An Introduction to the Continental Record of the Laurentide Ice Sheet

In the northeastern United States, there are extensive geochronologic and geomorphic constraints on the deglaciation of the southeastern Laurentide Ice Sheet; thus, it is an ideal area for large-scale ice volume reconstructions and comparison between different ice retreat chronometers. Varve chronologies, lake and bog-bottom radiocarbon ages, and cosmogenic nuclide exposure ages constrain the timing of ice retreat, but the inferred ages exhibit considerable noise and sometimes disagree. Additionally, there are few empirical constraints on ice thinning, forcing ice volume reconstructions to rely on geophysically-based ice thickness models. Here, we aim to improve the understanding of the southeastern Laurentide Ice Sheet recession by (1) adding extensive ice thickness constraints and (2) compiling all available deglacial chronology data in the region to investigate discrepancies between different chronometers.To provide insight about ice sheet thinning history, we collected 120 samples for in-situ 10Be and 10 samples for in-situ 14C cosmogenic exposure dating from various elevations at 13 mountains in the northeastern United States. By calculating ages of exposure at different elevations across this region, we reconstruct paleo-ice surface lowering of the southeastern Laurentide Ice Sheet during deglaciation. Where we suspect that 10Be remains from pre-Last Glacial Maximum periods of exposure, in-situ 14C is used to infer the erosional history and minimum exposure age of samples.Presently, we have measured 10Be in 73 samples. Mountain-top exposure ages located within 150 km of the southeastern Laurentide Ice Sheet terminal moraine indicate that near-margin thinning began early in the deglacial period (~19.5 to 17.5 ka), coincident with the slow initial margin retreat indicated by varve records. Exposure ages from several mountains further inland (>400 km north of terminal moraine) collected over ~1000 m of elevation range record rapid ice thinning between 14.5 and 13 ka. Ages within each of these vertical transects are similar within 1&#963; internal uncertainty, indicating that ice thinned quickly, less than a few hundred years at most. This rapid thinning occurred at about the same time that varve records indicate accelerated ice margin retreat (14.6&#8211;12.9 ka), providing evidence of substantial ice volume loss during the B&#248;lling-Aller&#248;d warm period.Our critical evaluation of deglacial chronometers, including valley-bottom 10Be ages from this project, is intended to constrain ice margin retreat rates and timing in the region. Ultimately, we will integrate our ice thickness over time constraints with the existing network of deglacial ages to create a probabilistic reconstructions of the southeastern Laurentide Ice Sheet volume during its recession through the northeastern United States.

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Landform assemblages produced by the Laurentide Ice Sheet in northeastern British Columbia and adjacent Northwest Territories — constraints on glacial lakes and patterns of ice retreatThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.

Canadian Journal of Earth Sciences ◽

10.1139/e07-053 ◽

2008 ◽

Vol 45 (5) ◽

pp. 593-610 ◽

Cited By ~ 7

Author(s):

Jan M. Bednarski

Keyword(s):

British Columbia ◽

Northwest Territories ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Ice Flow ◽

The North ◽

Relative Chronology ◽

Mountain Front ◽

Ice Retreat ◽

Cordilleran Ice Sheet

The Laurentide Ice Sheet reached the Canadian Cordillera during the last glacial maximum in northeastern British Columbia and adjacent Northwest Territories and all regional drainage to unglaciated areas in the north was dammed by the ice. Converging ice-flow patterns near the mountain front suggest that the Laurentide Ice Sheet likely coalesced with the Cordilleran Ice Sheet during the last glaciation. With deglaciation, the ice masses separated, but earlier ice retreat in the south meant that meltwater pooled between the mountain front and the Laurentide margin. The level of the flooding was controlled by persistent ice cover on the southern Franklin Mountains. Glacial Lake Liard formed when the Laurentide Ice Sheet retreated east of the southern Liard Range and, at its maximum extent, may have impounded water at least as far south as the Fort Nelson River. Deglaciation of the plains was marked by local variations in ice flow caused by a thin ice sheet becoming more affected by the topography and forming lobes in places. These lobes caused diversions in local drainage readily traced by abandoned meltwater channels. Radiocarbon ages from adjacent areas suggest the relative chronology of deglaciation presented here occurred between 13 and 11 ka BP.

