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.

Laurentide and montane glaciation along the Rocky Mountain Foothills of northeastern British Columbia

2007 ◽  
Vol 44 (4) ◽  
pp. 445-457 ◽  
Author(s):  
Jan M Bednarski ◽  
I Rod Smith
Keyword(s):  
British Columbia ◽  
Ice Sheet ◽  
Rocky Mountain ◽  
Laurentide Ice Sheet ◽  
Cosmogenic Dating ◽  
Surficial Geology ◽  
Continental Divide ◽  
Mountain Front ◽  
Late Wisconsinan ◽  
Cordilleran Ice Sheet

Mapping the surficial geology of the Trutch map area (NTS 94G) provides new data on the timing of continental and montane glaciations along the Foothills of northeastern British Columbia. Striated surfaces on mountain crests were dated to the Late Wisconsinan substage by cosmogenic dating. The striations were produced by eastward-flowing ice emanating from the region of the Continental Divide. This ice was thick enough to cross the main ranges and overtop the Rocky Mountain Foothill summits at 2000 m above sea level (asl). It is argued here that such a flow, unhindered by topography, could only have been produced by the Cordilleran Ice Sheet and not by local cirque glaciation. During this time, the Cordilleran Ice Sheet dispersed limestone and schist erratics of western provenance onto the plains beyond the mountain front. Conversely, the Laurentide Ice Sheet did not reach its western limit in the Foothills until after Cordilleran ice retreated from the area. During its maximum, the Laurentide ice penetrated the mountain valleys up to 17 km west of the mountain front, and deposited crystalline erratics from the Canadian Shield as high as 1588 m asl along the Foothills. In some valleys a smaller montane advance followed the retreat of the Laurentide Ice Sheet.

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.

2008 ◽  
Vol 45 (5) ◽  
pp. 593-610 ◽  
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.

Late Wisconsinan Cordilleran and Laurentide glaciation of the Peace River Valley east of the Rocky Mountains, British Columbia

2018 ◽  
Vol 55 (12) ◽  
pp. 1324-1338 ◽  
Author(s):  
Gregory M.D. Hartman ◽  
John J. Clague ◽  
René W. Barendregt ◽  
Alberto V. Reyes
Keyword(s):  
Rocky Mountains ◽  
Ice Sheet ◽  
River Valley ◽  
Laurentide Ice Sheet ◽  
Eastern Front ◽  
Peace River ◽  
Stratigraphic Framework ◽  
Mountain Front ◽  
Late Wisconsinan ◽  
Cordilleran Ice Sheet

In the past, researchers have disagreed over the maximum extent of the Cordilleran Ice Sheet in the Peace River valley during the Late Wisconsinan. Some workers argued that Cordilleran ice reached beyond the Rocky Mountains and briefly coalesced with the Laurentide Ice Sheet on the westernmost Interior Plains. In contrast, others asserted that Cordilleran ice did not reach beyond the eastern front of the Rocky Mountains. Stratigraphic interpretation of three sections within a Middle Wisconsinan paleovalley and re-examination of a previously published regional stratigraphic framework show that western-sourced ice (likely the Cordilleran Ice Sheet) extended east of the mountain front during the Late Wisconsinan, prior to the incursion of the Laurentide Ice Sheet into the area. This conclusion has implications for Cordilleran Ice Sheet reconstruction and modelling, and provides insight into the interactions between the Cordilleran and Laurentide ice sheets during the last glaciation.

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.

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

The deglacial dynamics of the Laurentide and Cordilleran ice sheets in the Mackenzie Mountains, Northwest Territories, Canada

2021 ◽  
Author(s):  
Benjamin J Stoker ◽  
Martin Margold ◽  
Duane G. Froese ◽  
John C. Gosse
Keyword(s):  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Geomorphological Mapping ◽  
Dating Methods ◽  
Mountain Front ◽  
Modelling Studies ◽  
Mackenzie Mountains ◽  
Cordilleran Ice Sheet ◽  
The Individual ◽  
Glacial Landforms

