Search

The Sandy Lake basin in northwestern Ontario is a potentially important area for insights into the late history of glacial Lake Agassiz because of its extensive glaciolacustrine deposits and well-preserved shoreline features of this geological episode. However, little information is available on its deglaciation history. Recent mapping shows the withdrawal of the ice from the basin center and subsequent deposition of extensive varved clay in the lake with an optically stimulated luminescence-dated maximum age at 11.4 ± 0.9 ka. With its further recession, the ice constructed the Opasquia moraine on the northern rim of the basin sometime before the development on the moraine of the first major shoreline of the lake (the The Pas, inferred at 10.1 ka). Lowering of the lake level formed many strandlines on the moraine and elsewhere in the basin, which can be correlated with those in the main Agassiz basin based on projected water planes (the The Pas to Ponton). Radiocarbon dating on basal wood remains of surface peat in a former strait defined by the Ponton shoreline and a nearby site on the former lake floor indicates the abandonment of this shoreline and hence the withdrawal of Lake Agassiz from the Sandy Lake basin by 8.3 ± 0.1 cal ka (UOC-7883). The date, although a minimum-limiting age, provides the hitherto best possible age constraint for the Ponton–Kinojévis shorelines, which many hypothesize represent one of the major lake levels during the final drainage of Lake Agassiz into Hudson Bay but have never been adequately dated before. [ABSTRACT FROM AUTHOR]

This paper quantifies rates of shoreline change and investigates the influence of surficial geology on shoreline dynamics between 1950 and 2018 on Pelly Island, located 10 km off the Mackenzie Delta. Long-term changes in shoreline position were calculated using imagery analysis and Analysing Moving Boundaries Using R (AMBUR). The influence of shoreline exposure to predominant storm direction and influence of surficial geology were examined for northwestern and southeastern zones. The average annual linear regression rate (LRR) rate during the 1950–2018 observation period was −3.8 m·a−1. The end point rate (EPR) was calculated for seven observation periods: 1950–1972, 1972–1985, 1985–2000, 2000–2018, 2000–2013, 2013–2018, and 1950–2018. A mean EPR of −5.5 ± 0.7 m·a−1 was calculated for the 2000–2018 period, and a maximum retreat rate of 46.7 ± 2.1 m·a−1 was recorded during the 2013–2018 observation period. By comparing the rate of change for sections of historical shorelines with differing surficial geology and exposure to storms, it was possible to draw conclusions on why Pelly Island continues to have the highest retreat rates in the Mackenzie–Beaufort region. Greater retreat rates were observed in lacustrine deposits (5.3 m·a−1) compared with moraine deposits (2.7 m·a−1). In addition, shoreline exposure to the predominant storm direction from the northwest was found to be a major influence on rates of shoreline change in all observation periods. [ABSTRACT FROM AUTHOR]

The glacial land system of western Keewatin region, northern Canada, consists of three significant events: (1) regional emplacement of subglacial sediments, mainly till; (2) landscape erosion with development of an integrated, anabranched network of meltwater drainage routes leading to meltwater corridors; and (3) deposition of an extensive array of eskers, and related landforms, within meltwater corridors. Integration of extensive field observations, mapping, and remotely sensed data allow us to link scoured bedrock and till surfaces, truncated drumlins, scour pits, glaciofluvial terraces, boulder lags, and a large-scale network of corridors, as part of regional meltwater erosion events. The network of long (∼100–200 km), relatively wide (∼1–3 km) meltwater corridors record confined subglacial erosion that scoured sediment (and bedrock) prior to glaciofluvial sedimentation (predominately eskers). Despite considerable sediment erosion along meltwater corridors, moraines and other ice-marginal deposits are rarely observed on the western Keewatin landscape. The absence of these features is inconsistent with deglacial models relying on step-wise active retreat of the ice margin. Instead, we propose that deglaciation of the western Keewatin sector of the Laurentide Ice Sheet was predominantly controlled by regional thinning and stagnation. These findings raise fundamental questions about deglacial patterns and processes and thus suggest that further evaluation and revision of existing models of deglacial chronology for this sector of the Laurentide Ice Sheet is needed. [ABSTRACT FROM AUTHOR]

