The Laurentide Ice Sheet and An Introduction To the Quaternary Geology of the Canadian Shield [Chapter 3: Quaternary Geology of the Canadian Shield]

The Little Bear River section lies in a transition zone between Mackenzie Lowland and Canyon Ranges of Mackenzie Mountains. Within the transition zone, the maximum extent of the Laurentide ice sheet overlaps the former extent of montane glaciers that emanated from the higher parts of Canyon Ranges or from the still higher Backbone Ranges to the southwest. Five montane tills, each with a paleosol developed in its upper part, indicate five separate glaciations during each of which a valley glacier emanating from the headwaters of Little Bear River extended eastward into the transition zone. The uppermost of the montane tills is overlain by boulder gravel containing rocks of Canadian Shield origin deposited by the Laurentide ice sheet.Solum and B horizon depths, red colours, and lack of leaching and cryoturbation indicate that although each successive interglacial interval was cooler than the preceding one, even the last of the intervals was warmer than the Holocene. Climatic conditions during one of the intervals inferred from the paleobotanic data, particularly spruce forest development, are consistent with conditions inferred from the associated paleosol.The uppermost of the montane tills is thought to correlate with till of Reid (Illinoian) age in central Yukon. The paleosol developed on that till is, accordingly, thought to correlate with the Diversion Creek paleosol developed on drift of Reid age. The Laurentide boulder gravel is assigned to a stade of Hungry Creek Glaciation of Late Wisconsinan age. The Laurentide ice sheet reached its apparent all-time western limit during the Hungry Creek Glaciation maximum.

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Drift carbonate on the Canadian Shield. II: Carbonate dispersal and ice-flow patterns in northern Manitoba

Canadian Journal of Earth Sciences ◽

10.1139/e88-073 ◽

1988 ◽

Vol 25 (5) ◽

pp. 783-787 ◽

Cited By ~ 17

Author(s):

L. A. Dredge

Keyword(s):

Acid Rain ◽

Ice Sheet ◽

Flow Patterns ◽

Canadian Shield ◽

Lake Acidification ◽

Laurentide Ice Sheet ◽

Ice Streams ◽

Dispersal Pattern ◽

Ice Flow ◽

Natural Lake

In northern Manitoba, carbonates were glacially dispersed westwards for distances up to 260 km beyond the limit of carbonate bedrock. The dispersal pattern in the surface till reflects the interaction of Keewatin and Hudson – Labrador ice in the region during the Wisconsin glaciation and suggests the presence of ice streams within the Laurentide Ice Sheet. Pre-Wisconsinan tills show different dispersal and ice-flow patterns. In unfrozen terrain, carbonate till sheets on the Shield buffer the effects of natural lake acidification and acid rain; however, their ability to buffer appears to be severely limited in permafrost terrain.

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Cosmogenic 36Cl dating of the maximum limit of the Laurentide Ice Sheet in southwestern Alberta

Canadian Journal of Earth Sciences ◽

10.1139/e99-038 ◽

1999 ◽

Vol 36 (8) ◽

pp. 1347-1356 ◽

Cited By ~ 32

Author(s):

Lionel E Jackson, Jr. ◽

Fred M Phillips ◽

Edward C Little

Keyword(s):

Rocky Mountains ◽

Erosion Rate ◽

Ice Sheets ◽

Ice Sheet ◽

Canadian Shield ◽

Laurentide Ice Sheet ◽

Glacial Deposits ◽

Glacial Ice ◽

Continental Ice Sheets ◽

Glacial Advance

Cosmogenic 36Cl ages were determined on 11 glacial erratics from the summits of Porcupine Hills and Cloudy Ridge, Waterton valley, and the Foothills south of Cardston, Alberta. These erratics were derived from the Canadian Shield and the Rocky Mountains of the Waterton area. They were laid down by (1) the most extensive advance of a Canadian Shield centred continental ice sheet into this region (stratigraphically oldest glacial deposits); (2) a montane glacial advance from the Waterton valley (stratigraphically intermediate glacial deposits); and (3) an advance of continental glacial ice that overrode deposits of the intermediate-age montane advance. Zero erosion rate 36Cl ages of the erratics, uncorrected for snow cover, range between about 12 and 18 ka. They support the hypothesis that the Laurentide Ice Sheet reached farther into the southwestern Foothills than did all the previous continental ice sheets.

