A study of the felt need of parents for parent education in child care, which might be met by a hospital program

Thesis (M.S.)--Boston Universit

Evidence from Keewatin (Central Nunavut) for Paleo-Ice Divide Migration

Ice directional indicators were compiled from extensive field mapping and air-photo interpretation in the Keewatin region of central Nunavut. The profusion of multi-faceted bedrock outcrops, intersecting striations, superimposed streamlined landforms, and stacked till units, particularly beneath the former Keewatin Ice Divide, is interpreted to be the result of the migration of the main ice divide in the region, by as much as 500 km between ice-flow phases, possibly through much of the Wisconsinan glaciation. This palimpsest glacial landscape reflects protection under an ice divide because of low-velocity basal sliding, and changes in flow velocity as a result of shifting ice flow centres. Relative ages of regional ice-flow sets were used to reconstruct multiple phases of paleo-ice flows, stemming from ice centres external to the region prior to or at LGM, and from a local ice divide throughout deglaciation. This work refutes previous interpretations of the age and stability of the Keewatin Ice Divide, and has implications for interpreting glacial dispersal trains and for mineral exploration in Keewatin.Des indices d’écoulement glaciaire ont été compilés à partir d’une cartographie à grande échelle sur le terrain et à l’aide de la photo-interprétation dans la région du Keewatin au centre du Nunavut. L’abondance d’affleurements rocheux à facettes multiples, de stries entrecroisées, de formes profilées superposées et d’unités de till empilées, notamment sous l’ancienne ligne de partage glaciaire du Keewatin, est le résultat de la migration de la ligne de partage glaciaire principale sur 500 km dans la région du Keewatin au cours de la glaciation du Wisconsinien. Ce paysage glaciaire est le vestige d’un glissement minimal sous la ligne de partage glaciaire et des variations de vitesse d’écoulement causées par le déplacement des centres d’écoulement. Les âges relatifs des familles d’écoulement glaciaire ont permis de reconstituer de nombreuses phases glaciaires anciennes, qui sont affectées par les centres d’écoulement situés à l’extérieur de la région et par une ligne de partage glaciaire locale jusqu'à la déglaciation. Ces résultats réfutent les interprétations antérieures quant à l’âge et à la stabilité de la ligne de partage glaciaire du Keewatin et ils aident à mieux comprendre les trains de dispersion glaciaire et l’exploration minérale dans la région du Keewatin

A quasi-annual record of time-transgressive esker formation: implications for ice sheet reconstruction and subglacial hydrology

We identify and map chains of esker beads (series of aligned mounds) up to 15 m high and on average ~ 65 m wide across central Nunavut, Canada from the high-resolution (2 m) ArcticDEM. Based on the close one-to-one association with regularly spaced, sharp crested ridges interpreted as De Geer moraines, we interpret the esker beads to be quasi-annual ice-marginal deposits formed time-transgressively at the mouth of subglacial conduits during deglaciation. Esker beads therefore preserve a high-resolution record of ice-margin retreat and subglacial hydrology. The well-organised beaded esker network implies that subglacial channelised drainage was relatively fixed in space and through time. Downstream esker bead spacing constrains the typical pace of deglaciation in central Nunavut between 7.2 and 6 ka 14C BP to 165–370 m yr−1, although with short periods of more rapid retreat (> 400 m yr−1). Under our time-transgressive interpretation, the lateral spacing of the observed eskers provides a true measure of subglacial conduit spacing for testing mathematical models of subglacial hydrology. Esker beads also record the volume of sediment deposited in each melt season, thus providing a minimum bound on annual sediment fluxes, which is in the range of 103–104 m3 yr−1 in each 6–10 km wide subglacial conduit catchment. We suggest the prevalence of esker beads across this predominantly marine terminating sector of the former Laurentide Ice Sheet is a result of sediment fluxes that were unable to backfill conduits at a rate faster than ice-margin retreat. Esker ridges, conversely, are hypothesised to form when sediment backfilling of the subglacial conduit outpaced retreat resulting in headward esker growth close to but behind the margin. The implication, in accordance with recent modelling results, is that eskers in general record a composite signature of ice-marginal drainage rather than a temporal snapshot of ice-sheet wide subglacial drainage

