Postglacial emergence of Amund and Ellef Ringnes islands, Nunavut: implications for the northwest sector of the Innuitian Ice Sheet

2004 ◽  
Vol 41 (3) ◽  
pp. 271-283 ◽  
Author(s):  
Nigel Atkinson ◽  
John England
Keyword(s):  
Late Holocene ◽  
Ice Sheet ◽  
The Arctic ◽  
Ice Flow ◽  
Geological Evidence ◽  
Level Curves ◽  
Ice Load ◽  
Holocene Transgression ◽  
Flow Features ◽  
Late Wisconsinan

This paper presents relative sea-level curves from Amund and Ellef Ringnes islands, northwest Queen Elizabeth Islands. These curves are of exponential form and record continuous, ongoing Holocene emergence, although northwest Ellef Ringnes Island is experiencing a late Holocene transgression. Isobases drawn on postglacial shorelines rise southeastward towards an uplift centre in Norwegian Bay. These suggest the Ringnes Islands occupied the northwest radius of the Innuitian uplift, which is congruent with glacial geological evidence suggesting parts of the Ringnes Islands were covered by the Late Wisconsinan Innuitian Ice Sheet. The isobases provide a provisional reconstruction of glacioisostatic recovery within the northwest Innuitian uplift. Their pattern supports earlier reconstructions that maximum Late Wisconsinan ice thickness occurred across Norwegian Bay, marking the position of an ice divide, which is consistent with ice-flow features on Amund Ringnes Island. They record the diminishing thickness of the Innuitian Ice Sheet from Norwegian Bay to the Arctic Ocean. The absence of an isobase embayment across the Ringnes Islands suggests a relatively uniform ice load across both islands and Hassel and Massey sounds. Parallel isobases across Peary Channel indicate this ice load extended beyond Massey Sound, although their northward deflection suggests an increasing influence of the former Axel Heiberg Island ice load.

scholarly journals Objective Reconstructions of the Late Wisconsinan Laurentide Ice Sheet and the Significance of Deformable Beds

2007 ◽  
Vol 39 (3) ◽  
pp. 229-238 ◽  
Author(s):  
D. A. Fisher ◽  
N. Reeh ◽  
K. Langley
Keyword(s):  
Yield Stress ◽  
Flow Direction ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Hudson Bay ◽  
Ice Streams ◽  
Ice Flow ◽  
Surface Slopes ◽  
Late Wisconsinan

ABSTRACT A three dimensional steady state plastic ice model; the present surface topography (on a 50 km grid); a recent concensus of the Late Wisconsinan maximum margin (PREST, 1984); and a simple map of ice yield stress are used to model the Laurentide Ice Sheet. A multi-domed, asymmetric reconstruction is computed without prior assumptions about flow lines. The effects of possible deforming beds are modelled by using the very low yield stress values suggested by MATHEWS (1974). Because of low yield stress (deforming beds) the model generates thin ice on the Prairies, Great Lakes area and, in one case, over Hudson Bay. Introduction of low yield stress (deformabie) regions also produces low surface slopes and abrupt ice flow direction changes. In certain circumstances large ice streams are generated along the boundaries between normal yield stress (non-deformable beds) and low yield stress ice (deformabie beds). Computer models are discussed in reference to the geologically-based reconstructions of SHILTS (1980) and DYKE ef al. (1982).

Coalescence of late Wisconsinan Cordilleran and Laurentide ice sheets east of the Rocky Mountain Foothills in the Dawson Creek region, northeast British Columbia, Canada

2016 ◽  
Vol 85 (3) ◽  
pp. 409-429 ◽  
Author(s):  
Adrian Scott Hickin ◽  
Olav B. Lian ◽  
Victor M. Levson
Keyword(s):  
British Columbia ◽  
Flow Direction ◽  
Ice Sheet ◽  
Rocky Mountain ◽  
Ice Flow ◽  
Oxygen Isotope Stage ◽  
Digital Elevation ◽  
Late Wisconsinan ◽  
Cordilleran Ice Sheet ◽  
River Valleys

Geomorphic, stratigraphic and geochronological evidence from northeast British Columbia (Canada) indicates that, during the late Wisconsinan (approximately equivalent to marine oxygen isotope stage [MIS] 2), a major lobe of western-sourced ice coalesced with the northeastern-sourced Laurentide Ice Sheet (LIS). High-resolution digital elevation models reveal a continuous 75 km-long field of streamlined landforms that indicate the ice flow direction of a major northeast-flowing lobe of the Cordilleran Ice Sheet (CIS) or a montane glacier (>200 km wide) was deflected to a north-northwest trajectory as it coalesced with the retreating LIS. The streamlined landforms are composed of till containing clasts of eastern provenance that imply that the LIS reached its maximum extent before the western-sourced ice flow crossed the area. Since the LIS only reached this region in the late Wisconsinan, the CIS/montane ice responsible for the streamlined landforms must have occupied the area after the LIS withdrew. Stratigraphy from the Murray and Pine river valleys supports a late Wisconsinan age for the surface landforms and records two glacial events separated by a non-glacial interval that was dated to be of middle Wisconsinan (MIS 3) age.