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Revised chronology of northwest Laurentide ice-sheet deglaciation from beryllium-10 exposure-dated erratics on the western Canadian Shield

10.5194/egusphere-egu2020-13198 ◽

2020 ◽

Author(s):

Alberto Reyes ◽

Anders Carlson ◽

Jesse Reimink

Keyword(s):

Climate Change ◽

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Canadian Shield ◽

Laurentide Ice Sheet ◽

Exposure Dating ◽

Poor Region ◽

A Site ◽

Exposure Ages

The timing of northwest Laurentide ice-sheet deglaciation is important for understanding how ice-sheet retreat, and associated meltwater discharge, may have been involved in abrupt climate change and rapid sea-level rise at the end of the last glaciation. However, the deglacial chronology across the western Canadian Shield is poorly understood, with only a handful of minimum-limiting 14C dates and sparse cosmogenic nuclide exposure dates constraining the timing and pattern of northwest Laurentide ice-sheet retreat across >1000 km of ice-sheet retreat to the marine limit west of Hudson Bay. We present cosmogenic 10Be surface exposure dating of glacial erratics at two sites, within a ~160,000 km2 region with no reliable temporal constraints on ice-margin retreat, to directly date the timing of northwest Laurentide ice-sheet deglaciation. Six erratics perched directly on bedrock at a site on the western edge of the Slave Craton have exposure ages between 12.8&#177;0.6 and 12.2&#177;0.6 thousand years ago (ka;&#160;&#177;1sigma). Five erratics on bedrock, sampled at a site 115 km up-ice to the east, yielded exposure ages between 10.8&#177;0.5 and 11.6&#177;0.5 ka. When corrected for decreased atmospheric depth due to isostatic uplift since deglaciation, the error-weighted mean ages for the two sites indicate that the Laurentide ice sheet retreated through this region of the western Canadian Shield between 13.3&#177;0.2 and 11.8&#177;0.2 ka, or at least 1 kyr earlier than inferred from the canonical compilation of minimum-limiting 14C dates for deglaciation and paleo-glaciological models. We tentatively infer a preliminary ice-margin retreat rate of ~0.1 m kyr-1&#160;over this interval spanning much of the Younger Dryas which, compared to earlier estimates, implies a substantially lower volume of meltwater flux from the retreating northwest Laurentide ice sheet at this time. &#160;Additional exposure ages on glacial erratics across this data-poor region are needed for validation of existing deglacial ice-sheet models, which can in turn contribute to comprehensive testing of hypotheses related to northwest Laurentide ice-sheet retreat rate, abrupt deglacial sea-level rise, and potential forcing of associated climate change events.

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Exploring the use of zircon geochronology as an indicator of Laurentide Ice Sheet till provenance, Indiana, USA

Quaternary Research ◽

10.1017/qua.2017.71 ◽

2017 ◽

Vol 88 (3) ◽

pp. 525-536 ◽

Cited By ~ 1

Author(s):

Christine M. Kassab ◽

Samantha L. Brickles ◽

Kathy J. Licht ◽

G. William Monaghan

Keyword(s):

Lake Michigan ◽

Ice Sheet ◽

Canadian Shield ◽

Laurentide Ice Sheet ◽

Michigan Basin ◽

Zircon Geochronology ◽

Ice Flow ◽

Zircon Age ◽

Population Distributions ◽

Path Models

AbstractA pilot study was designed to evaluate the potential of zircon geochronology as a provenance indicator of till from the Lake Michigan, Saginaw, and Huron-Erie Lobes of the Laurentide Ice Sheet. Based on existing ice flow-path models, we hypothesized that till from each lobe would have different zircon age population distributions because the lobes originated from regions of the Canadian Shield with different bedrock ages. After correcting for zircon fertility, the majority of grains in all till samples are 1600–950 Ma, with ~30 % of ages >2500 Ma. This similarity means that till from the three lobes cannot be clearly differentiated based on their zircon populations. The dominant ages found and the homogeneity of distributions in the till indicates a non-Shield source and, instead, reflect an origin from some combination of underlying till and sedimentary bedrock in the Great Lakes region. Even though the datasets are small, the tills have similarities to zircon distributions in Michigan Basin rocks. This implies that a substantial fraction of zircon in till was not transported long distances from the Canadian Shield. Although zircon ages are not distinct between tills, the method provides a novel application to understand Laurentide Ice Sheet glacial erosion and transport.

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Displacement of Salt by the Laurentide Ice Sheet

Quaternary Research ◽

10.1016/0033-5894(92)90040-p ◽

1992 ◽

Vol 38 (3) ◽

pp. 305-315 ◽

Cited By ~ 6

Author(s):

William A. White

Keyword(s):

New York ◽

North America ◽

Ice Sheet ◽

Canadian Shield ◽

Laurentide Ice Sheet ◽

Glacial Erosion ◽

Saginaw Bay ◽

Central New York ◽

Lower Peninsula ◽

Salt Deposits

AbstractIn central New York, deformation of salt of the Salina Formation by the Laurentide Ice Sheet is shown by a thinning of the salt stratum in and near the outcrop zone where it was overridden by the ice sheet and by a thickening down-dip near the glacial limit. Less definitive suggestions of deformation by glacial overriding of the Salina outcrop zone in northeastern Ohio are seen in salt-cored anticlines in the vicinity of the glacial limit. In the lower peninsula of Michigan, isopachs of salt curve around Saginaw Bay, which suggests that the salt was displaced southwestward, away from the bay, by pressure of the Saginaw lobe of the ice sheet. All but one of the major Paleozoic salt deposits of North America lie in a zone that girdles two-thirds of the Canadian Shield from where glacial erosion removed all but occasional outliers of Phanerozoic strata.

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