Late Glacial landforms of Wollaston Peninsula, Victoria Island, Northwest Territories: product of ice-marginal retreat, surge, and mass stagnation

1988 ◽  
Vol 25 (2) ◽  
pp. 262-279 ◽  
Author(s):  
David R. Sharpe
Keyword(s):  
Northwest Territories ◽  
Large Scale ◽  
Regional Scale ◽  
Late Glacial ◽  
Ground Moraine ◽  
Ice Conditions ◽  
Late Wisconsinan ◽  
Victoria Island ◽  
Glacial Landforms ◽  
Subglacial Meltwater

An analysis of glacial landforms on a regional scale leads to an interpretation of the dynamics of Late Wisconsinan glaciation on Wollaston Peninsula, Victoria Island, Northwest Territories. The glacial record is dominated by four adjacent belts of landforms: (I) ground moraine (till plains and ice-marginal drainage features), (II) hummocky moraine, (III) lateral and shear moraine, and (IV) streamlined landforms. The landform belts are considered as representing four distinct glacial ice conditions or regimes: (1) ice-margin retreat during extending flow of thin, active ice; (2) marginal ice stagnation following compressional flow; (3) a surging ice margin producing massive shear moraines; and (4) large-scale flooding and mass ice stagnation following a surge. These landform belts were arranged in zones by topographically controlled glacial dynamics, the latter two defining a former ice stream.Glaciological inferences can be extended by examining the sediments and processes that produced each landform set. Ground-moraine sediments were produced mainly subglacially from melt out or lodgment of glacial debris. Hummocky moraine resulted from debris flow and meltwater deposition controlled by ice, from resedimentation by sediment gravity flow, and from slump. Compressional shearing stacked thick deposits of drift prior to resedimentation. Simple lateral or end moraines may comprise interbedded sediment gravity flows deposited at static ice margins. Deformed lateral moraines resulted from intense marginal compressive flow that sheared and stacked thick, coarse sediment ridges or plates. This lateral shearing may be attributed to streaming or large ice surges. Drumlin exposures showed undeformed, interbedded, stratified sediments that appear to have accumulated in a subglacial cavity; there is no deformation related to high subglacial stress. Subglacial meltwater floods may have followed glacier surge. The greatly extended and thinner ice mass produced by the surge melted in place as clean (debris-free) ice.

Ice-sheet dynamics and subglacial meltwater regime inferred from form and sedimentology of glaciofluvial systems: Victoria Island, District of Franklin, Northwest Territories

1993 ◽  
Vol 30 (5) ◽  
pp. 928-944 ◽  
Author(s):  
T. A. Brennand ◽  
D. R. Sharpe
Keyword(s):  
Northwest Territories ◽  
Depositional Environment ◽  
Ice Sheet ◽  
Drainage System ◽  
Complex Flow ◽  
Grounding Line ◽  
Ice Sheet Dynamics ◽  
Victoria Island ◽  
Subglacial Meltwater ◽  
Tunnel Channel

On Victoria Island, tunnel channels, eskers, and associated fans and extended deposits together constitute channelized glaciofluvial systems. Flutes and drumlinoid ridges, interpreted as residuals left by erosive, catastrophic, subglacial meltwater sheet flows, lie adjacent to these systems. One tunnel channel is described in detail. It exhibits deep scours, a discontinuous thalweg, sculpted margins, and flutes on the downflow side of one wall, features indicative of complex flow and possibly several flow events. The tunnel channel is interpreted as the product of erosion by catastrophic, subglacial meltwater flow in a combined ice – substrate (R/N) channel.Esker sediments and morphology are used to infer details of the depositional environment and meltwater regime. A continuous esker with fans and extended deposits records seasonally controlled discharge events through an R-channel. These features may also suggest a grounding-line environment, thin ice, and localized ice floatation events. Less well connected ridges also record seasonally controlled meltwater rhythms and were produced within a thinning and stagnating ice mass; the depositional environment may have been in a subglacial R-channel or an ice-walled reentrant.Differences in the drainage system associated with each glaciofluvial landform, and temporal disconnection between tunnel channel and esker formation, is also suggested by possible paleoflow reversals between inferred catastrophic and seasonally controlled drainage phases. Changes in ice-sheet profiles between events may have been responsible.

