages of compressional deformation. This research aims to examine whether or not both ingress and egress flow can develop at the same time within an area under a common compressional stress field, as suggested by the reverse displacement of the unconformity surface by the basement faults. The study considers the Phoenix and Gryphon uranium deposits in the Wheeler River area in the southeastern part of the Athabasca Basin. Two-dimensional numerical modeling of fluid flow, coupled with compressional deformation and thermal effects, was carried out to examine the fluid flow pattern. The results show that local variations in the basement geology under a common compressional stress field can result in both egress and ingress flow at the same time. The fault zone at Phoenix underwent a relatively low degree of deformation, as reflected by minor reverse displacement of the unconformity, and egress flow developed, whereas the fault zone at Gryphon experienced a relatively high degree of deformation, as demonstrated by significant reverse displacement of the unconformity, and ingress flow was dominant. The correlation between strain development and location of uranium mineralization, as exemplified by Gryphon and Phoenix uranium deposits, suggests that the localization of dilation predicted by numerical modeling may represent favourable sites for uranium mineralization in the Athabasca Basin. [ABSTRACT FROM AUTHOR]

Background: We examined seven landslide dams and their changes over time in the Peace River region of Canada. These landslides had subchannel rupture surfaces in glacial and glaciolacustrine sediments. We assessed the stability of the dams using 6 separate, morphometric-based stability indices (with a total of 10 stability thresholds). Results: The landslides caused the streambeds to be elevated from 4 to 30 m forming the dams. The landslide lakes diminished in size over one to several years through stream incision into the dams and sediment infilling. The longest-lived dam persisted for up to 20 years. For two dams, incision into the dams lowered the lake levels by about half of the total depth, while the remainder of the water in the basins was displaced by sediment infilling. After the lakes drain, the sediment accumulations behind the dams can persist for decades. The stability analyses overpredicted unstable conditions which is inconsistent with the observed longterm persistence of the dams. Conclusions: The landslide dams in our study were relatively stable. Their lakes persisted for up to 2 decades and diminished over time through a combination of slow incision and basin infilling. The stability indices we assessed overpredicted unstable conditions and thus would require modification for these particular types of dams in this regional setting. [ABSTRACT FROM AUTHOR]

Heat flow high −80 ± 10 mW/m in the northern western parts of the Western Canadian foreland basin is in large contrast to low heat flow to the south and east (50 ± 7 mW/m) of the same basin with the same old 2E09 year's Precambrian basement and some 200-km-thick lithosphere. Over-thrusted and flat-laying sedimentary units are heated from below by heat flow from the old craton' crust and low 15 ± 5 mW/m mantle contribution. The heat flow vs. radiogenic heat production statistical relationship is not found for this area. To account for this large heat flow contrast and to have 200-km-thick lithosphere, we would need to assume that high heat production layer of the upper crust varies in thickness as much as factor of 2 and/or that the measured heat production at top of Precambrian basement is not representative for deeper rocks. The other explanation proposed before that heat in the basin is redistributed by the regional fluid flow systems driven from high hydraulic head areas close to the foothills of the Rocky Mountains toward low elevation areas to the east and north cannot be explained by observed low Darcy fluid velocities and the geometry of the basin. [ABSTRACT FROM AUTHOR]

Chinook Salmon Oncorhynchus tshawytscha return to the Yukon River in northwestern North America each summer, migrating to spawning destinations from the lower river to more than 3,000 km upstream. These returns support numerous fisheries throughout the basin. Despite a long history of fisheries research and management, there is no comprehensive account of Chinook Salmon spawning areas in the basin. To address this issue, we cataloged, summarized, and mapped the known spawning areas of Yukon River Chinook Salmon by using a variety of sources including published articles, gray literature, and information archived in agency databases. Most of our sources were published within the past 30 y, but some refer to observations that were recorded as long ago as the late 1800s. We classified spawning areas as major or minor producers with three indicators of abundance: 1) quantitative estimates of escapement (major producer if ≥500 fish, minor producer if <500 fish), 2) radiotelemetry-based proportions of annual production (major producer if ≥1% of the run, minor producer if <1% of the run), and 3) aerial survey index counts (major producer if ≥165 fish observed, minor producer if <165 fish observed). We documented 183 spawning areas in the Yukon River basin, 79 in the United States, and 104 in Canada. Most spawning areas were in tributary streams, but some were in main-stem reaches as well. We classified 32 spawning areas as major producers and 151 as minor producers. The Chinook Salmon spawning areas cataloged here provide a baseline that makes it possible to strategically direct abundance, biological sampling, and genetics projects for maximum effect and to assess both spatial and temporal changes within the basin. [ABSTRACT FROM AUTHOR]