&lt;p&gt;The northwestern sector of the Laurentide Ice Sheet coalesced with the Cordilleran Ice Sheet over the southern Mackenzie Mountains, and with local montane glaciers along the eastern slopes of the Mackenzie Mountains. Numerical modelling studies have identified rapid ice sheet thinning in this region as a major contributor to Meltwater Pulse 1A. Despite advances in remote sensing and numerical dating methods, the configuration and chronology of the northwestern sector of the Laurentide Ice Sheet have not been reconstructed in detail. The last available studies date back to the 1990s, when field surveys and mapping from aerial imagery were used to reconstruct the glacial history in the Mackenzie Mountains. Cross-cutting relations between glacial landforms and a series of &lt;sup&gt;36&lt;/sup&gt;Cl cosmogenic nuclide dates were used to propose a deglacial model involving a significant readvance of the Laurentide Ice Sheet in the region. However, the chronological evidence supporting the readvance is uncertain because the individual ages are few and poorly clustered. Here we present an updated map of the glacial limits during the local Last Glacial Maximum and the recessional record in the Mackenzie Mountains, based on glacial geomorphological mapping from the ArcticDEM. We provide sixteen new&amp;#160;&lt;sup&gt;10&lt;/sup&gt;Be dates from four sites that were previously glaciated by the Laurentide Ice Sheet to constrain the deglacial sequence across the region. These dates indicate ice sheet detachment from the eastern Mackenzie Mountains at ~16 ka as summits in the mountain front became ice-free. The Mackenzie Valley at ~ 65 &amp;#176;N became ice-free at ~ 14 &amp;#8211; 13&amp;#160; ka, towards the end of the B&amp;#248;lling-Aller&amp;#248;d warm period. Combining these dates with existing &lt;sup&gt;10&lt;/sup&gt;Be dates, these chronological constraints on the deglaciation of the Laurentide Ice Sheet allow us to reinterpret landform relations in the Mackenzie Mountains in order to reconstruct the ice sheet retreat. Our reconstruction provides updated constraints on the LGM extent, and the timing and pattern of deglaciation in the Mackenzie Mountains. This new understanding is useful to future efforts to quantify past sea-level contributions from the western Laurentide Ice Sheet.&lt;/p&gt;

Glacial history and stratigraphy of the Alberta portion of the Kananaskis Lakes map area

1980 ◽  
Vol 17 (4) ◽  
pp. 459-477 ◽  
Author(s):  
L. E. Jackson Jr.
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Rocky Mountain ◽  
Laurentide Ice Sheet ◽  
Glacial History ◽  
Mountain Valley ◽  
Eastern Margin ◽  
Mountain Front ◽  
Late Wisconsinan ◽  
Land Mammal

Deposits of till, glaciofluvial, and glaciolacustrine sediments representing four glaciations are recognized in the Alberta portions of the Kananaskis Lakes 1:250 000 map sheet (82J). The oldest episode is represented by scattered erratics and patches of till above 1400 m in the Porcupine Hills. This episode involved nonsynchronous advances of Laurentide and Rocky Mountain ice sheets. The next glacial episode involved coalescence of Rocky Mountain and Laurentide ice in the eastern Foothills, north of the Porcupine Hills. The Rocky Mountain Maycroft Till, the Laurentide Maunsell Till, and the glaciolacustrine Chain Lakes Clays and Silts were deposited during this episode. The next glaciation involved the last coalescence of Rocky Mountain and Laurentide ice sheets in the vicinity of the study area. The Rocky Mountain Bow Valley Till and the mixed Rocky Mountain – Laurentide provenance Erratics Train Till were deposited during this episode along with the Foothills Erratics Train. The latest glaciation involved an advance of the Laurentide ice sheet to the eastern margin of the study area and Rocky Mountain valley glaciers to the mountain front. One readvance of Rocky Mountain valley glaciers during retreat is recognized. The glaciolacustrine Midnapore Silts and Clays were deposited due to Laurentide ice damming of Bow River valley while the Canmore and Eisenhower Junction Tills were deposited by valley glaciers. On the basis of land mammal chronology, the two oldest glaciations are believed to be Illinoian in age. Radiocarbon evidence indicates the Erratics Train Glaciation to be at least Early Wisconsinan in age and the post-Erratics Train to be of Late Wisconsinan age.

scholarly journals Late Pleistocene glacial chronologies and paleoclimate in the northern Rocky Mountains

2021 ◽  
Author(s):  
Brendon Quirk ◽  
Elizabeth Huss ◽  
Benjamin Laabs ◽  
Eric Leonard ◽  
Joseph Licciardi ◽  
...  
Keyword(s):  
Rocky Mountains ◽  
Ice Sheet ◽  
Northern Rocky Mountains ◽  
Mountain Ranges ◽  
Mountain Glaciers ◽  
Continental Divide ◽  
Ice Retreat ◽  
Geologic Record ◽  
Glacier Modeling ◽  
Exposure Ages

Abstract. The geologic record of mountain glaciations is a robust indicator of terrestrial paleoclimate change. During the last glaciation, mountain ranges across the western U.S. hosted glaciers while the Cordilleran and Laurentide ice sheets flowed to the west and east of the continental divide, respectively. Records detailing the chronologies and paleoclimate significance of these ice advances have been developed for many sites across North America. However, relatively few glacial records have been developed for mountain glaciers in the northern Rocky Mountains near ice sheet margins. Here, we report cosmogenic beryllium-10 surface exposure ages and numerical glacier modeling results showing that mountain glaciers in the northern Rockies abandoned terminal moraines after the end of the Last Glacial Maximum around 17–18 ka and could have been sustained by −10 to −8.5 °C temperature depressions relative to modern assuming similar or drier than modern precipitation. Additionally, we present a deglacial chronology from the northern Rocky Mountains that indicates while there is considerable variability in initial moraine abandonment ages across the Rocky Mountains, the pace of subsequent ice retreat through the Lateglacial exhibits some regional coherence. Our results provide insight on potential regional mechanisms driving the initiation of and sustained deglaciation in the western U.S. including rising atmospheric CO2 and ice sheet collapse.

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