A 10,000 yr B.P. Extensive Ice Shelf over Viscount Melville Sound, Arctic Canada

1984 ◽  
Vol 22 (1) ◽  
pp. 18-30 ◽  
Author(s):  
Douglas A. Hodgson ◽  
Jean-Serge Vincent
Keyword(s):  
Sea Level ◽  
North Coast ◽  
Major Advance ◽  
Ice Shelf ◽  
The North ◽  
Minimum Age ◽  
Western Arctic ◽  
Late Wisconsinan ◽  
Victoria Island ◽  
Glacial Landforms

Late Wisconsinan age glacial landforms and deposits indicate that an ice shelf of at least 60,000 km2 flowed northwestward into Viscount Melville Sound, probably from the M'Clintock Dome of the Laurentide Ice Sheet. The ice shelf overlapped coastal areas and laid Winter Harbour Till up to 125 m above present sea level on the southern coast of Melville Island, to 135 m on Byam Martin Island, to possibly 90 m on the northeast tip of Banks Island, and to 150 m on the north coast of Victoria Island. The contemporary sea level was 50 to 100 m higher than present (it now rises eastward). A maximum age of 10,340 ± 150 yr B.P. for the till, and thus the ice-shelf advance, is provided by shells in marine sediments which underlie it, whereas a minimum age of 9880 ± 150 yr B.P. is provided by overlying shells that postdate the ice advance. The major advance of shelf ice into Viscount Melville Sound may be the result of the rapid disintegration of the M'Clintock Dome while the climate ameliorated in the western Arctic.

Regional unconformities and the sedimentary architecture of the Oak Ridges Moraine area, southern Ontario

2004 ◽  
Vol 41 (2) ◽  
pp. 183-198 ◽  
Author(s):  
David Sharpe ◽  
André Pugin ◽  
Susan Pullan ◽  
John Shaw
Keyword(s):  
New York ◽  
Regional Scale ◽  
Late Glacial ◽  
Coarse Grained ◽  
Supporting Evidence ◽  
Seismic Profiles ◽  
Oak Ridges Moraine ◽  
Stratigraphic Architecture ◽  
Sedimentary Architecture ◽  
Subglacial Meltwater

Seismic stratigraphy, geometry, and sediment facies within the Oak Ridges Moraine (ORM) area of Ontario record major structural elements and surfaces of the Quaternary sedimentary sequence. The derived stratigraphic architecture can be used to identify the key elements of a regional erosional surface, represented by an unconformity in the subsurface, and associated overlying channel sediments. The erosional surface – unconformity forms a distinct time datum in the Quaternary sequence, which provides an important aid to lithostratigraphic correlation. The architecture also gives improved understanding of the effects of erosion on the late-glacial landscape. The surfaces of erosional drumlins and intervening troughs, and the beds and banks of meltwater channels in the ORM area, define the regional unconformity, highlighted by seismic profiles linked to continuously cored boreholes. These features are attributed to regional-scale, subglacial meltwater flow events. The sculpted surfaces, which are analogous to water-eroded forms, the presence of boulder lags and coarse-grained deposits on the regional erosional surface, and the channels with undulating profiles provide the vital supporting evidence for a meltwater interpretation. The inter-regional extent of the unconformity is inferred from the coherence of regional paleoflows and the extent of drumlinized uplands, tunnel channels, and scoured bedrock terrain across ~75% of the landscape from the ORM area east and south to the Finger Lakes, New York. The implied magnitude of erosion suggests a pressing need for directed sedimentological study in those ocean basins that were probable depositional sites for flood deposits.