Anastomosing rivers, systems of multiple interconnected channels that enclose floodbasins, constitute a major category of rivers for which various sedimentary facies models have been developed. While the sedimentary products of anastomosing rivers are relatively well-known, their genesis is still debated. A rapidly growing number of ancient alluvial successions being interpreted as of anastomosing river origin, including important hydrocarbon reservoirs, urge the development of robust models for the genesis of anastomosis, to facilitate better interpretation of ancient depositional settings and controls. The upper Columbia River, British Columbia, Canada, is the most-studied anastomosing river and has played a key role in the development of an anastomosing river facies model. Two hypotheses for the origin of upper Columbia River anastomosis include the following: (i) downstream control by aggrading cross-valley alluvial fans; and (ii) upstream control by excessive bedload input from tributaries. Both upstream and downstream control may force aggradation and avulsions in the upper Columbia River. In order to test both hypotheses, long-term (millennia-scale) floodplain sedimentation rates and avulsion frequencies are calculated using 14C-dated deeply buried organic floodplain material from cross-valley borehole transects. The results indicate a downstream decrease in floodplain sedimentation rate and avulsion frequency along the anastomosed reach, which is consistent with dominant upstream control by sediment overloading. The data here link recent avulsion activity to increased sediment supply during the Little Ice Age ( ca 1100 to 1950 ad). This link is supported by data showing that sediment supply to the upper Columbia study reach fluctuated in response to Holocene glacial advances and retreats in the hinterland. Upstream control of anastomosis has considerable implications for the reconstruction of the setting of interpreted ancient anastomosing systems. The present research underscores that anastomosing systems typically occur in relatively proximal settings with abundant sediment supplied to low-gradient floodplains, a situation commonly found in intermontane and foreland basins. [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.)

ABSTRACT The primary economic uranium (U) mineralization indicators in the Athabasca Basin are the reactivated prominent basement deformation zones, basement alteration halos, and the overlying sandstone alteration halos enveloping the deposit. High-resolution seismic surveys, from the Shea Creek area, are investigated to assess the potential of the surface seismic reflection technique for detecting these key mineralization markers. Four seismic profiles identify ductile to highly brittle deformation features of the basement. One of the brittle deformation features is a southwest-dipping prominent reactivated shear zone comparable to basement structures hosting other known deposits in the basin. The Carswell meteor impact structure is also a conspicuous component of the Shea Creek regional structural regime. The seismic sections identify several features of the impact structure, including recognition that the dimensions of this structure are significantly larger than those estimated by previous geological studies. This larger area includes both the Cluff Lake mine and the Shea Creek U deposits, and it reveals that the basement was considerably disturbed by the impact and suggests the reactivation of the southwest-dipping shear zone. Complex trace analysis of the seismic sections provides detailed information about the lateral changes in the reflectivity properties of the unconformity interval, which is another key zone of interest for uranium exploration. Based mainly on velocity information, several sub-zones of clay alteration and silicification were identified within prominent fracture depth intervals: both in the sandstone and the basement. Thus, this study documents that these primary mineral indicators can be detected by the seismic method. Cross-plots of velocity versus density of well log data identify changes in lithological units such as unaltered basement, fractured/altered basement, unaltered sandstone, clay alterations in sandstone, and silicification in sandstone. [ABSTRACT FROM AUTHOR]

Axel Heiberg Island (Arctic Archipelago, northern Nunavut, Canada) contains the thickest Mesozoic section in Sverdrup Basin (11 km). The ca. 370-km-long island is second only to Iran in its concentration of exposed evaporite diapirs. Forty-six diapirs of Carboniferous evaporites and associated minibasins are excellently exposed on the island. Regional anticlines, which formed during Paleogene Eurekan orogeny, trend roughly north on a regular ca. 20-km wavelength and probably detach on autochthonous Carboniferous Otto Fiord Formation evaporites comprising halite overlain by thick anhydrite. In contrast, a 60-km-wide area, known as the wall-and-basin structure ( WABS) province, has bimodal fold trends and irregular (<10 km) wavelengths. Here, crooked, narrow diapirs of superficially gypsified anhydrite crop out in tight anticline cores, which are separated by wider synclinal minibasins. We interpret the WABS province to detach on a shallow, partly exposed canopy of coalesced allochthonous evaporite sheets. Surrounding strata record a salt-tectonic history spanning the Late Triassic (Norian) to the Paleogene. Stratigraphic thinning against diapirs and spectacular angular unconformities indicate mild regional shortening in which diapiric roof strata were bulged up and flanking strata steepened. This bulging culminated in the Hauterivian, when diapiric evaporites broke out and coalesced to form a canopy. As the inferred canopy was buried, it yielded second-generation diapirs, which rose between minibasins subsiding into the canopy. Consistent high level emplacement suggests that all exposed diapirs inside the WABS area rose from the canopy. In contrast, diapirs along the WABS margins were sourced in autochthonous salt as first-generation diapirs. Apart from the large diapir-flanking unconformities, Jurassic-Cretaceous depositional evidence of salt tectonics also includes submarine debris flows and boulder conglomerates shed from at least three emergent diapirs. Extreme local relief, tectonic slide blocks, steep talus fans and subaerial debris flows suggest that many WABS diapirs continue to rise today. The Axel Heiberg canopy is one of only three known exposed evaporite canopies, each inferred or known at a different structural level: above the canopy (Axel Heiberg), through the canopy (Great Kavir) and beneath a possible canopy (Sivas). [ABSTRACT FROM AUTHOR]

Analyses of long-term records at 35 headwater basins in the United States and Canada indicate that climate change effects on streamflow are not as clear as might be expected, perhaps because of ecosystem processes and human influences. Evapotranspiration was higher than was predicted by temperature in water-surplus ecosystems and lower than was predicted in water-deficit ecosystems. Streamflow was correlated with climate variability indices (e.g., the El Niño-Southern Oscillation, the Pacific Decadal Oscillation, the North Atlantic Oscillation), especially in seasons when vegetation influences are limited. Air temperature increased significantly at 17 of the 19 sites with 20- to 60-year records, but streamflow trends were directly related to climate trends (through changes in ice and snow) at only 7 sites. Past and present human and natural disturbance, vegetation succession, and human water use can mimic, exacerbate, counteract, or mask the effects of climate change on streamflow, even in reference basins. Long-term ecological research sites are ideal places to disentangle these processes. [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.)

