scholarly journals Ice Scours in the Sediments of Glacial Lake Iroquois, Prince Edward County, Eastern Ontario

2007 ◽  
Vol 46 (2) ◽  
pp. 189-194 ◽  
Author(s):  
Robert Gilbert ◽  
Karen J. Handford ◽  
John Shaw
Keyword(s):  
Shallow Water ◽  
Ice Sheet ◽  
Ground Surface ◽  
Laurentide Ice Sheet ◽  
Glacial Lake ◽  
Lake Ice ◽  
Prince Edward County ◽  
Westerly Direction ◽  
Eastern Ontario

ABSTRACT Straight or slightly curved ice scours are found in thin glacilacustrine sediment of eastern Lake Iroquois, especially near the crest of an escarpment in Prince Edward County. They are large (to 3.57 km long and 174 m wide), shallow (about 1 m deep) and oriented in a nearly westerly direction. Irregular ridges of sediment have been pushed up along the sides and at the western end of some scours. Bedrock is near the ground surface, but had little influence on the formation of the scours. Based on their shape, location and pattern, we conclude that the scours were most likely formed in shallow water of the short-lived Sydney phase of Lake Iroquois by lake ice driven by prevailing northeasterly winds from the retreating Laurentide Ice Sheet.

Sedimentology, stratigraphy, and geomorphology of glacial Lake Calgary at Cochrane, Alberta, Canada

1999 ◽  
Vol 36 (5) ◽  
pp. 791-803 ◽  
Author(s):  
Timothy G Fisher
Keyword(s):  
Field Data ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Glacial Lake ◽  
Fluvial Sediment

Stratigraphic and sedimentologic field data in the Cochrane, Alberta, area demonstrate that glaciolacustrine sediment comprising the Calgary Formation underlies glaciofluvial and fluvial sediment of the Bighill Creek Formation, previously dated at 11.4 ka BP. A continuous, conformable contact between sediments of glacial Lake Calgary and underlying till indicates that the lake was coeval with initial deglaciation of the area. The lake formed during retreat of the Cordilleran ice up the Bow Valley that was once previously coalescent with the Laurentide Ice Sheet. Rhythmic, graded, and convoluted glaciolacustrine sediments record continuous and high rates of sedimentation in this reach of glacial Lake Calgary, further implying that the lake formed early in deglacial time.

Pleistocene Molluscs from Lake Iroquois Deposits in Ontario

1972 ◽  
Vol 9 (5) ◽  
pp. 589-595 ◽  
Author(s):  
P. F. Karrow ◽  
A. H. Clarke ◽  
H. B. Herrington
Keyword(s):  
Shallow Water ◽  
Glacial Lake ◽  
Freshwater Snails ◽  
Lake Algonquin ◽  
Water Conditions ◽  
Eastern Ontario ◽  
Shallow Water Sediments ◽  
River Mouths

Nearly 30 taxa of Pleistocene freshwater snails and sphaeriids have been found in recent years at eight localities in glacial Lake Iroquois deposits. Older reports of molluscs from Lake Iroquois deposits by Ami (1900) and Coleman (1899, 1933) probably represent confusion with shells from Lake Algonquin and Wisconsinan interstadial deposits at Toronto.Molluscs are most abundant in shallow-water sediments deposited in former lagoons and near former river mouths in Lake Iroquois. A northeastward limit of occurrences near Oshawa, Ontario may reflect the influence of the retreating ice-margin in eastern Ontario 12 000 years ago. Shells have been found occasionally in deposits of lower level, post-Iroquois (but pre-Champlain Sea) lake stages in eastern Ontario. The Lake Iroquois fauna suggests the presence of vegetation both on land and in the water with water conditions at individual sites varying from oligotrophic to eutrophic.

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

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

<p>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 <sup>10</sup>Be 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 <sup>10</sup>Be 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.</p>

Evidence of late glacial paleoseismicity from submarine landslide deposits within Lac Dasserat, northwestern Quebec, Canada

2016 ◽  
Vol 86 (2) ◽  
pp. 184-199 ◽  
Author(s):  
Gregory R. Brooks
Keyword(s):  
Ice Sheet ◽  
Late Glacial ◽  
Relative Strength ◽  
Submarine Landslide ◽  
Laurentide Ice Sheet ◽  
Glacial Lake ◽  
Event Horizons ◽  
Lake Ojibway

AbstractAn integrated seismo- and chronostratigraphic investigation at Lac Dasserat, northwestern Quebec, identified 74 separate failures within eight event horizons. Horizons E and B, and H and G have strong or moderately-strong multi-landslide signatures, respectively, composed of 11-23 failures, while horizons F, D, C, and A have minor landslide signatures consisting of a single or pair of deposit(s). Cores collected at six sites recovered glacial Lake Ojibway varve deposits that are interbedded with the event horizons. The correlation of the varves to the regional Timiskaming varve series allowed varve ages or ranges of varve ages to be determined for the event horizons. Horizons H, G, E, and B are interpreted to be evidence of paleoearthquakes with differing levels of interpretative confidence, based on the relative strength of the multi-landslide signatures, the correlation to other disturbed deposits of similar age in the region, and the lack or possibility of alternative aseismic mechanisms. The four interpreted paleoearthquakes occurred between 9770 ± 200 and 8470 ± 200 cal yr BP, when glacial Lake Ojibway was impounded behind the Laurentide Ice Sheet during deglaciation. They probably represent an elevated period of seismicity at deglaciation that was driven by crustal unloading.

scholarly journals Laurentide Ice Sheet basal temperatures during the last glacial cycle as inferred from borehole data

2016 ◽  
Vol 12 (1) ◽  
pp. 115-127 ◽  
Author(s):  
C. Pickler ◽  
H. Beltrami ◽  
J.-C. Mareschal
Keyword(s):  
Ice Sheet ◽  
Internal Heat ◽  
Ground Surface ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Ice Streams ◽  
Borehole Data ◽  
Last Glacial ◽  
Central Canada ◽  
The Last Glacial

Abstract. Thirteen temperature–depth profiles ( ≥  1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the last glacial cycle. The sites are located in the southern part of the region that was covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 °C throughout the last glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the last glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.

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