Anatomy of a large-scale braid-plain quartzarenite from the Neoproterozoic Shaler Group, Victoria Island, Northwest Territories, Canada

1992 ◽  
Vol 29 (12) ◽  
pp. 2537-2550 ◽  
Author(s):  
Robert H. Rainbird
Keyword(s):  
Northwest Territories ◽  
Large Scale ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Playa Lakes ◽  
Braided Stream ◽  
Large Channel ◽  
Victoria Island ◽  
Moderate Scale ◽  
Lake Deposits

The Neoproterozoic Kuujjua Formation is an up to 120 m thick, texturally submature quartzarenite typified by laterally persistent tabular planar cosets of simple and compound planar crossbedding, intercalated with rare, thin dolomitic siltstone lenses up to tens of kilometres wide. It is interpreted as the deposit of a big river, occupying a braid plain, at least 150 km wide, which flowed into the Amundsen Basin from the southeast. The dominant elements of this deposit are stacked tabular and laterally continuous compound crossbeds, interpreted as very large channel forms, which migrated mainly by lateral accretion of superposed small- to moderate-scale two-dimensional dunes. Simple planar crossbedding represents moderate to large two-dimensional periodic bedforms deposited in channels. Rare trough crossbedding represents three-dimensional dunes, which probably were deposited in narrow low-stage chutes that cut across the larger bedforms. Dolomitic siltstone lenses are interpreted as deposits of large flood basin playa lakes that were periodically rejuvenated by river floods. Unrestricted migration of the channels back and forth across the braid plain reworked many of the thin lake deposits and produced the observed multistoried sandstone sheet geometry. A prevailing arid climate is indicated by the occurrence of evaporite casts and pseudomorphs in the flood-basin deposits. The Kuujjua Formation shares features with deposits of the Brahmaputra River; however, there appear to be no modern analogues for the thick, large-scale braided-stream deposits that characterized many Proterozoic cratonic basins.

Large-scale effects of subglacial meltwater flow in the southern Slave Province, Northwest Territories, Canada

2000 ◽  
Vol 37 (1) ◽  
pp. 81-93 ◽  
Author(s):  
V N Rampton
Keyword(s):  
Northwest Territories ◽  
High Velocity ◽  
Large Scale ◽  
High Pressures ◽  
Scale Effects ◽  
Dispersal Patterns ◽  
Slave Province ◽  
Glaciofluvial Deposits ◽  
Gravel Bars ◽  
Subglacial Meltwater

Broad corridors in the southern Slave Province of the Northwest Territories are marked by meltwater-scoured bedrock, irregular and transverse gravel ridges, gravel bars, crag and tail features (tails formed of gravel), drumlins, boulder lags, potholes, plunge pools, meltwater-sculpted slopes (in some cases defining till plateaus), and eskers. Most of the above features can either be attributed to the subglacial erosion of till by high-velocity, turbulent meltwater under high pressures and (or) meltwater transport and deposition of the eroded material. Potholes, plunge pools, and meltwater-sculpted slopes developed in unconsolidated deposits have received little attention in the literature, although they are the equivalent of similar features in bedrock that have had their origin attributed to subglacial meltwater erosion. In the case of inverted plunge pools, eroded materials, including boulders, have been transported upwards by meltwater some tens of metres during their formation. Features and deposits owing their origin to subglacial meltwater can lead to complex dispersal patterns of minerals and metals contained within both till and glaciofluvial deposits.

scholarly journals Evidence for abundant subglacial meltwater beneath the paleo-ice sheet in Pine Island Bay, Antarctica

2003 ◽  
Vol 49 (164) ◽  
pp. 125-138 ◽  
Author(s):  
Ashley L. Lowe ◽  
John B. Anderson
Keyword(s):  
Large Scale ◽  
Ice Sheet ◽  
Drainage System ◽  
West Antarctic Ice Sheet ◽  
Sedimentary Deposits ◽  
West Antarctic ◽  
Crystalline Bedrock ◽  
Glacial Landforms ◽  
Subglacial Meltwater ◽  
Subglacial Drainage