Recent surges of Dań Zhùr (Donjek) Glacier have formed lakes at the glacier terminus that have drained catastrophically, resulting in hazards to people and infrastructure downstream. Here we use air photos and satellite imagery to describe lake formation, and the timing of filling and draining, since the 1930s. Between the 1930s and late 1980s, lakes were typically small (<0.6 km2), took many years to form after a surge event, and drained slowly as they were displaced by the glacier advancing in the next surge. However, since 1993, the lakes have become larger (>1 km2) and drain rapidly through or under the glacier by breaking a terminal ice dam. For the past two surges, since 2001, the lakes formed during or immediately after a surge in an increasingly larger basin between the Neoglacial maximum moraine and an increasingly smaller maximum terminus extent. Most recently, the 2012–2014 surge created a lake that drained in summer 2017, refilled, and drained again in both summer 2018 and summer 2019. The 2019 lake was 2.2 km2, the largest on record, and drained entirely within 2 days. While a lake is unlikely to form again before the next expected surge in the mid-2020s, future surges of Dań Zhùr Glacier are still likely to create terminal lakes, necessitating continued monitoring for surge activity and lake formation. [ABSTRACT FROM AUTHOR]

The hypothesis that Oak Ridges Moraine (ORM) formed between converging ice streams requires critical testing. Available data (e.g., digital elevation models, maps, seismic profiles, continuous cores, and pit exposures) are inconsistent with the converging ice stream hypothesis. Combined analysis of landform and subsurface data permits testing the ORM area stratigraphic sequence and sedimentary origin. Stratigraphic data indicate that drumlinized Newmarket Till, incised by north–south-oriented (tunnel) valleys, extends beneath ORM. Thus, streamlining on Newmarket Till is older than ORM and has no direct bearing on its formation. The north–south-trending valleys truncate streamlined Newmarket Till, extend to bedrock, have inset eskers, and occur beneath ORM. Hence, these valleys are older than ORM and have a subglacial rather than a proglacial origin. Overlying the mega-scale lineations and incised channels are topographically elevated (>300 m a.s.l.), ORM glaciofluvial–glaciolacustrine sequences. Its east to west paleoflow trend indicates an east–west-oriented hydraulic gradient, orthogonal to expected gradients of proposed north-south converging ice streams. The exclusive presence of ORM meltwater sediments, with rare deformation, is incompatible with a converging ice stream, deforming-bed hypothesis. Halton sediment grades upward from stratified sand (ORM) to interbedded diamicton and glaciolacustrine sediment, rather than deformation till. Halton sediment overlies ORM and consequently the proposed Halton ice streaming is younger than the moraine. Halton Till is present in few of the predicted ice stream areas, and where Halton Till is present, it has no mega-scale lineations. In sum, the weight of evidence unequivocally argues against a converging ice-stream process model for the ORM. [ABSTRACT FROM AUTHOR]

Subsurface geological models are often used to visualize and analyze the nature, geometry, and variability of geologic and hydrogeologic units in the context of groundwater resource studies. The development of three-dimensional (3D) subsurface geological models covering increasingly larger model domains has steadily increased in recent years, in step with the rapid development of computing technology and software, and the increasing need to understand and manage groundwater resources at the regional scale. The models are then used by decision makers to guide activities and policies related to source water protection, well field development, and industrial or agricultural water use. It is important to ensure that the modelling techniques and procedures are able to accurately delineate and characterize the heterogeneity of the various geological environments included within the regional model domain. The purpose of this study is to examine if 3D stratigraphic models covering complex Quaternary deposits can be improved by splitting the regional model into multiple submodels based on the degree of variability observed between surrounding data points and informed by expert geological knowledge of the geological-depositional framework. This is demonstrated using subsurface data from the Paris Moraine area near Guelph in southern Ontario. The variogram models produced for each submodel region were able to better characterize the data variability, resulting in a more geologically realistic interpolation of the entire model domain as demonstrated by the comparison of the model output with preexisting maps of surficial geology and bedrock topography as well as depositional models for these complex glacial environments. Importantly, comparison between model outputs reveals significant differences in the resulting subsurface stratigraphy, complexity, and variability, which would in turn impact groundwater flow model predictions. [ABSTRACT FROM AUTHOR]