Postglacial relative sea-level change, Port au Port area, west Newfoundland

1985 ◽  
Vol 22 (7) ◽  
pp. 1039-1047 ◽  
Author(s):  
I. A. Brookes ◽  
D. B. Scott ◽  
J. H. McAndrews
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
High Water ◽  
Relative Sea Level ◽  
Radiocarbon Dates ◽  
Ice Load ◽  
Bay Area ◽  
Port Area ◽  
Minimum Age ◽  
Late Wisconsinan

We first report pollen and foraminifera analyses and radiocarbon dates from two cores taken from salt-marsh deposits bordering Port au Port Bay, southwestern Newfoundland. Results show that relative sea level (RSL) stood at 2.8 m below present higher high-water level (HHWL) at 2770 ± 300 years BP and at −1.8 m at 2365 ± 175 years BP at the core sites. They permit calculation of a rate of late Holocene RSL change from western Newfoundland. We then report other available dates bearing on the earlier RSL record of this area.A date of 5800 ± 200 years BP fixes the age of minimum RSL in Port au Port Bay at 11–14 m below present. A date of 9350 ± 120 years BP from St. George's provides a minimum age for the passage of sea level below present there. A date of 12 600 ± 140 years BP from Stephenville fixes a sea level at 29 m above present, whereas one of 13 600 ± 110 years BP from Abrahams Cove dates the marine limit at 44 m. These geographically restricted data closely constrain a curve of postglacial RSL change in the Port au Port Bay – northern St. George's Bay area. The form of the curve supports a recent model predicting sea-level response to wastage of a limited late Wisconsinan ice load in the wider region.

scholarly journals Laurentide Ice-Flow Patterns: A Historical Review, and Implications of the Dispersal of Belcher Islands Erratics

2007 ◽  
Vol 44 (2) ◽  
pp. 113-136 ◽  
Author(s):  
Victor K. Prest
Keyword(s):  
Ice Sheet ◽  
Historical Review ◽  
Flow Patterns ◽  
The Arctic ◽  
Laurentide Ice Sheet ◽  
Complex Nature ◽  
Hudson Bay ◽  
Ice Flow ◽  
Flow Models ◽  
The North

ABSTRACTThis paper deals with the evolution of ideas concerning the configuration of flow patterns of the great inland ice sheets east of the Cordillera. The interpretations of overall extent of Laurentide ice have changed little in a century (except in the Arctic) but the manner of growth, centres of outflow, and ice-flow patterns, remain somewhat controversial. Present geological data however, clearly favour the notion of multiple centres of ice flow. The first map of the extent of the North American ice cover was published in 1881. A multi-domed concept of the ice sheet was illustrated in an 1894 sketch-map of radial flow from dispersal areas east and west of Hudson Bay. The first large format glacial map of North America was published in 1913. The binary concept of the ice sheet was in vogue until 1943 when a single centre in Hudson Bay was proposed, based on the westward growth of ice from Labrador/Québec. This Hudson dome concept persisted but was not illustrated until 1977. By this time it was evident from dispersal studies that the single dome concept was not viable. Dispersal studies clearly indicate long-continued westward ice flow from Québec into and across southern Hudson Bay, as well as eastward flow from Keewatin into the northern part of the bay. Computer-type modelling of the Laurentide ice sheet(s) further indicates their complex nature. The distribution of two indicator erratics from the Proterozoicage Belcher Island Fold Belt Group help constrain ice flow models. These erratics have been dispersed widely to the west, southwest and south by the Labrador Sector of more than one Laurentide ice sheet. They are abundant across the Paleozoic terrain of the Hudson-James Bay lowland, but decrease in abundance across the adjoining Archean upland. Similar erratics are common in northern Manitoba in the zone of confluence between Labrador and Keewatin Sector ice. Scattered occurences across the Prairies occur within the realm of south-flowing Keewatin ice. As these erratics are not known, and presumably not present, in Keewatin, they indicate redirection and deposition by Keewatin ice following one or more older advances of Labrador ice. The distribution of indicator erratics thus test our concepts of ice sheet growth.