AbstractMarine-geological and -geophysical data collected from the continental shelf in Pine Island Bay, Antarctica, reveal a complex paleo-subglacial drainage system controlled by bedrock topography and subglacial meltwater discharge. Significant amounts of freely flowing meltwater existed beneath former ice sheets in Pine Island Bay. Subglacial drainage is characterized by descriptions of glacial landforms imaged on the sea floor and sedimentary deposits collected in piston cores. Bedrock geology is characterized using seismic data. Large-scale landforms on the shelf include channels and cavities incised into impermeable crystalline bedrock. There is a transition from randomly oriented channels on the inner shelf to a dendritic pattern of elongate channels on the middle shelf. On the outer shelf, a change in basal conditions occurs where sedimentary deposits bury crystalline bedrock. No evidence for flowing meltwater exists on sedimentary substrates. Instead, meltwater formed at the ice–sediment contact was incorporated into the sediments, contributing to development of a deforming bed, which was sampled in piston cores. Characterization of subglacial meltwater processes that occurred in the past may aid in understanding the role meltwater plays in stability of the West Antarctic ice sheet today.

Glacial and volcanic geomorphology of the Chimborazo-Carihuairazo Massif, Ecuadorian Andes

1990 ◽  
Vol 81 (2) ◽  
pp. 91-116 ◽  
Author(s):  
Chalmers M. Clapperton
Keyword(s):  
Large Scale ◽  
Parental Magma ◽  
Late Glacial ◽  
Explosive Activity ◽  
Last Glaciation ◽  
High Silica ◽  
Glacier Reconstruction ◽  
The Mean ◽  
Glacial Landforms ◽  
Effusive Eruptions

ABSTRACTThe Chimborazo (6,310 m)–Carihuairazo (5,102 m) massif is one of the largest ice-capped central volcanic complexes in the northern Andes. Combined evidence from volcanic and glacial landforms and sediments suggests cyclical evolution during the Pleistocene. Effusive eruptions of mixed high-silica andesite (SiO2%wt c. 60) predominated and built the bulk of the edifice. Explosive activity developed as the parental magma evolved to dacite-rhyolite (SiO2%wt 64–74), culminating with cone collapse and large-scale debris avalanching. Post-collapse activity evolved from the production of high-silica andesite to terminate with monogenetic eruptions of basic andesite (SiO2%wt 54–56) from flank fissures. The last eruption occurred before 11,000 yBP.The interstratification of volcanic and glacial deposits shows that glaciers expanded and contracted several times during the later Pleistocene, while the volcanic edifices were evolving. Glaciers expanded to altitudinal limits of 3,400–3,600 m during the early last glaciation and reached similar limits sometime after 33,000 yBP; an intervening interstadial interval lasted for 10,000 y. By 20,000–18,000 yBP, glaciers receded slightly because of decreased precipitation, but later readvances culiminated at 12,000–10,000 yBP and during the last 5,000 y. Glacier reconstruction and estimation of former equilibrium line altitudes suggest that the mean annual temperatures during the full glacial, late-glacial and Neoglaciation intervals were lower than now by c. 5–6°C, 2–3°C and 1°C, respectively, but these may be underestimates because of the assumption that precipitation was constant.

scholarly journals Holocene vegetation, fire and land use dynamics at Lake Svityaz, an agriculturally marginal site in northwestern Ukraine

2021 ◽  
Author(s):  
Christoph Schwörer ◽  
Erika Gobet ◽  
Jacqueline F. N. van Leeuwen ◽  
Sarah Bögli ◽  
Rachel Imboden ◽  
...  
Keyword(s):  
Bronze Age ◽  
Human Impact ◽  
Central Europe ◽  
Large Scale ◽  
Mixed Forest ◽  
Fire Risk ◽  
Late Glacial ◽  
Future Climate Change ◽  
Agricultural Activity ◽  
Fire Dynamics