Intensification of the global hydrological cycle and increase in precipitation for some regions around the world, including the northern mid- to high latitudes, is expected in a changing climate. Changes in the amount of seasonal precipitation and the intensity and frequency of extreme precipitation events directly affect the magnitude of seasonal streamflows and the timing and severity of floods and droughts. In this study, the Canadian Regional Climate Model (CRCM) projected changes to streamflow characteristics (i.e., hydrologic regime, mean annual streamflows, and the timing, frequency, and magnitude of extreme flows-low and high) over selected basins in western Canada and assessment of errors associated with these characteristics in the current climate are presented. An ensemble of five current (1961-90) and five future (2041-70) simulations, corresponding to the Special Report on Emissions Scenarios (SRES) A2 scenario, are used in the assessment of projected changes; the ensemble of simulations allows better quantification of uncertainty in projected changes. Results of the study suggest an increase in the magnitude of winter streamflows and an earlier snowmelt peak for the northern basins. In addition, study of selected return levels of extreme flows suggest important changes to the timing, frequency, and magnitude of both low and high flows, with significant increases in 10-yr 15-day winter and fall low flows and 1-day high flows, for all the high-latitude west Canadian basins. The level of confidence in projected changes to mean annual streamflows is relatively higher compared to that for extreme flows for most of the basins studied. [ABSTRACT FROM AUTHOR]

More than a decade after the 1997 Red River Flood, vulnerability to future flooding exists due to a lack of risk communication. This study identifies risk communication gaps and discusses the creation of strategies to enhance information-sharing, bottom-up activity and partnership development. The objectives were achieved using mixed methods, including interviews, a floodplain-wide survey, and a decision-makers' risk management workshop. The results highlight a number of external pressures exerted by regional floodplain policies and procedures that restrict risk communication and affect social vulnerability in the rural floodplain. The failures of a top-down approach to floodplain management have impacted on communities' abilities to address floodplain risks, have amplified local risks, and have decreased community cooperation in floodplain management initiatives since the 1997 'Flood of the Century'. Recommended policies promote the establishment of community standards to compensate for gaps in risk communication and the development of partnerships between floodplain communities. [ABSTRACT FROM AUTHOR]

Like many high latitude areas, the mountainous region of subarctic Canada has experienced recent warming and is an area of large inter-annual temperature variations, most notably during the winter. Quantifying how climate tendencies affect streamflow, especially in the spring melt season, is critical not only to regional water resource management, but to understanding the influence of fresh-water on the Arctic sea-ice cover and global climate system. The impact of projected atmospheric warming on the discharge of the Liard River is unclear. Here, uncertainty in climate projections associated with GCM structure (2 °C prescribed warming) and magnitude of increases in global mean air temperature (1 to 6 °C) on the river discharge are assessed using a well-tested, semi-distributed hydrological model. Analyses have shown that the hydrological impacts are highly dependant on the GCM scenario. Uncertainties between the GCM scenarios are driven by the inconsistencies in projected spatial variability and magnitude of precipitation, rather than warming temperatures. Despite these uncertainties, the entire scenario simulations project that the subarctic nival regime will be preserved in the future, but the magnitude of change in river discharge is highly uncertain. Generally, spring freshet will arrive earlier, autumn to spring discharge will increase whereas summer flow will decrease, leading to an overall increase in annual discharge. [ABSTRACT FROM AUTHOR]

The Hudson Bay basin is the least studied of four major Phanerozoic intracratonic basins in North America and the mechanism by which it formed remains ambiguous. We investigate the crustal structure of Hudson Bay based on ambient-noise tomography, using 21 months of continuous recordings from 37 broad-band seismograph stations that encircle the Bay. Green's functions that emerge from the cross correlation of these ambient noise recordings are dominated by fundamental-mode Rayleigh waves. In the microseismic period band (5-20 s), these signals are most prominently expressed in certain preferred azimuths indicative of stationary coastal source regions in southern Alaska and Labrador. Seasonal variations are subtle but consistent with more energetic noise sources during winter months, when wave heights in the Pacific and north Atlantic are larger than in the summer. Noise emanating from Hudson Bay does not appear to contribute significantly to the cross correlograms. Group-velocity dispersion curves are obtained by time-frequency analysis of cross-correlation functions. We test and implement a signal-to-noise ratio (SNR) selection method for producing one-sided cross correlograms, which yields better-defined dispersion ridges than the standard two-sided averaging approach. Tomographic maps and cross sections obtained in the 5-40 s period range reveal significantly lower crustal velocities beneath Hudson Bay than in the bounding Archean Superior craton. The lowest mid-crustal velocities correspond to a previously determined region of maximum lithospheric stretching near the centre of the basin. Pseudosections extracted from the tomographic inversions along profiles across Hudson Bay provide the first compelling direct evidence for crustal thinning beneath the basin. Our results are consistent with a recent estimate of 3 km of crustal thinning, but not consistent with a proposed model for basin subsidence triggered by eclogitization of a remnant crustal root. [ABSTRACT FROM AUTHOR]