An introduction is presented which discusses articles within the issue on topics including buried valleys, moraines and glaciolacustrine environments.

The advance and retreat of ice lobe margins of the Laurentide Ice Sheet formed moraines that are a prevalent feature throughout southwestern Ontario. In contrast to the well-studied stratified moraine complexes, recessional and end moraines have largely been ignored in the context of hydrogeological studies. Recent urban growth has led to development pressures on these moraines and a need to better understand their hydrogeology. This study presents data sets from the Paris Moraine near Guelph, Ontario, to examine its geomorphology, internal composition, and the corresponding hydraulic properties of these ice-marginal features. The moraine's geomorphic elements were mapped using high-resolution Global Positioning System transects, aerial photograph analysis, and ground truthing. Nine continuous sediment cores were recovered to determine the nature and distribution of subsurface sedimentary units and their relation to the regional stratigraphic framework. Cores were described in detail using standard sedimentological techniques, and significant sediment heterogeneity was observed in cross sections. Grain-size analyses of over 150 samples provide site-specific estimates of saturated hydraulic conductivity. In addition, saturated hydraulic conductivity was measured on 104 samples using the falling head permeameter method. This study found that different scales of sediment heterogeneity occur across the moraine and the associated till plain and outwash. In contrast, the hydraulic conductivity varies much less. It is expected that certain sedimentary units at specific depths will impact groundwater flow at the centimetre to hundreds of metres scale, which is significant in environmental site assessments or for understanding contaminant hydrogeological problems. [ABSTRACT FROM AUTHOR]

Regional-scale three-dimensional modelling of Quaternary sediments in the Orangeville Moraine area of southwestern Ontario has been completed as part of the Ontario Geological Survey groundwater initiative and provides an improved understanding of the glacial history and conceptual hydrostratigraphic framework for that region. Older (Marine Isotope Stage (MIS) 3-5) diamicton, glaciolacustrine, glaciofluvial, and rare nonglacial deposits forming regional aquitards and local aquifers are found in the northwestern part of the area. Catfish Creek Till, deposited during the Last Glacial Maximum (LGM) (MIS 2), forms a key aquitard and stratigraphic marker at depth. Diamicton, fine-textured glaciolacustrine sediments, and the gravel, sand, and silt conduit and subaqueous fan sediments that constitute the overlying Orangeville Moraine were deposited in an ice-walled lake formed between ice lobes during retreat from the LGM. Diamicton deposited during late-glacial ice margin fluctuations forms the upper aquitard unit and buries the edges of the moraine. The Orangeville Moraine is the largest aquifer in the area, and is partially confined by the upper tills. Thick fine-textured glaciolacustrine deposits, Catfish Creek Till, and older aquitards separate the moraine from bedrock aquifers across most of the area. Depending on hydraulic gradients, buried bedrock valleys with gravel and sand fills have the potential to recharge the bedrock aquifer. [ABSTRACT FROM AUTHOR]