Pollen Analysis of the 1973 Ice Core from Devon Island Glacier, Canada

1984 ◽  
Vol 22 (1) ◽  
pp. 68-76 ◽  
Author(s):  
John H. McAndrews
Keyword(s):  
Late Holocene ◽  
Ice Core ◽  
Ice Sheet ◽  
Early Holocene ◽  
The Arctic ◽  
Devon Island ◽  
Glacier Ice ◽  
Shrub Tundra ◽  
Low Arctic ◽  
Pollen And Spores

Meltwater from a 299-m-long ice core was filtered and analyzed for fossil pollen and spores. Pollen concentration was higher in the late Holocene and interglacial intervals (ca. 7 liter−1) than in the early Holocene and Wisconsinan (ca. 1–2 liter−1) ones. The late Holocene and interglacial assemblages were dominated by Alnus (alder), whereas the early Holocene and Wisconsinan ones were dominated by Betula (birch) and Artemisia (sage). During the Holocene and probably the last interglaciation, most of the pollen and spores were blown a minimum of 1000 km from low arctic shrub tundra and adjacent subarctic Picea (spruce) forest; these areas were dominated by the arctic air mass during the summer pollinating season. During the Wisconsinan-early Holocene, glacier ice and arctic air were more widespread and pollen sources were more distant; thus, at this time relatively little pollen was incorporated into the ice.The Devon ice-core data suggest that there should have been pollen in the continental ice sheet of Wisconsin time. When the ice sheet retreated this pollen would be carried by meltwater and redeposited with silt and clay together with contemporary pollen, producing an ecologically anomalous assemblage.

scholarly journals Ice-sheet flow features and rheological parameters derived from precise altimetric topography

1996 ◽  
Vol 23 ◽  
pp. 277-283 ◽  
Author(s):  
F. Rémy ◽  
C. Ritz ◽  
L. Brisset
Keyword(s):  
Shear Stress ◽  
Flow Direction ◽  
Ice Sheet ◽  
Rheological Parameters ◽  
Topographic Map ◽  
Radar Altimeter ◽  
Sheet Flow ◽  
Ice Flow ◽  
Exponential Factor ◽  
Flow Features

For the first time high-quality coverage of the ERS-1 radar altimeter provides a very accurate surface topographic map covering 80% of the Antarctic ice sheet that can contribute significantly to glaciological studies such as ice-sheet flow modelling. The topography allows estimation of the ice-flow direction, the balance velocity and the basal shear stress. A relationship between shear stress, basal temperature and a parameter related to strain rate helps in mapping the behaviour anomalies of these parameters. Longitudinal stress, sliding, bedrock topography and variation in the pre-exponential factor of the flow law are found to play a major role in the ice-flow pattern. This relation can also be used to estimate rheological parameters: the Glen exponent n is found to be 1 for T < −10°C and 3–4 for higher temperatures, where Q is found to be 70 kJ mol−1.

The late Quaternary stratigraphic record northwest of Montréal: regional ice-sheet dynamics, ice-stream activity, and early deglacial events

2006 ◽  
Vol 43 (4) ◽  
pp. 461-485 ◽  
Author(s):  
Martin Ross ◽  
Michel Parent ◽  
Beatriz Benjumea ◽  
James Hunter
Keyword(s):  
Late Quaternary ◽  
Late Glacial ◽  
Ice Flow ◽  
Glacial Sediments ◽  
Ice Stream ◽  
Digital Elevation ◽  
Flow Features ◽  
Ice Sheet Dynamics ◽  
Late Wisconsinan ◽  
Elevation Model

The Quaternary sediments of previously unstudied buried valleys and sections near Montréal are analyzed and other sites are revisited to further develop the stratigraphic framework of the St. Lawrence Lowland and to establish regional glacial and deglacial models. The southwest-trending buried valleys were investigated by stratigraphic drilling and high-resolution seismic profiling. The Quaternary succession consists, from base to top, of proximal glaciolacustrine sediments, two superposed till sheets (Argenteuil and Oka tills) of inferred Late Wisconsinan age, and Champlain Sea sediments. The glacial sediments of this sequence record an ice advance toward south (Argenteuil Till) followed by an abrupt ice-flow shift toward the southwest (Oka Till). Compositional and geomorphic data indicate that Oka Till is ubiquitous and is associated with a regional set of glacial landforms. The analysis of a regional digital elevation model in combination with published ice-flow indicators shows convergent flow patterns from the Ottawa–Montréal–Adirondack regions toward the Lake Ontario basin. Landforms produced by the inferred ice stream are locally crosscut by southward-trending ice-flow features. Hence southward flow in the upper St. Lawrence Valley seemingly took place in two distinct contexts: (1) during full glacial conditions, as ice margins stood at or near the late glacial maximum limits, and (2) during late deglaciation, as a post-ice stream reequilibration mechanism. Early deglacial events in the study area were also characterized by subglacial meltwater channelling and erosion along the valleys, subaquatic outwash deposition in glacial Lake Candona, and rapid infill of the valleys during the early stages of the ensuing Champlain Sea.