ABSTRACT The geometry of estuarine and/or incised-valley basins and their protected character compared with open sea basins are favourable for the preservation of sedimentary successions. The Lower St. Lawrence Estuary Basin (LSLEB, eastern Canada) is characterized by a thick (>400 m in certain areas) Quaternary succession. High- and very high-resolution seismic reflection data, multibeam bathymetry coverage completed by core and chronostratigraphic data as well as a 3-D seismic stratigraphic model are used to document the geometrical relationships between the bedrock and the Quaternary units of the LSLEB. The bedrock geometry of LSLEB is characterized by two large troughs that are interpreted as resulting mainly from repeated (?) periods of glacial overdeepening of a pre-Quaternary drainage system. However, other mechanisms with complex feedback effects such as differential glacio-isostatic uplift, erosion, sedimentary supply, and subsidence may have contributed to the formation of bedrock troughs. The two large bedrock troughs are mostly filled by ∼200 m thick Wisconsinan (Marine Isotopic Stages 2-4) and possibly older sediments. Overlying units recorded the retreat of the Laurentian Ice Sheet during the Late Wisconsinan (Marine Isotopic Stage 2) and estuarine conditions during the Holocene. The strong correlation existing between the bedrock topography and the thickness of the Quaternary succession is indicative of the effectiveness of the LSLEB as a sediment trap. [ABSTRACT FROM AUTHOR]

Nares Strait separating Greenland and northernmost Canada is floored by continental crust. Most palaeogeographic reconstructions of Laurentia and the North Atlantic region model the seaway as the site of massive sinistral strike–slip and/or compression/transpression, subduction and collision, the supposed manifestations of the hypothetical Wegener Fault. However, these reconstructions fail to take into account the bedrock geology that represents within-plate evolution. Both sides of Smith Sound, the southernmost part of Nares Strait, expose the same early Proterozoic to early Palaeozoic assemblages that are unaffected by seaway-related tectonism or thermal activity. Smith Sound is an intact crustal block or `linchpin' demonstrating that there was no independent Greenland plate. North-west Greenland was not a leading plate margin neither was Nares Strait the site of the plate boundary between Greenland and North America. The Wegener Fault does not exist. The Smith Sound linchpin constitutes a key constraint that must be respected in any palaeogeographic reconstruction of the region. [ABSTRACT FROM AUTHOR]

The article reports on the hillslope runoff from a forested peat plateau in a discontinous permafrost basin in Northwest Territories, Canada. A water balance approach and the Dupuit-Forchheimer equation were used to quantify sub-surface runoff wherein results showed that runoff reported for about half of moisture loss from the peat plateau occurred in response to snowmelt inputs. Soil moisture conditions before soil freezing were a major factor in controlling the volume of hillslope runoff. Minimal lag between rain events and hydrograph response suggests that most of the runoff is rapidly transported to wetlands.

The performance of different models and procedures for forecasting aggregated May–July streamflow for the Churchill Falls basin on the Québec-Labrador peninsula is compared. The models compared have different lead times and include an autoregressive model using only past streamflow data, an autoregressive with exogenous input model utilizing both past streamflow and precipitation, and a linear regression model using the principal components of exogenous measures of atmospheric circulation inferred from the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis project. The forecast skills of the different approaches are compared using a variety of measures of performance. The results indicate that relatively accurate forecasts using only measures of atmospheric circulation can be issued as early as in December of the prior year. A multimodel combination approach is found to be more effective than the use of a single forecast model. In addition, it is concluded that forecasting models utilizing atmospheric circulation data are useful, especially for basins where hydroclimatic observations are scarce and for basins where flows and other hydroclimatic variables are not strongly autocorrelated (do not depend on their past). [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.)

Holocene histories of two polygonal peatlands in the low arctic of south-central Nunavut, Canada, are reconstructed using plant macrofossil and pollen stratigraphies of four cores. Peat accumulation began in both basins between 7600 and 8000?cal. yr BP, within less than 1000 years after deglaciation. Mid- to late-Holocene vegetation changes recorded in the peat cores may be related to permafrost aggradation, associated with a regional cooling trend inferred from a nearby lake sediment record. However, differences in the timing of changes among the peatland coring sites indicate that local autogenic processes have also played an important role. Peat accumulation rates have decreased considerably in the past 3000 to 5000 years compared to the early Holocene. Our results illustrate the complexity of peatland development and peat accumulation dynamics in areas of permafrost, resulting from the important influences of both internal autogenic factors and external environmental forces such as climatic change. [ABSTRACT FROM AUTHOR]

Bracketing ages on marine-freshwater transitions in isolation basins extending from sea level to 100 m elevation on Lasqueti Island, and data from shallow marine cores and outcrops on eastern Vancouver Island, constrain late Pleistocene and Holocene sea-level change in the central Strait of Georgia. Relative sea level fell from 150 m elevation to about -15 m from 14 000 cal. yr BP to 11 500 cal. yr BP. Basins at higher elevations exhibit abrupt changes in diatom assemblages at the marine-freshwater transition. At lower elevations an intervening brackish phase suggests slower rates of uplift. Relative sea level rose to about +1 m about 9000 cal. yr BP to 8500 cal. yr BP, and then slowly fell to the modern datum. The mean rate of glacio-isostatic rebound in the first millennium after deglaciation was about 0.11 m a -1 , similar to the peak rate at the centres of the former Laurentide and Fennoscandian ice complexes. The latter feature smooth, exponential-style declines in sea level up to the present day, whereas in the study area the uplift rate dropped to less than one-tenth of its initial value in only about 2500 years. Slower, more deeply seated isostatic recovery generated residual uplift rates of <0.01 m a -1 in the early Holocene after the late-Pleistocene wasting of the Cordilleran ice sheet. [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.)

