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This paper examines particle settling dynamics in a tidally‐influenced delta, including observations of convective settling, strongly modulated by seasonal discharge and tidal cycles. Long time series of Acoustic Doppler Current Profiler backscatter, a proxy for suspended sediment concentration in the water column, current and sediment accumulation measurements from the slope of the Fraser River delta show variability of sedimentary processes over timescales from semi‐diurnal to annual. Acoustic Doppler Current Profiler backscatter shows a lagged response to river discharge and strong diurnal/semi‐diurnal variability. Most of the tidal cycle is characterized by a buoyant effluent plume. During the ebbing phase of diurnal major tides, discrete settling events are observed extending through the entire water column. The pulse‐like nature of these events is the result of downward plunging fingers characteristic of convective settling, similar to those observed in laboratory flume experiments, and appear to be initiated at the interface between the surface buoyant plume and the underlying ambient water. Currents show strong variability in a three‐layer water column. The surface plume shows offshore and southward directed transport of sediments. The remaining water column is influenced by tidal flows, but near surface and intermediate water‐depth currents are out of phase by several hours, indicating a stratification of the basin water and decoupled propagation of surface and internal tides. This phase lag is unlikely to cause discernible facies changes, but may have implications for basin‐fill patterns in restricted basins with strong tidal range. The results of this work will help to better understand river mouth sedimentation processes and dispersal patterns in other modern deltas and in the geological record. [ABSTRACT FROM AUTHOR]

Sediment waves are commonly observed on the sea floor and often vary in morphology and geometry according to factors such as seabed slope, density and discharge of turbidity currents, and the presence of persistent contour currents. This paper documents the morphology, internal geometry and distribution of deep‐water (4000 to 5000 m) bedforms observed on the sea floor offshore eastern Canada using high‐resolution multibeam bathymetry data and seismic stratigraphy. The bedforms have wavelengths of >1 km but fundamentally vary in terms of morphology and internal stratigraphy, and are distinguished into three main types. The first type, characterized by their long‐wavelength crescentic shape, is interpreted as net‐erosional cyclic steps. These cyclic steps were formed by turbidity currents flowing through canyons and overtopping and breaching levées. The second type, characterized by their linear shape and presence on levées, is interpreted as net‐depositional cyclic steps. These upslope migrating bedforms are strongly aggradational, indicating high sediment deposition from turbidity currents. The third type, characterized by their obliqueness to canyons, is observed on an open slope and is interpreted as antidunes. These antidunes were formed by the deflection of the upper dilute, low‐density parts of turbidity currents by contour currents. The modelling of the behaviour of these different types of turbidity currents reveals that fast‐flowing flows form cyclic steps while their upper parts overspill and are entrained westward by contour currents. The interaction between turbidity currents and contour currents results in flow thickening and reduced sediment concentration, which leads to lower flow velocities. Lower velocities, in turn, allow the formation of antidunes instead of cyclic steps because the densiometric Froude number (Fr′) decreases. Therefore, this study shows that both net‐erosional and net‐depositional cyclic steps are distributed along channels where turbidity currents prevail whereas antidunes form on open slopes, in a mixed turbidite/contourite system. This study provides insights into the influence of turbidity currents versus contour currents on the morphology, geometry and distribution of bedforms in a mixed turbidite–contourite system. [ABSTRACT FROM AUTHOR]

This paper analyzes short gravity cores sampled along transects in three adjacent deep fjord-lakes (lakes Pentecôte, Walker, and Pasteur) on the Québec North Shore, eastern Canada, to evaluate the distribution of laminated sediments and potential for varve formation. Facies analysis based on lithological description, digital photos, CT-scan images, and bathymetric data allowed for the identification of four main sediment facies, namely laminated sediments, partially laminated sediments, bioturbated sediments, and massive sediments. Direct evidence that Lake Walker undergoes thermal stratification was monitored from 2014 to 2016. Mean sedimentation rates and sedimentation fluxes of postglacial sediments in the distal basin of the three studied lakes are ≤0.12 cm a−1 and 0.03-0.16 g cm−2 a−1, respectively, based on 210Pb, 137Cs, and AMS radiocarbon dating. On the basis of thin section image analysis and 210Pb (CIC) chronology model, Lake Pentecôte contains mainly massive, partially laminated sediments, while Lake Pasteur contains partially laminated sediments and non-annual varve-like sediments. However, Lake Walker contains laminated sediments that are likely varves. The increased potential for laminae preservation observed in Lake Walker compared to lakes Pentecôte and Pasteur is associated with more favourable morphological characteristics including higher relative depth, mean depth, maximum depth, and topographic exposure. [ABSTRACT FROM AUTHOR]