Geomorphological mapping using detailed morphometric analyses of newly available high-resolution (5 m) digital elevation datasets across more than 9000 km2 of southern Ontario shows that the Greater Toronto Area and its immediate environs, Canada's largest urban area, is built across the former till beds of two fast-flowing ice streams (the newly named Simcoe Ice Stream (SIS) and the Halton Ice Stream (HIS)) within the last Laurentide Ice Sheet (LIS). These formed during regional deglaciation sometime around 13 000 years before present and are directly analogous to fast-flowing (>3 km year−1) ice streams in today's Antarctic and Greenland ice sheets. Their subglacial footprint in southern Ontario consists of flow sets of highly elongated and closely spaced flow-parallel till ridges up to 4 km in length and 100 m in width (megascale glacial lineations) that converge on the Oak Ridges Moraine (ORM) from the north (SIS) and south (HIS). ORM is southern Ontario's largest glacial landform extending from the Niagara Escarpment to Kingston over some 160 km and was deposited as a series of en echelon glaciolacustrine fan deltas in a complexly evolving glaciolacustrine depocenter trapped between the converging ice streams; meltwater channels cut into the bed of the Simcoe Ice Stream suggest that glaciofluvial sediment was primarily supplied from the north. The sedimentology of the ORM is comparable to 'morainal banks' at the margins of ice streams terminating in water; some 70 km3 of sediment accumulated very rapidly (>300 years?) reflecting the ability of ice streams to move very large fluxes of sediment, combined with trapping of sediment between SIS and HIS. To date, more than 117 paleo ice streams have been recognized in the LIS and this study confirms the presence of additional corridors of fast-flowing ice in its eastern Great Lakes sector. The ice stream paradigm provides a uniformitarian foundation for a comprehensive re-evaluation of much existing glacial geologic mapping and stratigraphic work in southern Ontario that hitherto stressed the role of catastrophic regional subglacial megaflooding in the formation of the ORM and many other landforms. This paper advocates complete remapping of the glacial landscapes of southern Ontario using an 'ice stream landsystem' approach to determine the full number of ice streams in the eastern Great Lake sector of the last ice sheet. [ABSTRACT FROM AUTHOR]

Frank Mackie Glacier repeatedly advanced across the Bowser River valley in northwestern British Columbia to impound Tide Lake during the Holocene. The most recent infilling of Tide Lake was associated with a late Little Ice Age glacier advance and ended around 1930 when the lake catastrophically drained. Over the last century Frank Mackie Glacier has retreated and down wasted to reveal multiple glaciogenic sedimentary units within the proximal faces of prominent lateral moraines. The units are separated by buried in-situ tree stumps and laterally contiguous wood mats deposited on paleosols. Dendroglaciological and radiocarbon dating of these wood remains show that Frank Mackie Glacier expanded into standing forests at 3710-3300, 2700-2200, 1700-1290, 900-500, and 250-100 cal. years BP. These advances coincide closely in time with the previously established Tide Lake glacier dam chronology and with the Holocene history of other glaciers in the Bowser River watershed. The findings emphasize the likelihood that most glaciers within northwestern British Columbia underwent substantial size and mass balance changes over the last 4000 years, and often spent hundreds of years in advanced positions before retreating. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The sedimentary record of Otokomi Lake, Glacier National Park, Montana, was studied to determine the age of an adjacent Crowfoot moraine. The presence of Mt. St. Helens Jy ash near the bottom of the longest percussion core limits drainage basin deglaciation to before 11 400 14C years before present (BP), although 14 100 BP is the estimated basal age of the core. Correlative shifts in loss on ignition, coarse (#x003E;1 mm) grain size, magnetic susceptibility, and X-ray gray-scale data at a depth of 185 cm are interpreted to be related to a sedimentary change in Otokomi Lake brought about by the deposition of the adjacent Crowfoot moraine. The estimated age of the moraine is 10 590 BP, which is within the Younger Dryas interval. This information supports the hypothesis that Crowfoot moraines represent a regional western North American response to Younger Dryas cooling. [ABSTRACT FROM AUTHOR]