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The recession of the Laurentide Ice Sheet in southeast Northwest Territories during the Pleistocene-Holocene transition

10.5194/egusphere-egu2020-5410 ◽

2020 ◽

Author(s):

Samuel E. Kelley ◽

Brent Ward ◽

Jason Briner ◽

Martin Ross ◽

Philippe Normandeau ◽

...

Keyword(s):

Northwest Territories ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Glacial Lake ◽

Lake Basin ◽

Great Slave Lake ◽

Northwestern Margin ◽

Ice Retreat ◽

Oriented Parallel ◽

Exposure Ages

The Laurentide Ice Sheet (LIS) during the Pleistocene-Holocene transition provides a useful natural laboratory for examining the behavior of a mid- to high-latitude ice sheet during a period of climatically driven ice sheet thinning and retreat. While the timing and pattern of Pleistocene recession of the LIS are well-constrained along the southern and eastern margins, there is limited chronology constraining the ice margin retreat along the northwestern margin. Here we present new cosmogenic 10Be exposure ages retreat of the western margin of the LIS during the Pleistocene-Holocene transition. Sampling was performed along three transects located between the northern shore of Great Slave Lake and Lac de Gras. Each of the transects is oriented parallel to the inferred ice retreat direction in an attempt to capture a regional rate of retreat. Our new 10Be cosmogenic exposure ages from the southeastern Northwest Territories demonstrate that regional deglaciation occurred around 11,000 years ago. The population of ages broadly overlaps, indicating that either the retreat occurred within the resolution of our chronology or that the ice sheet experienced widespread stagnation and rapid down-wasting. These ages, not corrected for changes in atmospheric depth due to isostatic rebound, are older than minimum limiting radiocarbon constraints by ~1000 years, indicating that existing LIS reconstructions may underestimate the timing and pace of ice margin recession for this sector. Constraining the timing of the recession of the northwest sector of the LIS has the potential to inform our understanding about the damming of large proglacial lakes, such as Glacial Lake McConnell. The ages from our southern transect, collected from elevated bedrock hills, indicate LIS retreat from through the McConnell basin occurred after 12,000 years ago, and thus constitute maximum limiting constraints on the expansion of Glacial Lake McConnell southeastward into the present-day Great Slave Lake basin. Our chronology, combined with other emerging cosmogenic exposure ages constraining LIS deglaciation indicates retreat of the ice margin over 100s of kilometres during the Pleistocene-Holocene transition, exhibiting no evidence of a significant readvance during the Younger Dryas stadial.

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Late Wisconsin Advance and Retreat Pattern in the Miami Sublobe, Laurentide Ice Sheet

Annals of Glaciology ◽

10.1017/s026030550000851x ◽

1990 ◽

Vol 14 ◽

pp. 172-175 ◽

Cited By ~ 1

Author(s):

Thomas V. Lowell ◽

Robert Stuckenrath

Keyword(s):

Climatic Change ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Maximum Extent ◽

Southern Margin ◽

Radiometric Ages ◽

A Site ◽

Age Estimates

Ice-sheet advance and retreat chronologies reflect climatic change in a manner that is difficult to decipher. Especially difficult is the placement of records into a chronologic sequence. Multiple age estimates obtained from three stratigraphic positions at a site in Ohio show that organics within deposits of the Miami sublobe, along the southern margin of the Laurentide ice sheet, may be up to 3000 years older than the age of the maximum Late Wisconsin extension of that sublobe. In addition, recent studies on organic accumulations above glacial drift provide bracketing ages for ice recession. When the existing radiometric ages for the Miami sublobe are interpreted with these new radiometric constraints, several fluctuations suggested by prior workers are unsupported. A simpler chronology for the Miami sublobe suggests that in late Wisconsin time the southern margin of the Laurentide ice sheet advanced through Ohio about 22 ka to its maximum extent at 19.7 and remained near there until 15 ka. This is in agreement with newly-refined stratigraphic histories of other Laurentide lobes.