Sedimentary basins are suitable to different degrees for CO2 geological sequestration as a result of various intrinsic and extrinsic characteristics, of which the geothermal regime is one of the most important. Warm basins are less favorable for CO2 sequestration than cold basins because of reduced capacity in terms of CO2 mass, and because of higher CO2 buoyancy, which drives the upward CO2 migration. A set of 15 criteria, with several classes each, has been developed for the assessment and ranking of sedimentary basins in terms of their suitability for CO2 sequestration. Using a parametric normalization procedure, a basin's individual scores are summed to a total score using weights that express the relative importance of different criteria. The total score is ranked to determine the most suitable basin or region thereof for the geological sequestration of CO2. The method is extremely flexible in that it allows changes in the functions that express the importance of various classes for any given criterion, and in the weights that express the relative importance of various criteria. Examples of application are given for Canada's case and for the Alberta basin in Canada. [ABSTRACT FROM AUTHOR]

Comparison of litho-, bio-, and chemostratigraphy in two cores from the northeastern margin of the Michigan Basin (Manitoulin Island) and from within the Ottawa Embayment (eastern Ontario) identifies interbasinal differences of Late Ordovician platform foundering linked to Taconic orogenesis. Graptolite biostratigraphy defines an east-to-west younging (late Edenian to early Maysvillian) of platform burial. A regional unconformity likely caps the platform succession. In both basins, an increased supply of mafic material appears during the final stages of platform collapse, with the accumulation of organic-rich (<8%), petroliferous shales (Collingwood Member -- Michigan Basin; Eastview Member -- Ottawa Embayment). Both units preserve evidence for deposition coincident with increased dysoxic to possible anoxic bottom-water conditions, but the Collingwood Member accumulated under a relatively stable paleoceanographic environment. Rhythmic interbedding with platform limestone in eastern Ontario, combined with evidence for fluctuating paleoproductivity, suggests the depositional environment of the Eastview Member was more sensitive to higher order controls affiliated with tectonic, oceanographic, and (or) sea level variation. Such interbasinal differences likely reflect a greater rate of subsidence in the Manitoulin region transforming platform sedimentation to a distal ramp facies. In eastern Ontario, a lesser rate of subsidence maintained a shallower water, but open margin, setting. Burial of the Upper Ordovician platform, as preserved in eastern Ontario, occurred during peak dysoxic conditions, with deposition of a hemipelagic facies (Billings Formation) that marks the peak supply of clay-size mafic-derived sediment. Bottom-water ventilation occurred only with appearance of abundant Taconic-derived distal turbidites. An equivalent hemipelagic facies appears to be absent from the Manitoulin region. However, equivalent resedimented deposits are represented by the Blue M [ABSTRACT FROM AUTHOR]