Late Wisconsinan glaciation of Amund and Ellef Ringnes islands, Nunavut: evidence for the configuration, dynamics, and deglacial chronology of the northwest sector of the Innuitian Ice Sheet

2003 ◽  
Vol 40 (3) ◽  
pp. 351-363 ◽  
Author(s):  
Nigel Atkinson
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Marine Fauna ◽  
Ice Flow ◽  
Ice Caps ◽  
Ice Cap ◽  
Sequential Entry ◽  
Data Record ◽  
Late Wisconsinan ◽  
Glacial Landforms

Geomorphic and chronologic evidence from Amund and Ellef Ringnes islands documents the configuration, dynamics, and collapse of the northwest sector of the Innuitian Ice Sheet. These data record the inundation of the Ringnes Islands by northwestward-flowing ice from divides spanning the alpine and lowland sectors of the Innuitian Ice Sheet. Ice-flow indicators and granite dispersal along eastern Amund Ringnes Island suggest Massey Sound was filled by an ice stream discharging coalescent alpine and lowland ice from Norwegian Bay. In contrast, the interior of Amund Ringnes Island was overridden by predominantly non-erosive, granite-free ice from a divide in the lowland sector of the ice sheet. Glacial landforms on Ellef Ringnes Island record coverage by largely non-erosive ice, but it remains uncertain whether these features relate to northward-flowing lowland ice or a cold-based local ice cap. Deglaciation of the Ringnes Islands commenced ~10 000 14C years ago. Deglacial dates between 9.7 and 9.2 ka BP record the sequential entry of marine fauna along Massey and Hassel sounds, concomitant with the southward retreat of trunk ice towards Norwegian Bay. These data suggest marine-based trunk glaciers were vulnerable to calving during pre-Holocene eustatic sea-level rise. However, deglacial dates from inner embayments indicate that residual ice caps persisted on Amund and Ellef Ringnes islands for 800 to 1400 14C years after retreat of trunk ice from the adjacent marine channels. Lateral meltwater channels record the subsequent retreat of these ice caps, which became increasingly confined within upland valleys after 8.6 ka BP.

scholarly journals Modeling the Cordilleran Ice Sheet

2007 ◽  
Vol 45 (3) ◽  
pp. 287-299 ◽  
Author(s):  
Barry L. Robert
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Time Dependent ◽  
Balance Function ◽  
Ice Flow ◽  
Radiocarbon Dates ◽  
Ice Growth ◽  
Flow Directions ◽  
Late Wisconsinan ◽  
Cordilleran Ice Sheet

ABSTRACT A time-dependent ice flow model is used to provide detailed reconstructions of ice growth and retreat for the southern portion of the Late Wisconsinan Cordilleran Ice Sheet. The two-dimensional, time-dependent model provides ice surface elevations and flow directions at a grid spacing of 15 km. Input to the model includes subglacial topography, a net mass balance function, and two ice flow parameters. The net mass balance function uses a polynomial equation to estimate equilibrium line altitude (ELA) across the study area. A quadratic equation is then used to provide net mass balance values as a function of elevation relative to the ELA. Late Wisconsinan glacial conditions are simulated by systematically lowering the ELA. The general timing of the model ice advance and retreat is tested against radiocarbon dated localities which place limits on the ice sheet's areal extent for different times during the Late Wisconsinan glaciation. In addition, glacial-geologic evidence directly attributable to the latest Cordilleran Ice Sheet is used in assessing the model reconstructions. Results from these experiments show that an ice growth and retreat chronology consistent with the limiting radiocarbon dates can be generated using the model, and provide information on flow directions and ice growth and retreat patterns.

scholarly journals Glacial and Sea Level History of Lowther and Griffith Islands, Northwest Territories: A Hint of Tectonics

2007 ◽  
Vol 47 (2) ◽  
pp. 133-145 ◽  
Author(s):  
Arthur S. Dyke
Keyword(s):  
Northwest Territories ◽  
Sea Level ◽  
Ice Sheet ◽  
Canadian Arctic ◽  
Laurentide Ice Sheet ◽  
Structural Elements ◽  
Ice Flow ◽  
Ice Load ◽  
Last Glaciation ◽  
History Of

ABSTRACT Lowther and Griffith islands, in the centre of Parry Channel, were overrun by the Laurentide Ice Sheet early in the last glaciation. Northeastward Laurentide ice flow persisted across at least Lowther Island until early Holocene déglaciation. Well constrained postglacial emergence curves for the islands confirm a southward dip of raised shorelines, contrary to the dip expected from the ice load configuration. This and previously reported incongruities may indicate regionally extensive tectonic complications of postglacial rebound aligned with major structural elements in the central Canadian Arctic Islands.

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