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Beryllium-10 dating of the Foothills Erratics Train in Alberta, Canada, indicates detachment of the Laurentide Ice Sheet from the Rocky Mountains at ~15 ka

Quaternary Research ◽

10.1017/qua.2019.10 ◽

2019 ◽

Vol 92 (2) ◽

pp. 469-482 ◽

Cited By ~ 4

Author(s):

Martin Margold ◽

John C. Gosse ◽

Alan J. Hidy ◽

Robin J. Woywitka ◽

Joseph M. Young ◽

...

Keyword(s):

Rocky Mountains ◽

Ice Sheet ◽

Younger Dryas ◽

Rocky Mountain ◽

Laurentide Ice Sheet ◽

Exposure Dating ◽

Mountain Front ◽

Ice Retreat ◽

Cordilleran Ice Sheet ◽

Latitudinal Trend

AbstractThe Foothills Erratics Train consists of large quartzite blocks of Rocky Mountains origin deposited on the eastern slopes of the Rocky Mountain Foothills in Alberta between ~53.5°N and 49°N. The blocks were deposited in their present locations when the western margin of the Laurentide Ice Sheet (LIS) detached from the local ice masses of the Rocky Mountains, which initiated the opening of the southern end of the ice-free corridor between the Cordilleran Ice Sheet and the LIS. We use 10Be exposure dating to constrain the beginning of this decoupling. Based on a group of 12 samples well-clustered in time, we date the detachment of the western LIS margin from the Rocky Mountain front to ~14.9 ± 0.9 ka. This is ~1000 years later than previously assumed, but a lack of a latitudinal trend in the ages over a distance of ~500 km is consistent with the rapid opening of a long wedge of unglaciated terrain portrayed in existing ice-retreat reconstructions. A later separation of the western LIS margin from the mountain front implies higher ice margin–retreat rates in order to meet the Younger Dryas ice margin position near the boundary of the Canadian Shield ~2000 years later.

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Luminescence dating of mid- to Late Wisconsinan aeolian sand as a constraint on the last advance of the Laurentide Ice Sheet across the Tuktoyaktuk Coastlands, western Arctic Canada

Canadian Journal of Earth Sciences ◽

10.1139/e07-015 ◽

2007 ◽

Vol 44 (6) ◽

pp. 857-869 ◽

Cited By ~ 21

Author(s):

Julian B Murton ◽

Manfred Frechen ◽

Darrel Maddy

Keyword(s):