Holocene lateral moraines in the Coast Mountains of British Columbia are commonly composed of multiple drift units related to several glacier advances. In this paper, we document lateral moraine stratigraphy at Lillooet Glacier in the southern Coast Mountains. Five tills, separated by laterally extensive paleosols and layers of large woody debris, were found in three cross-sectional exposures through the northeast lateral moraine and two shallow gullies incised into its steep proximal face. Eighteen new radiocarbon ages constrain the timing of five separate advances of Lillooet Glacier: (1) prior to 3000 14C years BP; (2) ~3000 14C years BP; (3) ~2500 14C years BP; (4) ~1700 to 1400 14C years BP; and (5) during the Little Ice Age (LIA), after 470 14C years BP. The Lillooet Glacier chronology is broadly synchronous with other glacier records from the Coast Mountains. These records collectively demonstrate climate variability at higher frequencies during the late Holocene than is apparent from many paleoecological reconstructions. Reconstructions of glacier fluctuations are often hampered by poor preservation of landforms that predate the extensive LIA advances of the latest Holocene. Our results highlight the potential of lateral moraine stratigraphy for reconstructing these earlier events. [ABSTRACT FROM AUTHOR]

Dendroglaciological and lichenometric techniques are used to establish the Little Ice Age (LIA) history of two glaciers (Colonel Foster and Septimus) in Strathcona Provincial Park, Vancouver Island, British Columbia. Our lichenometric investigations were preceded by the development of a locally calibrated Rhizocarpon geographicum growth curve (1708–1998 A.D.). Documentation of a 3–4-year ecesis interval for both trees and lichen greatly reduces one of the main uncertainties in using geobotanical methods for dating LIA landforms. The moraine dates provided, therefore, give a good approximation of the shift in climate conditions that lead to the retreat of the glaciers and subsequent moraine stabilization. Geobotanical evidence records three synchronous episodes of LIA moraine deposition at both glaciers: two prominent moraines at each site are dated to the early 1700s and late 1800s, with a third, smaller moraine dated to the mid 1930s. Moraines deposited prior to 1397 A.D. were also recorded at Colonel Foster Glacier; however, precise dating of these moraines was not possible. The moraine records from Strathcona Provincial Park suggest two possible modes of glacier response: (i) synchronous responses to larger-scale climatic forcing, and (ii) asynchronous responses to local factors such as microclimate, topography, and glacier geometry. The Vancouver Island LIA record was evaluated in the context of LIA results from the Pacific North American (PNA) Cordillera. It compares well with regional moraine records from coastal British Columbia, Washington, Alaska, and the Canadian Rocky Mountains, suggesting a regional response of PNA glaciers to climate change associated with the LIA. [ABSTRACT FROM AUTHOR]

New geomorphic data from the Lake Terrell uplands along the western margin of the Fraser Lowland in Washington reveal moraines (and (or) a complex grounding zone) and raised marine terraces. A large ridge that almost encircles the upland is asymmetric, and its surface material consists of fine- to coarse-grained diamictons. These ridges are argued to have formed adjacent to an ice margin near the marine limit, where the depositional processes are variable (e.g., ice-rafted rainout, dumping, sediment gravity flow). Multiple crests and crosscutting relations suggest that at least two glacial resurgences occurred during deglaciation of this area. The presence of these features, and their probable extent and stratigraphic position, raise several questions about relative sea-level history and ice margin reconstructions for this area. [ABSTRACT FROM AUTHOR]

The establishment of fourteen Little Ice Age (LIA) glacier chronologies in the Mt. Waddington area led to the development of an extended history of glacial activity in this portion of the southern British Columbia Coast Mountains, Canada. The glaciers were located within four different mountain ranges, and were of varying size and aspect. Dendrochronological and lichenometric techniques were used to provide relative age estimates of moraines formed as glacier termini retreated from advanced positions. Evidence for pre-LIA glacial events is best preserved at Tiedemann Glacier, where the oldest glacial advances date to A.D. 620 and 925–933. Soil-covered and well-vegetated moraines built at Cathedral, Pagoda, and Siva glaciers date to between A.D. 1203 and 1226. Following this event, moraines constructed at Ragnarok, Siva, and Cathedral glaciers in the mid-14th century suggest glaciers in the region underwent a period of downwasting and retreat before readvancing. The majority of moraines recorded in the Mt. Waddington area describe late-LIA glacial events shown to have constructed moraines that date to A.D. 1443–1458, 1506–1524, 1562–1575, 1597–1621, 1657–1660, 1767–1784, 1821–1837, 1871–1900, 1915–1928, and 1942–1946. Over the last 500 years, these moraine-building episodes were shown to occur on average every 65 years and suggest there has been prolonged synchronicity in the glaciological response to persistent climate-forcing mechanisms. Nevertheless, our analysis suggests that local factors, such as aspect and size, play an important role in individual glacial response. Notably, ice termini of medium-size glaciers facing eastwards showed a quicker response to climatically induced mass balance changes. [ABSTRACT FROM AUTHOR]