Conceptual model for the formation of bedforms along subglacial meltwater corridors (SMCs) by variable ice‐water‐bed interactions

Subglacial meltwater landforms found on palaeo-ice sheet beds allow the properties of meltwater drainage to be reconstructed, informing our understanding of modern-day subglacial hydrological processes. In northern Canada and Fennoscandia, subglacial meltwater landforms are largely organized into continental-scale networks of subglacial meltwater corridors (SMCs), interpreted as the relics of subglacial drainage systems undergoing variations in meltwater input, effective pressure and drainage efficiency. We review the current state of knowledge of bedforms (hummocks, ridges, murtoos, ribbed bedforms) and associated landforms (channels, eskers) described along SMCs and use selected high-resolution DEMs in Canada and Fennoscandia to complete the bedform catalogue and categorize their characteristics, patterning and spatial distributions. We synthesize the diversity of bedform and formation processes occurring along subglacial drainage routes in a conceptual model invoking spatiotemporal changes in hydraulic connectivity, basal meltwater pressure and ice-bed coupling, which influences the evolution of subglacial processes (bed deformation, erosion, deposition) along subglacial drainage systems. When the hydraulic capacity of the subglacial drainage system is overwhelmed glaciofluvial erosion and deposition will dominate in the SMC, resulting in tracts of hummocks and ridges arising from both fragmentation of underlying pre-existing bedforms and downstream deposition of sediments in basal cavities and crevasses. Re-coupling of ice with the bed, when meltwater supply decreases, facilitates deformation, transforming existing and producing new bedforms concomitant with the wider subglacial bedform imprint. We finally establish a range of future research perspectives to improve understanding of subglacial hydrology, geomorphic processes and bedform diversity along SMCs. These perspectives include the new acquisition of remote-sensing and field-based sedimentological and geomorphological data, a better connection between the interpreted subglacial drainage configurations down corridors and the mathematical treatments studying their stability, and the quantification of the scaling, distribution and evolution of the hydraulically connected drainage system beneath present-day ice masses to test our bedform-related conceptual model

La Moraine du Lac Bluenose (Territoires du Nord-Ouest), une moraine à noyau de glace de glacier

South of Dolphin and Union Strait, N.W.T., massive ridges of bouldery till, up to 100 m high, delimit an ice frontal position to the east and north of Bluenose Lake. Major ridges are either massive or composite with linear longitudinal pattern on their crest. Up ice (east from the ridges the most common landforms are boulder-covered hills, up to 60 m high, and hummocks interspersed with numerous lakes. In a well exposed section, sediment-rich ice is overlain by a bouldery till, more than 3 m thick, with a sandy to sandy silt matrix, columnar jointing and prismatic fissility. The icy sediments exhibit banding, folding and complex deformations, and include numerous boulders, cobbles, and pebbles. The upper contact of the icy sediments and the bouldery diamicton is sharp, subhorizontal and unconformable. These massive icy sediments are interpreted as basal glacier ice buried by the stacking of glacigenic debris, mostly till, carried at the base of a thrust-sheet in an area of compressive flow. This occurred in the ice frontal zone of an active Late Wisconsinan ice mass. It is postulated that if the regional climate was to warm to the point of melting the icy sediments which form the bulk of the Bluenose Lake Moraine the resulting landscape would be hummocky terrain similar to that which covers extensive regions in more southerly parts of Central Canada.Au sud du détroit du Dolphin et de l'Union, dans les Territoires du Nord-Ouest, des crêtes morainiques hautes de 100 m, composées de till à gros blocs marquent l'emplacement d'un front glaciaire à l'est et au nord du lac Bluenose. Les principales crêtes sont soit massives, soit composites avec de petites crêtes secondaires à leur sommet. En amont glaciaire (est) des crêtes, les formes de relief les plus fréquentes sont des collines recouvertes de blocs dont la hauteur atteint 60 m et des monticules entre lesquels se trouvent de nombreux lacs. Un important glissement de terrain au cœur de la moraine expose de la glace riche en sédiments, enfouie sous 3 m de till. Ce diamicton à matrice sabloneuse et riche en blocs exhibe une structure en colonnes et une fissilité prismatique. La glace enfouie qui incorpore des blocs et des cailloux est zonée, ce qui permet de déceler des plis et des déformations plus complexes. Le contact entre la glace enfouie et le diamicton est net, sub-horizontal et discordant. La glace est interprétée comme étant la partie basale d'un glacier enfouie par des sédiments glacigéniques, surtout du till. Dans une zone à écoulement à contre pente de la partie frontale de l'inlandsis du Wisconsinen supérieur des chevauchements ont transporté des sédiments qui ont recouvert la glace morte à la marge du front de glace active. Nous croyons que dans l'éventualité où un réchauffement climatique causerait la fonte de la glace enfouie, laquelle représente un volume important de la Moraine du Lac Bluenose, le relief serait transformé en un paysage bosselé semblable à celui qui existe dans des régions plus méridionales du Canada central