Distribution of facies in the lower half of the Bylot Supergroup suggests overall westward deepening of the Mesoproterozoic Borden Basin. In marked contrast, the upper half of the succession records a reversal in the overall bathymetric trend, such that the eastern portion underwent relative deepening as the west experienced relative shallowing. Strata deposited during this reversal belong to the Victor Bay Formation, a ramp composed predominantly of limestone. Karsting of carbonate strata and development of an angular unconformity in the west contrast with back-stepping and drowning of the ramp in the east, followed by mantling by deep-water limestone, carbonaceous carbonate, and turbidites. Increased accommodation space during this time, via both tectonic subsidence and eustatic sea-level rise, led to a profusion of stromatolite pinnacle reefs and large biostromes. The reversal of basin polarity is best reconciled with development of a distal foreland basin superimposed on the Borden aulacogen. Crustal rethickening and uplift occurred along reactivated basement faults during an eastward-directed compressional event and could be related to thrusting of similar age and vergence in the Coppermine River Group of northwestern Canada.La distribution des faciès dans la moitié inférieure du Supergroupe de Bylot suggère un approfondissement général vers l'ouest du bassin de Borden (Mésoprotérozoïque). Par contre, la moitié supérieure de la séquence montre un renversement de la tendance bathymétrique, de telle façon que la partie orientale subissait un approfondissement relatif alors que la partie occidentale subissait un rehaussement relatif. Les strates déposées au cours de ce renversement appartiennent à la Formation de Victor Bay, une rampe composée surtout de calcaire. Le développement de karsts dans les strates calcareuses et le développement d'une discordance angulaire à l'ouest contrastent avec la rétrogradation et l'ennoiement de la rampe à l'est, suivi d'un recouvrement par des calcaires d'eau profonde, des carbonates carbonés et des turbidites. Durant ce temps, une augmentation de l'espace disponible, grâce à la subsidence tectonique et à l'élévation eustatique du niveau de la mer, a conduit à une profusion de récif-pinacles à stromatolites et à de vastes biostromes. L'inversion de la polarité du bassin concorde très bien avec le développement d'un bassin d'avant-pays distal surimposé à l'aulacogène de Borden. Un nouvel épaississement et un rehaussement de la croûte se sont produits le long de failles du socle réactivées lors d'un événement de compression dirigé vers l'est et qui pourrait être relié à un chevauchement d'âge et de vergence similaires dans le Groupe de Coppermine River du nord-ouest du Canada.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Upper Carboniferous (Stephanian) coal measures of the Sydney Basin are deformed by reverse faults and folds with dips of up to 50° on the limbs. These structures represent compressional or transpressional events (Donkin Episode) of unknown sequence and timing. Offshore swath-bathymetry data indicate that northwest-striking reverse faults are folded by prominent northeast-trending folds. Vitrinite reflectance patterns of oriented coal samples from the fold limbs are uniaxial negative, with minimum reflectance axes (R[sub min] ) near-normal to bedding and fanning across fold axes. This pattern implies that the bulk of coalification took place through burial compaction without directed horizontal stress, prior to the deformation that produced the folds. Slight divergence between R[sub min] axes and poles to bedding may reflect slight tilting, associated with differential subsidence or early reverse faulting, before or during coalification, or may lie within analytical error. One moderately biaxial sample suggests that some deformation accompanied coalification locally. Available apatite fission-track data for the Sydney Basin indicate that cooling of the coal measures to below 100 ± 20°C was underway by the Middle to Late Triassic or earlier. Because cooling implies that coalification was largely complete, the fission-track results are compatible with latest Paleozoic or early Mesozoic deformation. We infer that the Donkin Episode represents late Alleghanian (Permian?) compression within the Appalachian Orogen. If so, the Sydney structures are manifestations of a little-known tectonic episode in Atlantic Canada. However, Mesozoic–Cenozoic deformation cannot be ruled out.Les séries houillères du bassin de Sydney (Carbonifère supérieur - Stéphanien) sont déformées par des failles inverses et des plis déversés dont les flancs atteignent des pendages de 50º. Ces structures représentent des événements de compression ou de transpression (épisode Donkin) dont la séquence et la synchronisation sont inconnues. Les données de bathymétrie par secteurs au large indiquent que les failles inverses à direction nord-ouest sont pliées par des plis proéminents à tendance nord-est. Les patrons du facteur de réflexion de la vitrinite provenant d'échantillons de charbon orientés prélevés sur les flancs des plis sont uniaxes négatifs, avec des axes de réflectance minimum (R[sub min] ) presque perpendiculaires au litage et se dispersant en travers des axes de plis. Ce patron implique que la plus grande part de la carbonisation a eu lieu par compaction d'enfouissement sans contrainte horizontale directe, avant la déformation qui a produit les plis. La légère divergence entre les axes R[sub min] et les pôles du litage pourrait refléter un léger basculement associé à une subsidence différentielle ou à des failles inverses précoces, avant ou durant la carbonisation, ou encore cette divergence pourrait être à l'intérieur de la fourchette de l'erreur analytique. Notre échantillon modérément biaxe suggère qu'une certaine déformation ait localement accompagné la carbonisation. Pour le bassin de Sydney, les données disponibles de datation par traces de fission sur l'apatite indiquent que le refroidissement des séries houillères à des températures inférieures à 100 ± 20 ºC était déjà en cours au Trias moyen à tardif ou plus tôt. Puisque le refroidissement implique que la carbonisation était presque terminée, les résultats de datation par traces de fission concordent avec la déformation au Paléozoïque terminal ou au Mésozoïque précoce. Nous concluons que l'épisode Donkin représente une compression à l'Alléghanien tardif (Permien ?) à l'intérieur de l'orogène des Appalaches. Si tel est le cas, les structures de Sydney sont des évidences d'un épisode tectonique peu connu au Canada Atlantique. Cependant, une déformation au Mésozoïque–Cénozoïque ne peut être rejetée d'emblée.