Ice Sheet ◽

Luminescence Dating ◽

The Arctic ◽

Laurentide Ice Sheet ◽

Liverpool Bay ◽

Infrared Stimulated Luminescence ◽

Western Arctic ◽

Late Wisconsinan ◽

Age Estimates ◽

The Last Glacial

Luminescence dating of pre-glacial sand in the Tuktoyaktuk Coastlands, Northwest Territories, discounts an Early Wisconsinan age for the last Laurentide glaciation to cross the Arctic Coastal Plain and supports a Late Wisconsinan age. Aeolian dune sand from the Kittigazuit Formation near Cliff Point, on the southern shore of Liverpool Bay, predates till deposited during the Toker Point Stade. Potassium-rich feldspar from three stratigraphic sections ~35 km up-ice from the Toker Point glacial limit provides thermoluminescence age estimates that range from 18.7 ± 2.0 to 9.1 ± 1.0 ka and infrared stimulated luminescence age estimates of 23.8 ± 5.1 to 11.0 ± 2.1 ka. Quartz from four of the same samples provides optically stimulated luminescence age estimates of 16.5 ± 1.0 to 13.7 ± 0.9 ka. Collectively, these estimates reject the Early Wisconsinan age for the Toker Point Stade glaciation inferred hitherto from radiocarbon dating. A review of pre-glacial and post-glacial age estimates from the region indicates that during the Toker Point Stade ice advanced across the Tuktoyaktuk Coastlands no earlier than ~30 ka, and probably not before ~22 ka. Deglaciation had certainly commenced by 14.3 ka, and probably by ~16 ka. The Toker Point glaciation, therefore, dates approximately to the last glacial maximum, reinforcing the interpretation of the late rebuild up of the Laurentide Ice Sheet that characterized many parts of its margin.

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The Saint-Narcisse morainic complex and early Younger Dryas events on the southeastern margin of the Laurentide Ice Sheet

Géographie physique et Quaternaire ◽

10.7202/038987ar ◽

2010 ◽

Vol 61 (2-3) ◽

pp. 89-117 ◽

Cited By ~ 18

Author(s):

Serge Occhietti

Keyword(s):

Ice Sheet ◽

Younger Dryas ◽

Laurentide Ice Sheet ◽

General Outline ◽

Lawrence Estuary ◽

Ottawa River ◽

Topographic Features ◽

Southeastern Margin ◽

Ice Retreat ◽

St Lawrence Estuary

Abstract The Saint-Narcisse morainic complex extends over 750 km along the southern margin of the Laurentian Highlands in Québec, north of the St. Lawrence Valley, between the Ottawa and Saguenay Rivers. To the east, the Laurentide Ice Sheet margin was located in the present St. Lawrence Estuary. To the west, the morainic complex is extended 235 km west of the Ottawa River to the Algonquin Highlands, in Ontario. The general outline of the morainic complex comprises large lobes and reentrants, related to major topographic features. In the lower Saint-Maurice River area, the moraine is composed of reworked clay and till and proximal glaciomarine deposits (Yamachiche Diamicton) and melt-out till and ice-marginal outwash (Charette Drift). The Saint-Narcisse Event can be subdivided in several phases: local readvance in low areas, main phase at the origin of the Saint-Narcisse Moraine s.s., melting-out of the marginal ice with compressive structures and large proglacial outwash features, and slow retreat with secondary ridges. The accuracy of the chronological data is limited by several factors: and a floating chronology is proposed. Two landmarks constrain the age and range of duration of the main Saint-Narcisse phase. The main ridge deposition occured after the onset, ca. 12.9 cal ka, of Champlain Sea in the St. Lawrence Valley, and a rapid ice retreat on the southern edge of the Laurentians. It ended before the drawdowm, in the Lake Huron basin, of Glacial Lake Algonquin ca. 12.5 cal ka. The Saint-Narcisse Event is related to the early cold phase of Younger Dryas, as evidenced by other YD ice readvances in Maine, Nova Scotia, and ice cover on the Gaspé Peninsula. It corresponds to a positive change of the budget of the Laurentide Ice Sheet as a result of climate forcing. After a slow ice front retreat during about 900-700 yr, the final phase of YD is marked by the Mars-Batiscan Moraine, located 17 to 70 km north of the Saint-Narcisse Moraine.

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Late Wisconsin Advance and Retreat Pattern in the Miami Sublobe, Laurentide Ice Sheet

Annals of Glaciology ◽

10.3189/s026030550000851x ◽

1990 ◽

Vol 14 ◽

pp. 172-175 ◽

Cited By ~ 1

Author(s):

Thomas V. Lowell ◽

Robert Stuckenrath

Keyword(s):

Climatic Change ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Maximum Extent ◽