Till Geochemistry as a Vector to Metasomatic Iron and Alkali-Calcic Systems and Associated Deposits in the Great Bear Magmatic Zone, Northwest Territories, Canada

Recent advances in the characterization of metasomatic iron and alkali-calcic (MIAC) systems with associated iron-oxide apatite (IOA) prospects and iron-oxide–copper–gold (IOCG) and metasomatic cobalt deposits of the Great Bear magmatic zone were used to determine if the geochemistry of glacial sediments can unveil pathfinder elements indicative of mineralization and associated alteration. Analysis of variance within bedrock lithogeochemical (n = 707 samples) and till geochemical datasets (n = 92 samples) are compared. Results show that Fe, Co, Ni, Cu, As, Mo, Bi, La, Th, U, and W were identified as potential vectoring elements in different fractions of till due to their anomalous concentrations down-ice of various mineralized outcrops within the study area. For instance, Fe, Co, Cu, and Mo were established as the most useful vectoring elements in the locally derived till (<2 km down-ice) near the Sue Dianne IOCG deposit, and Fe, Co, Ni, Cu, Mo, W, Bi, and U near the Fab IOCG prospect. At the Sue Dianne deposit, the ratios of near-total (4-acid digestion) versus partial (modified aqua regia digestion) concentrations in the silt + clay-sized till fraction (<0.063 mm) for both La and Th reflect the mineralization alteration signature and define a more consistent dispersal train from mineralization compared to element concentrations mapped alone. Additional testing in an area of continuous till cover near an isolated point source is recommended to further develop the elemental ratio method for exploration of MIAC systems

Mapping Surficial Materials in Nunavut using RADARSAT-2 C-HH and C-HV, Landsat-8 OLI, DEM and Slope Data

The Canadian Arctic is currently subject to increased mapping activities for providing better knowledge to assist in making informed decisions for sustainable development. Surficial material maps are one of the required maps. For an area located in Nunavut, we produced a map with 21 surficial material classes by applying a non-parametric classifier, Random Forests (RF), to a combination of RADARSAT-2 C-HH and C-HV with Landsat-8 OLI, digital elevation model, and slope data. We also tested the All-polygon and Sub-polygon scripts of RF. Validation accuracies were determined by comparing the resulting maps to more than 1000 field sites. By adding RADARSAT-2 dual-polarized images, the classification overall accuracy increases from 90.6% to 96.4% with the Sub-polygon script and from 92.8% to 98.1% with the All-polygon script. The overall validation accuracy increases from 76.3% to 88.9% with the Sub-polygon script and from 76.4% to 93.3% with the All-polygon script. With the All-polygon script, the validation accuracies are above 85% for all classes, except the user’s accuracy of gravelly till (76.7%) and the producer’s accuracy of sand and gravel with vegetation (70%), both classes being confused with thin till over bedrock