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The Paleoproterozoic Thelon Basin, located on the border between Nunavut and the Northwest Territories of Canada, is a contemporaneous analog of the uranium-rich Paleoproterozoic Athabasca Basin in Canada. Early diagenesis resulted in precipitation of extensive hematite on the surfaces of detrital quartz grains throughout the Thelon Formation and minor hydroxy-phosphate in veins locally. Continued diagenesis then resulted in syntaxial quartz cementation of detrital quartz at 130°C from fluids having ca. 17 wt.% equivalent NaCl, similar to the Athabasca Basin. Cementation of this type is most pronounced in fine-grained sequences in the Thelon Basin. A period of extensive desilicification during continued burial was followed by formation, at ca. 200°C, of peak-diagenetic illite having Ar–Ar ages of ca. 1400–1690 Ma in the Thelon Formation. This illite was associated with fluids with δ[sup 18] O and δD values of ca. 6‰ and –50‰, respectively, similar to those during peak diagenesis of the Athabasca Basin. Although the timing, salinity, and isotopic composition of the peak-diagenetic fluids in the Thelon and Athabasca Basins are similar, the peak-diagenetic mineral assemblage in the Athabasca Formation is dickite and illite, with minor dravite and goyasite rather than simply illite. Consequently, the fluids at peak diagenesis, which in the Athabasca Basin are synchronous with formation of world-class unconformity-type uranium deposits, had different compositions in each basin. Post-peak diagenesis in the Thelon Basin was quite distinct from that in the Athabasca Basin in that illite was replaced in the central portion of the basin by K-feldspar and then sudoite, which crystallized from saline brines at ca. 1000 Ma and 100°C. Evidence for later infiltration of these brines is absent in the Athabasca Basin, although uranium mobilization at ca. 900 Ma from fluids having the same characteristics as those at peak diagenesis was pronounced in the Athabasca Basin. Recent incursion of meteoric waters along reactivated structures into the Athabasca Basin has variably affected hydrous and uraniferous minerals, but evidence for this is lacking in the Thelon Basin. The Thelon Basin reflects less intensive fluid–rock interaction in its early history than that recorded in the basal units of the Athabasca Basin.Le bassin de Thelon (Paléoprotérozoïque), situé sur la frontière entre le Nunavut et les Territoires du Nord-Ouest du Canada, est l'analogue contemporain du bassin riche en uranium d'Athabasca (Paléoprotérozoïque), au Canada. Une diagenèse précoce a fait précipiter une grande quantité d'hématite sur les surfaces des grains de quartz détritique à travers toute la Formation de Thelon et, localement, une faible quantité d'hydroxy-phosphate dans les veines. La poursuite de la diagenèse a ensuite résulté en la cémentation quartzique par surcroissance du quartz détritique à 130 ºC à partir de fluides qui avaient environ 17 % (poids) d'équivalent NaCl, semblable au bassin d'Athabasca. La cémentation de ce type est le plus prononcé dans les séquences à grains fins du bassin de Thelon. Une période de désilicification extensive, au cours d'un enfouissement continu, a été suivie de la formation d'illite au sommet de la diagenèse, à environ 200 ºC; les âges Ar–Ar de l'illite sont d'environ 1400–1690 Ma dans la Formation de Thelon. Cette illite était associée à des fluides ayant des valeurs de δ[sup 18] O et δD d'environ 6‰ et – 50 ‰ respectivement, semblables a celles présentes durant le sommet de la diagenèse du bassin d'Athabasca. Bien que la séquence, la salinité et la composition isotopique des fluides au sommet de la diagenèse dans les bassins de Thelon et d'Athabasca soient semblables, l'assemblage minéralogique du sommet de la diagenèse dans la Formation de l'Athabasca consiste en dickite et en illite avec de la dravite et de la goyasite plutôt que simplement de l'illite. Par conséquent, les fluides au sommet de la diagenèse, lesquels dans le bassin d'Athabasca sont synchrones à la formation de dépôts d'uranium de classe mondiale et de type discordance, ont des compositions différentes dans chaque bassin. Dans le bassin de Thelon, la diagenèse après le sommet a été assez différente de celle dans le bassin d'Athabasca en ce que l'illite dans la partie centrale du bassin a été remplacée par un feldspath-K puis par de la sudoïte, qui a cristallisé à partir de saumures vers 1000 Ma et à 100 ºC. Il n'existe aucune preuve d'une infiltration postérieure de ces saumures dans le bassin de l'Athabasca, bien que la mobilisation de l'uranium, vers 900 Ma et à partir de fluides ayant les mêmes caractéristiques, ait été forte dans le bassin de l'Athabasca. Une récente incursion d'eaux météoriques dans le bassin de l'Athabasca, le long de structures réactivées, a affecté les minéraux hydratés et uranifères à divers degrés, mais il n'y a pas d'évidence de cela dans le bassin de Thelon. Le bassin de Thelon reflète une interaction fluide–roche moins intense au début de son histoire que celle enregistrée dans les unités à la base du bassin de l'Athabasca.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