New geomorphic, paleolimnological, and radiocarbon data suggest that a terminal moraine complex in the Northern Ogilvie Mountains, Yukon Territory, Canada, may represent the McConnell Glaciation (Late Wisconsinan), rather than the Reid Glaciation (marine isotope Stage 8; Illinoian) as previously thought. Relict fluvial channels on the surface of the moraine and analysis of a suite of lake sediment cores from Chapman Lake, a closed-basin kettle on the surface of the moraine, suggest that flow from the Blackstone River passed over the moraine and through the lake until ca. 12 500 BP, at which time the Blackstone River was captured by the East Blackstone River, diverting flow from the lake. Subsequent incision by the Blackstone River has left its base level more than 10 m below the level of Chapman Lake. Perched former outlets from Chapman Lake indicate that this incision must postdate stream capture. Because the Chapman Lake moraine is a topographic barrier across the Blackstone River valley, incision must have occurred shortly after deposition of the moraine, suggesting that the landscape surrounding Chapman Lake is substantially younger than previously thought. Additional radiocarbon dates also suggest that kettle subsidence at Chapman Lake was ongoing during the early Holocene and that North Fork Pass moraine, 15 km upvalley from the Chapman Lake moraine, may have been formed during the Late Glacial rather than the McConnell Glaciation.Selon de nouvelles données géomorphologiques, paléolimnologiques et de datation au radiocarbone, un complexe de moraine terminale dans les monts Ogilvie septentrionaux, Territoire du Yukon, Canada, pourrait représenter la glaciation McConnell (Wisconsinien tardif) plutôt que la glaciation Reid (isotope marin du stade 8, Illinoien) comme on le croyait antérieurement. Selon des anciens chenaux fluviaux à la surface de la moraine et l'analyse d'un ensemble de carottes de sédiments de lac provenant du lac Chapman, un bassin de marmite à la surface de la moraine, la rivière Blackstone aurait coulé sur la moraine et à travers le lac jusqu'à environ 12 500 BP, alors qu'elle a été capturée par la rivière Blackstone Est, déviant ainsi l'écoulement loin du lac. Une incision subséquente par la rivière Blackstone a laissé son niveau de base à plus de 10 m sous le niveau du lac Chapman. D'anciens exutoires perchés du lac Chapman indiquent que cette incision doit être postérieure à la capture de la rivière. Puisque la moraine du lac Chapman constitue une barrière topographique en travers de la vallée de la rivière Blackstone, l'incision a dû se produire peu de temps après la déposition de la moraine, suggérant que le paysage autour du lac Chapman soit substantiellement plus jeune qu'on ne l'aurait crû antérieurement. D'autres dates obtenues par radiocarbone suggèrent aussi que la subsidence des marmites au lac Chapman ait eu lieu tout au cours de l'Holocène précoce et que la moraine de North Fork Pass, située à 15 km en amont de la moraine du lac Chapman, pourrait avoir été formée au cours du tardiglaciaire plutôt qu'au cours de la glaciation McConnell.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The Holocene and late glacial history of fluctuations of Stutfield Glacier are reconstructed using moraine stratigraphy, tephrochronology, and dendroglaciology. Stratigraphic sections in the lateral moraines contain tills from at least three glacier advances separated by volcanic tephras and paleosols. The oldest, pre-Mazama till is correlated with the Crowfoot Advance (dated elsewhere to be Younger Dryas equivalent). A Neoglacial till is found between the Mazama tephra and a paleosol developed on the Bridge River tephra. A log dating 2400 BP from the upper part of this