This paper documents element mobility patterns from a magnetite-group Iron Oxide Copper–Gold (IOCG) prospect in the Northwest Territories of Canada and explores implications for space–time chemical evolution of metasomatic systems hosting IOCG deposits. The Fab system, located in the Great Bear magmatic zone (GBMZ) of the Northwest Territories, Canada, contains numerous Fe–Cu–U showings associated with high temperature (HT) potassic–iron alteration overprinting extensive zones of sodic to HT calcic–iron alteration. Each hydrothermal alteration assemblage is associated with distinct element mobility patterns that record evolving physico-chemical properties of the hydrothermal fluids. New geochronological data constrain the alteration and IOCG mineralization in the Fab system to a 3 m.y. window between 1870–1867 Ma, which is broadly contemporaneous with extensive high-level intrusive activity across the GBMZ. Regional- to local-scale element mobility patterns characteristic of the sodic and sodic–calcic–iron alteration type record leaching combined with weak to strong mass losses. Pure sodic alteration depleted the rocks in Ca, Co, Cu, Fe, Mg, Th, U and V. Conversely, sodic–calcic–iron alteration records significant depletions of Nb, REE, Ta, Ti, Th and U. These element mobility patterns differ from intense HT calcic–iron alteration that is enriched in Ca, Co, F, Fe, Mg, Mn, Ni and V with modest enrichments to locally significant mineralization in Th, U and REE. HT calcic–iron alteration is also characterized by substantial mass gains that translate into volume gains in stockwork zones and mass/volume gains in zones of intense host rock replacement. HT potassic–iron alteration is characterized by enrichments in Ba, K, Ni, U and V, along with locally Co and Cu. The temporal and spatial association of the Fab system alteration and the emplacement of the porphyritic dacite are indicative of the predominant involvement of magmatic–hydrothermal fluids. The high F- and Cl- contents of the porphyritic dacite and of the HT calcic–iron alteration zones as well as Nb, REE, Ta, Th, and Ti mobility provide strong evidences of high halogen activities (F and Cl) in the hydrothermal fluids. High F- and Cl-activities in the hydrothermal fluid are interpreted to have facilitated the mobilization of normally immobile (Nb, Ta, Ti, Th) or weakly mobile elements as well as some metals (e.g., V, Ni, Co). The formation of REE fluorocarbonates and calcite in the early and incipient HT calcic–iron alteration zones indicates the presence of CO 2 in the hydrothermal fluids. Weaker HFSE, HREE and Ti mobility during later HT potassic–iron alteration is interpreted to reflect decreasing temperatures, pressures, F-activities and increasing f O 2 as the fluids evolved and interacted with the host rocks. [ABSTRACT FROM AUTHOR]

Presents reply to the criticism of the research paper related to sediment intrusion and rheoplasis in Pennsylvanian fluvial strata of eastern Canada, prepared by the author, as of February 1989. Evaluation of the hypothesis of researchers H.W. van de Poll and I.M. Patel, regarding diapiric intrusion of siltstone into sandstone; Explanation regarding the visibility of two blocks of siltstones at Alma, Michigan; Reason for the absence of explanation of flutes and other structures in the research paper.

Discusses the research paper prepared by researcher A.G. Plint, regarding the concept of sediment intrusion and rheoplasis, in Pennsylvanian fluvial strata of eastern Canada, as of February 1989. Criticism of Plint's description of occurrences of slump blocks of Alma, Michigan, in the paper; Omission of the fluted mangled mass of twisted mudstone and sandstone in the paper; Demonstration regarding the formation of mudblocks and flute moulds in this area.

