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

2010 ◽  
Vol 61 (2-3) ◽  
pp. 89-117 ◽  
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.

scholarly journals 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

2019 ◽  
Vol 92 (2) ◽  
pp. 469-482 ◽  
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.

Timing and Extent of Allerød and Younger Dryas Age (ca. 12,500–10,000 14C yr B.P.) Oscillations of the Cordilleran Ice Sheet in the Fraser Lowland, Western North America

2002 ◽  
Vol 57 (2) ◽  
pp. 208-224 ◽  
Author(s):  
Dori J. Kovanen ◽  
Don J. Easterbrook
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Glacier Retreat ◽  
Western North America ◽  
Radiocarbon Dates ◽  
Topographic Features ◽  
Juan De Fuca ◽  
Ice Retreat ◽  
Western Washington ◽  
Cordilleran Ice Sheet

AbstractThe use of shaded digital topographic models to visualizes suites of topographic features, stratigraphy, and field mapping reveals newly recognized multiple moraines associated with oscillations of the remnants of the Cordilleran Ice Sheet in the Fraser Lowland along the western Washington–British Columbia border. Morphologic features show the extent of ice represented by Sumas Drift (ca. 11,600–10,000 14C yr B.P.), following ca. 3000 yr of retreat from the glacial maximum (Fraser Glaciation) positions 80 km south of Seattle and in the Strait of Juan de Fuca. The paleogeography of the ice margin and timing of ice retreat during the Sumas Stade is reconstructed and bracketed by 70 radiocarbon dates (24 on marine shells, 46 on wood and peat), which are secured by morphologic and stratigraphic evidence. Four topographically distinct phases of the Sumas deglaciation model are suggested.Phase SI: 11,600–<11,400 14C yr B.P., outermost drift, scattered remnants of ice-contact depositsPhase SII: 11,600–11,400 14C yr B.P., glacier readvance, building prominent moraine followed by glacier retreatPhase SIII: 10,980–10,250 14C yr B.P., glacier readvance building of multiple moraines followed by glacier retreatPhase SIV: >10,250–10,000? 14C yr B.P., glacier readvance, building of inner moraine followed by glacier retreat

scholarly journals Late Wisconsinan deglaciation and glacial lake development in the Appalachians of southeastern Québec

2002 ◽  
Vol 53 (1) ◽  
pp. 117-135 ◽  
Author(s):  
Michel Parent ◽  
Serge Occhietti
Keyword(s):  
Flow Reversal ◽  
Laurentide Ice Sheet ◽  
Glacial Lake ◽  
Lawrence Estuary ◽  
Ice Stream ◽  
Flow Convergence ◽  
Ice Retreat ◽  
Late Wisconsinan ◽  
Appalachian Piedmont ◽  
St Lawrence Estuary

Abstract Late Wisconsinan deglaciation in southeastern Québec was preceded by a northward ice-flow reversal that was recorded in the northeastern part of the region. The reversal event was generated by flow convergence toward the St. Lawrence Ice Stream, a northeastward-flowing ice stream which formed in the St. Lawrence estuary prior to 13 000 years BP and lasted until at least 12 400 years BP. In the Bois-Francs uplands, the flow reversal event led to the formation of a semi-detached ice mass that underwent widespread stagnation and downwasting. In the southwestern region, northward retreat of the margin of the Laurentide Ice Sheet was marked by the formation of a series of discontinuous recessional moraines and by the development of ice-dammed lakes in the main valleys. The level of these lakes fell as progressively lower outlets became ice-free. The main episodes are (1) the Sherbrooke Phase of Glacial Lake Memphremagog, (2) an unnamed transitional lake and (3) Glacial Lake Candona, a large lake which had expanded northeastward from the deglaciated regions of the Upper St. Lawrence (Lake Iroquois) and Ottawa valleys to the Lake Champlain (Glacial Lake Vermont) basin. As recorded by the Danville Varves, Lake Candona lasted about 100 years following deposition of the Ulverton-Tingwick Moraine. Subsequent ice retreat along the Appalachian piedmont led to final drainage of Lake Candona and allowed Champlain Sea waters to invade much of these glaciolacustrine terrains about 12 000 years BP. On the basis of the Danville Varves record, a regional rate of ice retreat of about 200 m·a -1 is inferred. The age of the earliest moraine, the Frontier Moraine, is thus about 12 550 years BP, while the ages of the subsequent Dixville, Cherry River-East-Angus, Mont Ham and Ulverton-Tingwick moraines are estimated at 12 500, 12 325, 12 200 et 12 100 years BP, respectively.

scholarly journals Deglaciation and ice shelf development at the northeast margin of the Laurentide Ice Sheet during the Younger Dryas chronozone

Boreas ◽  
2017 ◽  
Vol 47 (1) ◽  
pp. 271-296 ◽  
Author(s):  
Mark F. A. Furze ◽  
Anna J. Pieńkowski ◽  
Morgan A. McNeely ◽  
Robbie Bennett ◽  
Alix G. Cage
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Laurentide Ice Sheet ◽  
Ice Shelf

scholarly journals Routing of meltwater from the Laurentide Ice Sheet during the Younger Dryas cold episode

Nature ◽  
1989 ◽  
Vol 341 (6240) ◽  
pp. 318-321 ◽  
Author(s):  
Wallace S. Broecker ◽  
James P. Kennett ◽  
Benjamin P. Flower ◽  
James T. Teller ◽  
Sue Trumbore ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Laurentide Ice Sheet ◽  
Cold Episode

Improved reconstruction of the southeastern Laurentide Ice Sheet deglaciation: constraining ice thinning using in-situ cosmogenic 10Be and 14C and critically evaluating different retreat rate chronometers

2020 ◽  
Author(s):  
Christopher Halsted ◽  
Jeremy Shakun ◽  
Lee Corbett ◽  
Paul Bierman ◽  
P. Thompson Davis ◽  
...  
Keyword(s):  
United States ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Ice Thickness ◽  
Northeastern United States ◽  
Terminal Moraine ◽  
Ice Volume ◽  
Ice Retreat ◽  
Exposure Ages

&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;To provide insight about ice sheet thinning history, we collected 120 samples for in-situ &lt;sup&gt;10&lt;/sup&gt;Be and 10 samples for in-situ &lt;sup&gt;14&lt;/sup&gt;C 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 &lt;sup&gt;10&lt;/sup&gt;Be remains from pre-Last Glacial Maximum periods of exposure, in-situ &lt;sup&gt;14&lt;/sup&gt;C is used to infer the erosional history and minimum exposure age of samples.&lt;/p&gt;&lt;p&gt;Presently, we have measured &lt;sup&gt;10&lt;/sup&gt;Be 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 (&gt;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&amp;#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&amp;#8211;12.9 ka), providing evidence of substantial ice volume loss during the B&amp;#248;lling-Aller&amp;#248;d warm period.&lt;/p&gt;&lt;p&gt;Our critical evaluation of deglacial chronometers, including valley-bottom &lt;sup&gt;10&lt;/sup&gt;Be 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.&lt;/p&gt;

scholarly journals Younger Dryas Interval and outflow from the Laurentide Ice Sheet

2000 ◽  
Vol 15 (1) ◽  
pp. 4-18 ◽  
Author(s):  
T. C. Moore ◽  
J. C. G. Walker ◽  
D. K. Rea ◽  
C. F. M. Lewis ◽  
L. C. K. Shane ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Laurentide Ice Sheet
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