Southern Margin ◽

Radiometric Ages ◽

A Site ◽

Age Estimates

Ice-sheet advance and retreat chronologies reflect climatic change in a manner that is difficult to decipher. Especially difficult is the placement of records into a chronologic sequence. Multiple age estimates obtained from three stratigraphic positions at a site in Ohio show that organics within deposits of the Miami sublobe, along the southern margin of the Laurentide ice sheet, may be up to 3000 years older than the age of the maximum Late Wisconsin extension of that sublobe. In addition, recent studies on organic accumulations above glacial drift provide bracketing ages for ice recession. When the existing radiometric ages for the Miami sublobe are interpreted with these new radiometric constraints, several fluctuations suggested by prior workers are unsupported. A simpler chronology for the Miami sublobe suggests that in late Wisconsin time the southern margin of the Laurentide ice sheet advanced through Ohio about 22 ka to its maximum extent at 19.7 and remained near there until 15 ka. This is in agreement with newly-refined stratigraphic histories of other Laurentide lobes.

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Evidence from thermoluminescence dating for Middle Wisconsinan deglaciation in the Hudson Bay Lowland of Manitoba

Canadian Journal of Earth Sciences ◽

10.1139/e91-023 ◽

1991 ◽

Vol 28 (2) ◽

pp. 240-249 ◽

Cited By ~ 20

Author(s):

Glenn W. Berger ◽

E. Nielsen

Keyword(s):

River Sediments ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Hudson Bay ◽

Climatic Warming ◽

Sediment Dating ◽

Thermoluminescence Dating ◽

Hudson Bay Lowland ◽

Age Estimates

We report here the first direct dating of the nonglacial, intertill Nelson River sediments from five sites in northern Manitoba. We used the thermoluminescence (TL) sediment-dating technique to obtain age estimates of 32–46 ka for four samples and 119 ka for the fifth, all samples previously correlated to the Sangamonian Stage (80–130 ka) Missinaibi Formation. We interpret the younger TL dates as being within 20–40% of the true deposition ages, but interpret the oldest TL date as an overestimate because of ineffective zeroing of the light-sensitive TL associated with observed pebble and sand detritus in that sample. Thus these younger direct dates imply a significant climatic warming and deglaciation in the heart of the Laurentide Ice Sheet area during Middle Wisconsinan time.

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Chronology of advance and recession dynamics of the southern Green Bay Lobe of the Laurentide Ice Sheet, south-central Wisconsin, USA

Quaternary Research ◽

10.1017/qua.2020.8 ◽

2020 ◽

Vol 95 ◽

pp. 142-153

Author(s):

Eric C. Carson ◽

John W. Attig ◽

J. Elmo Rawling ◽

Paul R. Hanson ◽

Stefanie E. Dodge

Keyword(s):

Ice Sheet ◽

Marine Isotope Stage ◽

Laurentide Ice Sheet ◽

Time Interval ◽

Green Bay ◽

Ams Radiocarbon Dating ◽

South Central ◽

Southern Margin ◽

Osl Age ◽

Age Estimates

AbstractWe used a combination of accelerator mass spectrometry (AMS) radiocarbon dating, optically stimulated luminescence (OSL) age estimates, and stratigraphic data from cores collected along the southern margin of the Green Bay Lobe (GBL) of the Laurentide Ice Sheet to provide new information on the timing and dynamics of the end of advance of the GBL and the dynamics of the ice sheet while very near its maximum position. Coring at multiple sites along the margin of the GBL indicate that ice had reached a stable position near its maximum extent by 24.7 ka; that ice advanced several kilometers to the Marine Isotope Stage 2 maximum position sometime shortly after 21.2 ka; and that ice remained at or beyond that position through the time interval represented by an OSL age estimate of 19.2 ± 3.2 ka. The timeline developed from these chronological data is internally consistent with, and further refines, AMS radiocarbon ages and OSL age estimates previously published for the southern margin of the GBL. It also provides new chronological control on the expansion of the GBL from its late Marine Isotope Stage (MIS) 3 extent to its MIS 2 maximum.

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