Drumlins are enigmatic subglacial landforms that have been interpreted to form by a number of processes, including incremental accumulation of till, erosion of previously deposited sediment, catastrophic meltwater floods, and sediment deformation. However, relatively little is known about the controls on drumlin formation, such as spatially variable glacial processes or substrate characteristics, and how these controls may be identified from variations in drumlin morphology within a single drumlin field. This paper explores a computational method that allows identification of drumlins and extraction of their morphological characteristics from existing topographic digital data for a portion of the Peterborough drumlin field in Ontario, Canada. Spatial and non-spatial analysis of the form and distribution of drumlins across the study area identifies drumlin characteristics such as size, elongation ratio, symmetry and long axis orientation and shows that drumlins are not randomly distributed across the region and their form characteristics have distinct regional trends. Kernel density analysis is used to identify the regional trends in drumlin characteristics. Factors that appear to influence the form and distribution of drumlins in the study area include sediment thickness, length of time beneath the ice, ice velocity and direction of ice movement. The distribution of particularly well developed asymmetric and elongate drumlins coincides with the location of a broad bedrock low and is interpreted to identify the former location of a fast-flowing ice stream. [ABSTRACT FROM AUTHOR]

Abstract: It is the intent of this paper to explore a significant extent of an entire passive continental margin for hydrate occurrence to understand hydrate modes of occurrence, preferred geologic settings and estimate potential volumes of methane. The presence of gas hydrates offshore of eastern Canada has long been inferred from estimated stability zone calculations, but little physical evidence has been offered. An extensive set of 2-D and 3-D, single and multi-channel seismic reflection data comprising in excess of 140,000 line-km was analyzed. Bottom simulating reflections (BSR) were unequivocally identified at seven sites, ranging between 250 and 445 m below the seafloor and in water depths of 620–2850 m. The combined area of the BSRs is 9311 km2, which comprises a small proportion of the entire theoretical stability zone along the Canadian Atlantic margin (∼715,165 km2). The BSR within at least six of these sites lies in a sedimentary drift deposit or sediment wave field, indicating the likelihood of grain sorting and potential porosity and permeability (reservoir) development. Although there are a variety of conditions required to generate and recognize a BSR, one might assume that these sites offer the most potential for highest hydrate concentration and exploitation. Total hydrate in formation at the sites of recognized BSR’s is estimated at 17 to 190 × 109 m3 or 0.28 to 3.12 × 1013 m3 of methane gas at STP. Although it has been shown that hydrate can exist without a BSR, the results from this regional study argue that conservative estimates of the global reserve of hydrate along continental margins are necessary. [Copyright &y& Elsevier]

Abstract: Runoff from agricultural watersheds can carry a number of agricultural pollutants and pathogens; often associated with the sediment fraction. Deposition of this sediment can impact water quality and the ecology of the river, and the re-suspension of such sediment can become sources of contamination for reaches downstream. In this paper a modelling framework to predict sediment and associated microbial erosion, transport and deposition is proposed for the South Nation River, Ontario, Canada. The modelling framework is based on empirical relationships (deposition and re-suspension fluxes), derived from laboratory experiments in a rotating circular flume using sediment collected from the river bed. The bed shear stress governing the deposition and re-suspension processes in the stream was predicted using a one dimensional mobile boundary flow model called MOBED. Counts of live bacteria associated with the suspended and bed sediments were used in conjunction with measured suspended sediment concentration at an upstream section to allow for the estimation of sediment associated microbial erosion, transport and deposition within the modelled river reach. Results suggest that the South Nation River is dominated by deposition periods with erosion only occurring at flows above approximately 250 m3 s−1 (above this threshold, all sediment (suspended and eroded) with associated bacteria are transported through the modelled reach). As microbes are often associated with sediments, and can survive for extended periods of time, the river bed is shown to be a possible source of pathogenic organisms for erosion and transport downstream during large storm events. It is clear that, shear levels, bacteria concentrations and suspended sediment are interrelated requiring that these parameters be studied together in order to understand aquatic microbial dynamics. It is important that any management strategies and operational assessments for the protection of human and aquatic health incorporate the sediment compartments (suspended and bed sediment) and the energy dynamics within the system in order to better predict the concentration of indicator organism. [Copyright &y& Elsevier]