till indicates that this glacier advance, correlated with the Peyto Advance, culminated shortly before deposition of the Bridge River tephra. Radiocarbon and tree-ring dates from overridden trees exposed in moraine sections indicate that the initial Cavell (Little Ice Age (LIA)) Advance overrode this paleosol and trees after A.D. 1271. Three subsequent phases of the Cavell Advance were dated by dendrochronology. The maximum glacier extent occurred in the mid-18th century, predating 1743 on the southern lateral, although ice still occupied and tilted a tree on the north lateral in 1758. Subsequent glacier advances occurred ca. 1800–1816 and in the late 19th century. The relative extent of the LIA advances at Stutfield differs from that of other major eastward flowing outlets of the Columbia Icefield, which have maxima in the mid–late 19th century. This is the first study from the Canadian Rockies to demonstrate that the large, morphologically simple, lateral moraines defining the LIA glacier limits are actually composite features, built up progressively (but discontinuously) over the Holocene and contain evidence of multiple Holocene- and Crowfoot-age glacier advances.La stratigraphie des moraines, la téphrochronologie et la dendroglaciologie des moraines ont servi à reconstruire les fluctuations à l'Holocène et au cours de l'histoire glaciaire tardive du glacier Stutfield. Les sections stratigraphiques dans les moraines latérales contiennent des tills d'au moins trois avancées glaciaires séparées par des tephras volcaniques et des paléosols. Le plus ancien, le till pré-Mazama, est corrélé à l'avancée Crowfoot (dont on a déterminé l'âge ailleurs comme étant un équivalent du Dryas récent). Un till de l'époque néo-glaciaire se retrouve entre le tephra Mazama et un paléosol développé sur le tephra de Bridge River. Un billot, daté 2400 BP, provenant de la partie supérieure de ce till, indique que cette avancée glaciaire, corrélée à l'avancée de Peyto, a culminé peu de temps avant la déposition du tephra de Bridge River. Des datations au [sup 14] C et des séries chronlogiques provenant d'arbres recouverts, puis exposés dans des sections de moraine, indiquent que l'avancée Cavell initiale (petit âge glaciaire) a chevauché ce paléosol et les arbres après l'an 1271. La dendrochronologie a permis la datation de trois phases subséquentes de l'avancée Cavell. L'étendue glaciaire maximale eut lieu au milieu du 18e siècle, avant 1743 sur le coté sud bien que la glace fut encore présente sur le côté nord et y ait basculé un arbre en 1758. Des avancées glaciaires subséquentes ont eu lieu vers 1800-1816 et vers la fin du 19e siècle. L'étendue relative des avancées du petit âge glaciaire à Stutfield diffère de celles d'autres glaciers majeurs du champ de glace Columbia s'écoulant vers l'est et qui ont eu leur maximum dans la deuxième moitié du 19e siècle. Cette étude est la première provenant des Rocheuses canadiennes à démonter que les grandes moraines latérales morphologiquement simples définissant les limites du glacier au petit âge glaciaire sont en fait des éléments composites, développés progressivement (mais de façon discontinue) tout au cours de l'Holocène et qu'elles contiennent des évidences d'avancées glaciaires multiples d'âge Holocène et Crowfoot.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Discusses the implications for paleoclimate and for formation of hummocky moraine of the major end moraines of Younger Dryas age on Wollaston Peninsula, Victoria Island and the Canadian Arctic. Analysis of ice-cored topography; Details on the till layers forming the cap of the ice-cored moraines on the Tuktoyaktuk Peninsula; Evidence that shows ice-cored moraines would become classical hummocky moraine.