AbstractObserving natural vegetation dynamics over the entire Holocene is difficult in Central Europe, due to pervasive and increasing human disturbance since the Neolithic. One strategy to minimize this limitation is to select a study site in an area that is marginal for agricultural activity. Here, we present a new sediment record from Lake Svityaz in northwestern Ukraine. We have reconstructed regional and local vegetation and fire dynamics since the Late Glacial using pollen, spores, macrofossils and charcoal. Boreal forest composed of Pinus sylvestris and Betula with continental Larix decidua and Pinus cembra established in the region around 13,450 cal bp, replacing an open, steppic landscape. The first temperate tree to expand was Ulmus at 11,800 cal bp, followed by Quercus, Fraxinus excelsior, Tilia and Corylus ca. 1,000 years later. Fire activity was highest during the Early Holocene, when summer solar insolation reached its maximum. Carpinus betulus and Fagus sylvatica established at ca. 6,000 cal bp, coinciding with the first indicators of agricultural activity in the region and a transient climatic shift to cooler and moister conditions. Human impact on the vegetation remained initially very low, only increasing during the Bronze Age, at ca. 3,400 cal bp. Large-scale forest openings and the establishment of the present-day cultural landscape occurred only during the past 500 years. The persistence of highly diverse mixed forest under absent or low anthropogenic disturbance until the Early Middle Ages corroborates the role of human impact in the impoverishment of temperate forests elsewhere in Central Europe. The preservation or reestablishment of such diverse forests may mitigate future climate change impacts, specifically by lowering fire risk under warmer and drier conditions.

scholarly journals Classification of Recreation Opportunity Spectrum Using Night Lights for Evidence of Humans and POI Data for Social Setting

2021 ◽  
Vol 13 (14) ◽  
pp. 7782
Author(s):  
Wenjing Zeng ◽  
Yongde Zhong ◽  
Dali Li ◽  
Jinyang Deng
Keyword(s):  
Large Scale ◽  
Regional Scale ◽  
Hunan Province ◽  
Social Settings ◽  
Recreation Opportunity Spectrum ◽  
City District ◽  
Night Lights ◽  
Recreational Resources ◽  
Metropolitan Counties ◽  
Land Types

The recreation opportunity spectrum (ROS) has been widely recognized as an effective tool for the inventory and planning of outdoor recreational resources. However, its applications have been primarily focused on forest-dominated settings with few studies being conducted on all land types at a regional scale. The creation of a ROS is based on physical, social, and managerial settings, with the physical setting being measured by three criteria: remoteness, size, and evidence of humans. One challenge to extending the ROS to all land types on a large scale is the difficulty of quantifying the evidence of humans and social settings. Thus, this study, for the first time, developed an innovative approach that used night lights as a proxy for evidence of humans and points of interest (POI) for social settings to generate an automatic ROS for Hunan Province using Geographic Information System (GIS) spatial analysis. The whole province was classified as primitive (2.51%), semi-primitive non-motorized (21.33%), semi-primitive motorized (38.60%), semi-developed natural (30.99%), developed natural (5.61%), and highly developed (0.96%), which was further divided into three subclasses: large-natural (0.63%), small natural (0.27%), and facilities (0.06%). In order to implement the management and utilization of natural recreational resources in Hunan Province at the county (city, district) level, the province’s 122 counties (cities, districts) were categorized into five levels based on the ROS factor dominance calculated at the county and provincial levels. These five levels include key natural recreational counties (cities, districts), general natural recreational counties (cities, districts), rural counties (cities, districts), general metropolitan counties (cities, districts), and key metropolitan counties (cities, districts), with the corresponding numbers being 8, 21, 50, 24, and 19, respectively.

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