The Thompson Nickel Belt marks the boundary between the Archean Superior Province and the Trans-Hudson Orogen in Canada. It comprises Archean gneisses, and Paleoproterozoic rocks with metasediments and metavolcanites (Ospwagan Group) and intrusions. The gneisses are frequently migmatitic and host numerous pegmatites. The western belt boundary is a fault contact with the Kisseynew Domain of the Reindeer Zone. In the south, the transition zone between the belt and the Kisseynew Domain comprises granitoids and a detrital sequence (Grass River Group), part of which grades into turbidites in the Kisseynew Domain. The eastern belt boundary is a diffuse zone where the Archean east-west (E-W) structural trend changes into the north-northeast (NNE) trend of the belt. This paper presents U-Pb ages for granitoids and 207Pb/206Pb detrital zircon ages from the Ospwagan and Grass River groups. Ages and a comparison of events in the belt and in the eastern Reindeer Zone have major implications. The change from stable platform deposits to syn-tectonic filling and emplacement of mafic intrusions in the Ospwagan Group are attributed to the convergence between the Reindeer Zone and the Superior Province at 1891-1885 Ma. At ca. 1850 Ma, continuing convergence led to drowning of marginal basins of the Superior craton and to the development of a transpressive regime in the belt, the onset of which could be as old as ca. 1885 Ma. Metamorphic ages of 1818-1785 record closure of the Kisseynew basin and crustal thickening. Collision of the new continental block with the Superior Province was accommodated by transpression until 1750-1720 Ma. La ceinture de Thompson est située entre le Craton archéen du Supérieur et l'orogène paléoprotérozoïque du Trans-Hudson, au Canada. Elle comprend des gneiss archéens souvent migmatitiques, et des roches paléoprotéroïques, métasédiments et métavolcanites (Groupe Ospwagan), et intrusions. A l'ouest, une zone de faille marque le contact entre la ceinture et le domaine Kisseynew de la Zone de Reindeer. Vers le sud, cette zone de transition entre la ceinture et le domaine Kisseynew comprends des granitoïdes et une séquence détritique (Groupe Grass River), qui passe graduellement aux turbidites du domaine Kisseynew. Sur la bordure orientale de la ceinture, le grain structural E-W du Craton archéen se réoriente dans le grain NNE de la ceinture. Cet article présente des âges U-Pb pour différents granitoïdes et des âges 207Pb/206Pb pour les zircons détritiques des groupes Ospwagan et Grass River. Les âges et une comparaison des événements affectant la ceinture et l'est de la zone Reindeer ont des implications importantes. Dans le groupe Ospwagan, le passage de dépôts de type plate-forme à des dépôts syn-tectoniques, et l'intrusion de roches basiques, sont attribuées à la convergence entre la zone Reindeer et le Craton du Supérieur vers 1891-1885 Ma. Vers 1850 Ma, la convergence conduit à l'enfouissement des bassins de la marge du Craton et à un régime transpressif pouvant avoir débuté dès ca. 1885 Ma. La fermeture du bassin de Kisseynew et l'épaississement crustal sont enregistrés par des âges de métamorphisme entre 1818 et 1785 Ma. Le régime transpressif se poursuit jusqu'à ca. 1750-1720 Ma. [ABSTRACT FROM AUTHOR]

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]

Abstract: The global oceanographic impact of large volumes of freshwater entering the Arctic Ocean from North America during Laurentide Ice Sheet deglaciation is the subject of much discussion. The model of lateglacial runoff-forced changes in ocean thermohaline circulation (THC) is constrained in part due to a lack of detailed study of the relevant terrestrial glacial sedimentary and geomorphic record. This paper reports and interprets sedimentary facies that accumulated in the former glacial Lake Mackenzie, which formed a long (~600 km) and deep (max: 200 m) lateglacial basin ponded along the lower Mackenzie Valley in Canada''s Northwest Territories. This is a key study area because the lake was dammed between approximately 10,500 14C yr bp and 9100 14C yr bp when most of the runoff from glacial Lake Agassiz was routed northward through the Mackenzie Valley to the Arctic Ocean. Detailed outcrop descriptions and geomorphic mapping in the glacial Lake Mackenzie basin fails to identify a clear record of abrupt shortlived flood outbursts but a regionally extensive deposit of massive and laminated mud at least 55 m thick, records trapping of large volumes of suspended fine sediment. Recent work shows the importance of suspended sediment content in freshwater runoff in influencing THC; too much sediment and freshwater enters the ocean hyperpycnally with little effect on surface waters. The role of Lake Mackenzie may have been to trap suspended sediment that otherwise would have been released to the Arctic Ocean, thereby acting to increase the effect of freshwater runoff on thermohaline circulation. [Copyright &y& Elsevier]