ABSTRACT A hydrographic survey was performed in January-February 1997 to document the winter circulation of the North Atlantic Current system in the Newfoundland Basin, as part of the Fronts and Atlantic Storm Tracks Experiment (FASTEX). Eighty-seven conductivity-temperature-depth (CTD) stations were occupied along a four-section trapezoid, which spanned the "Northwest Corner" and the branching of the North Atlantic Current along 35 W. Realistic sea surface temperature analyses were produced every 15 days, using all available data collected in this area during the two months of the FASTEX experiment. These maps were combined with sea level anomaly fields from the TOPEX/Poseidon and ERS-2 satellites at the same time intervals to analyze the features of the main currents in the area and their evolution. These combined analyses, providing a coherent overview of the fronts and jets identified along the ship track, and the CTD stations are further used to estimate their transports. The general pattern is a 15 Sv (Sv Is equivalent to 10[sup 6] m[sup 3] s[sup -1]) transport by the North Atlantic Current at 47 N, 43 W, the existence of a recirculating gyre inside the Northwest Corner, and a complex branching of the circulation associated with significant surface fronts. The recirculating... [ABSTRACT FROM AUTHOR]

The Cape Cormorant Formation of the Table Head Group exposed on the Port au Port Peninsula, western Newfoundland, is composed of dark-brown to black shales with interbeds of thin calcareous silty and sandy distal turbidites. Distinctive carbonate conglomerates and breccias derived from the foundering shelf are occasionally found in the formation. The sediments accumulated in the foreland basin formed during the early stage of the Taconic orogeny. The faunas from the upper part of the Cape Cormorant Formation include graptolites, conodonts, and chitinozoans. The graptolites are well preserved, but are of low diversity and are referred to the Darriwil Pterograptus elegans Zone. Conodonts recorded from the distal turbidites are rare and fragmented. The faunas include taxa that are known from the St. George and Table Head groups. The conodont fauna is tentatively assigned to the Histiodella kristinae Phylozone and to the younger, unzoned interval. The chitinozoans are well preserved and the yield is high. The fauna is assigned to the Cyathochitina jenkinsi Zone and to an undefined interval. The abundance and diversity of the chitinozoan assemblages display a cyclic pattern, which is related to changes of the oceanic watermass in the foreland basin. The new chitinozoan species Belonechitina nevillensis n. sp., Belonechitina uniformipunctata n. sp., and Cyathochitina cormorani n. sp. are described.La Formation de Cape Cormorant du Groupe de Table Head affleurant dans la péninsule de Port au Port, dans l'ouest de Terre-Neuve, est composée de schistes argileux brun foncé à noirs avec de minces interlits de turbidites distales, calcareuses, silteuses et sablonneuses. Des brèches et des conglomérats à carbonate distinctifs et dérivés de la plate-forme en effondrement se retrouvent occasionnellement dans la formation. Les sédiments se sont accumulés dans le bassin d'avant-pays qui s'est formé au cours du premier stage de l'orogénie taconique. La faune de la partie supérieure de la Formation de Cape Cormorant comprend des Graptolites, des Conodontes et des Chitinozoaires. Les Graptolites sont bien conservés, mais faiblement diversifiés, et ils sont rattachés à la zone Pterograptus elegans de Darriwil. Les Conodontes provenant de turbidites distales sont rares et fragmentés. La faune comprend des taxons qui sont connus des groupes de St. George et de Table Head. La faune des Conodontes est provisoirement assignée à la phylozone Histiodella kristinae et à l'intervalle plus jeune qui n'est pas zoné. Les Chitinozoaires sont bien préservés et abondants. La faune est assignée à la zone Cyathochitina jenkinsi et à un intervalle indéfini. L'abondance et la diversité des assemblages de Chitinozoaires démontrent un patron cyclique qui est relié aux changements de la masse d'eau océanique dans le bassin d'avant-pays. On décrit les nouvelles espèces de Chitinozoaires Belonechitina nevillensis n. sp., Belonechitina uniformipunctata n.sp. et Cyathochitina cormorani n. sp. [ABSTRACT FROM AUTHOR]

Sediment cores from six small lake basins in the Canadian high Arctic reveal a gravel-rich (≤30% by weight) to gravel-poor (≥2%) diamict facies underlying massive, post-glacial, clayey silt. Ten other lakes contain a second diamict facies within what are interpreted to be glaciolacustrine sedimentary assemblages. The sedimentology, clast fabrics and fossil remains (diatoms, ostracodes and chironomid head capsules) within both diamict facies suggest that these deposits are not tills. Clast fabrics yielded low S1 (0·41–0·57) and high S3 (0·09–0·22) eigenvalues, placing them within the range of ice-rafted diamictons and glacigenic sediment flows. The high percentage of clast dip angles >45° (15–61%), random clast azimuth and lower diamict contacts conformable to underlying current-bedded sediment favours an origin as a rain-out or settling deposit. Samples of the matrix and scrapings of clasts from the diamicts revealed a diatom assemblage dominated by littoral and planktonic forms, such as are found in the littoral regions of the lakes today. This contrasts sharply with the assemblages within the overlying clayey silt, in which benthic forms predominate. Clasts are thus interpreted to have been rafted from the littoral areas of the lake. The process proposed to explain this is rafting by the lake ice cover in a glacial-marginal environment. Early season meltwater, impounded along the lateral margin of retreating cold-based glaciers, would buoyantly lift the lake ice cover and any adfrozen lake sediment. Higher lake levels and increased areal extent of seasonal freeze-on between the lake ice cover and the lake bed would allow the redeposition of littoral sediments to the benthic regions through greater lateral shifting of the ice cover as it broke up. Incision by meltwater streams into the lateral glacial margins would later isolate the lake, allowing seasonal warming of lake water, enough to support the growth and maturation of the ostracode and chironomid species found as fossils within the diamicts. [ABSTRACT FROM AUTHOR]

Presents a study which restored the post Taconian successor basin, the Gaspe Belt located within the external part of the Acadian orogen in the Canadian Appalachians. Overview on the attempts on reconstructing and restoring deformed parts of orogens or in tectonic regions; Deformation history of the belt; Steps toward the restoration of the basin; Discussion; Conclusions.

There are many geologic resource assessment techniques available that can be used to estimate the hydrocarbon potential of frontier basins. The techniques do not, however, produce discovery rate forecasts, which are critical to government and industry planners. Various methods of predicting the discovery rate in frontier basins are reviewed and appraised within the context of the drilling history of Canada's Scotian Shelf. The reviewed models include a mean historical discovery rate technique, the exponential decline model, a logistic curve technique and a class of models based on a sampling without replacement approach to prediction. Models are found to perform best over the longer forecast horizons, with those models based on the sampling without replacement technique tending to perform best. [ABSTRACT FROM AUTHOR]