An overview of cohesive sediment transport processes is given in this paper, and a mass-balance equation that is commonly used to treat cohesive sediment transport is reviewed. The equation highlights transport parameters and processes that are important for modelling the transport of cohesive sediment. The flocculation mechanism that distinguishes cohesive sediment from its noncohesive counterpart is elaborated using a laboratory study that was carried out in a rotating circular flume using sediments from Hay River, Northwest Territories, Canada. A mathematical model of flocculation suitable for predicting flocculation of sediment in rotating circular flumes is reviewed. Other cohesive sediment transport processes such as erosion and deposition processes at the sediment-water interface, entrapment of fines in gravel beds, consolidation, fluid mud, and fluidization due to wave action are reviewed. Additional challenges and knowledge gaps that exist in the area of cohesive sediment transport are identified. [ABSTRACT FROM AUTHOR]

The lower reaches of West Nose Creek have been subject to urbanization since the 1970s, leading to channel widening and excessive erosion. This paper discusses what would likely happen if urbanization were allowed to continue in the same manner. Comparisons are presented of the channel width and depth for both the upstream rural and downstream urbanizing reaches. Estimates of the evolution of the creek were generated by linking the dominant discharge to the entire shape and volume of the hydrograph that the creek is subjected to rather than solely considering peak discharges. Potential remedial measures and stormwater management philosophies are discussed in relationship to instream flow needs (IFNs) initiatives. lFNs are generally developed by relating the amount of suitable aquatic habitat to the quantity of flow. The emphasis has so far been on IFNs for large river systems. Unfortunately, none of the IFN approaches cover streams that are subject to significant urbanization. In urbanized streams the issue is not as much the impacts due to withdrawals but due to significantly increased runoff rates and volumes generated within the urban areas. Examples are provided how fisheries habitat is impacted by the changed hydrologic regime and changed stream morphology. [ABSTRACT FROM AUTHOR]

There are two unreconciled interpretations for the age and character of the boundary separating the Cambrian–Ordovician Potsdam and Beekmantown groups that underlie the Ottawa Embayment in eastern Ontario. These stratal groups consist of interior facies of the central Laurentian Platform. As exposed in the type section of the Nepean Formation (upper Potsdam Group), located in the City of Ottawa, the boundary was previously interpreted to be conformable and of Early Ordovician age. This intepretation was of enormous impact on subsequent regional geology compilations that showed a diachronous boundary across the platform interior. From recent subsurface analysis across eastern Ontario, the contact was interpreted to be disconformable, a sequence boundary separating Late Cambrian and Early Ordovician strata. This paper reexamines the type section. Lithologically, the group boundary should be repositioned downsection by ~1.5 m. The contact now lies coincident with a disconformity that has a paleorelief of < 10 cm. The proposed revision is geologically significant. Previous collections of Early Ordovician conodonts from the type section, used to define the age of what had been interpreted to be upper Potsdam strata, now fall entirely within the lower Beekmantown Group. Nepean (Potsdam) strata exposed in the type section remain undated. Regional correlation of the disconformity across the Laurentian platform suggests that Nepean strata at the type section are likely of Late Cambrian age. There now exists a regionally coherent separation of Cambrian and Ordovician sedimentation patterns in the Ottawa Embayment. [ABSTRACT FROM AUTHOR]

This paper describes depositional properties of the fine portion (D<0.075 mm) of the surficial bed sediments taken from the Upper St. Clair River. The experiments were conducted using the circular flume facility at the Canada Center for Inland Waters in Burlington, Canada. Tests were conducted under the same initial conditions, which involved mechanical mixing following the application of a very high shear stress that resulted in a solids suspension of 200 g/L. Deposition was allowed to occur under five different shear stresses. The deposition rate and the floc size were monitored using a laser based Malvern particle size analyzer. The results were used to estimate the settling velocity as a function of applied shear stress and lapsed time for the selected shear stress. [ABSTRACT FROM AUTHOR]